Healthy Housing Reference Manual - CDC

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U.S. Department of Health and Human Services
U.S. Department of Housing and Urban Development
Suggested citation: Centers for Disease Control and Prevention and U.S. Department
of Housing and Urban Development. Healthy housing reference manual. Atlanta:
US Department of Health and Human Services; 2006.
Use of trade names is for identification only and does not imply endorsement by
the Centers for Disease Control and Prevention, the Public Health Service,
the U.S. Department of Health and Human Services,
or the U.S. Department of Housing and Urban Development.
Cover: Large photo by Teresa M. Sims; small photo by Don W. Johnson.
Additional copies of this manual can be downloaded from
www.cdc.gov/healthyhomes/publications.html
iiiContentsHealthy Housing Reference Manual
Contents
Preface ........................................................................................................................................................................... 1
Acknowledgments ......................................................................................................................................................... 3
Abbreviations and Acronyms ......................................................................................................................................... 5
Definitions .................................................................................................................................................................... 7
Standards and Organizations ....................................................................................................................................... 11
Executive Summary ..................................................................................................................................................... 15
Chapter 1: Housing History and Purpose ...................................................................... 1-1
Introduction ...............................................................................................................................................................1-1
Preurban Housing ......................................................................................................................................................1-1
Ephemeral Dwellings ........................................................................................................................................... 1-1
Episodic Dwellings ............................................................................................................................................... 1-1
Periodic Dwellings................................................................................................................................................ 1-1
Seasonal Dwellings ............................................................................................................................................... 1-2
Semipermanent Dwellings .................................................................................................................................... 1-2
Permanent Dwellings ........................................................................................................................................... 1-2
Urbanization ..............................................................................................................................................................1-2
Trends in Housing ......................................................................................................................................................1-3
References ..................................................................................................................................................................1-7
Additional Sources of Information ............................................................................................................................1-7
Chapter 2: Basic Principles of Healthy Housing ............................................................ 2-1
Introduction ...............................................................................................................................................................2-1
Fundamental Physiologic Needs ................................................................................................................................2-1
Fundamental Psychologic Needs.................................................................................................................................2-3
Protection Against Disease ........................................................................................................................................2-3
Protection Against Injury ...........................................................................................................................................2-5
Protection Against Fire ...............................................................................................................................................2-6
Fire Extinguishers ................................................................................................................................................. 2-8
Protection Against Toxic Gases ...................................................................................................................................2-9
References ..................................................................................................................................................................2-9
Additional Sources of Information ..........................................................................................................................2-10
Chapter 3: Housing Regulations .................................................................................. 3-1
Introduction ...............................................................................................................................................................3-1
History ......................................................................................................................................................................3-1
Zoning, Housing Codes, and Building Codes ............................................................................................................3-2
Zoning and Zoning Ordinances ........................................................................................................................... 3-3
Exceptions to the Zoning Code ............................................................................................................................ 3-5
Housing Codes ..................................................................................................................................................... 3-6
Building Codes................................................................................................................................................... 3-11
References ................................................................................................................................................................3-12
Additional Sources of Information ...........................................................................................................................3-12
Healthy Housing Reference Manualiv Contents
Chapter 4: Disease Vectors and Pests ........................................................................... 4-1
Introduction ...............................................................................................................................................................4-1
Disease Vectors and Pests ...........................................................................................................................................4-1
Rodents ................................................................................................................................................................ 4-1
Cockroaches ........................................................................................................................................................ 4-4
Fleas ..................................................................................................................................................................... 4-6
Flies ...................................................................................................................................................................... 4-7
Termites .............................................................................................................................................................. 4-8
Fire Ants............................................................................................................................................................. 4-12
Mosquitoes ........................................................................................................................................................ 4-15
References ...............................................................................................................................................................4-17
Chapter 5: Indoor Air Pollutants and Toxic Materials ..................................................... 5-1
Introduction ...............................................................................................................................................................5-1
Indoor Air Pollution ...................................................................................................................................................5-1
Biologic Pollutants ............................................................................................................................................... 5-1
Chemical Pollutants ............................................................................................................................................. 5-6
Toxic Materials .........................................................................................................................................................5-13
Asbestos ............................................................................................................................................................. 5-13
Lead ................................................................................................................................................................... 5-14
Arsenic ............................................................................................................................................................... 5-18
References ................................................................................................................................................................5-19
Chapter 6: Housing Structure ...................................................................................... 6-1
Introduction ...............................................................................................................................................................6-1
Foundation ................................................................................................................................................................6-7
Vapor Barriers ............................................................................................................................................................6-9
Crawl Space Vapor Barriers .................................................................................................................................. 6-9
Vapor Barriers for Concrete Slab Homes .............................................................................................................. 6-9
Wall and Ceiling Vapor Barriers ........................................................................................................................... 6-9
House Framing.........................................................................................................................................................6-10
Foundation Sills ................................................................................................................................................. 6-10
Flooring Systems ................................................................................................................................................ 6-10
Studs .................................................................................................................................................................. 6-10
Interior Walls ..................................................................................................................................................... 6-10
Stairways ............................................................................................................................................................ 6-11
Windows ............................................................................................................................................................ 6-11
Doors ................................................................................................................................................................. 6-13
Roof Framing ...........................................................................................................................................................6-14
Rafters ................................................................................................................................................................ 6-14
Collar Beam ....................................................................................................................................................... 6-14
Purlin ................................................................................................................................................................. 6-14
Ridge Board ....................................................................................................................................................... 6-15
Hip .................................................................................................................................................................... 6-15
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Roof Sheathing ................................................................................................................................................... 6-15
Dormer .............................................................................................................................................................. 6-15
Roofs ........................................................................................................................................................................6-15
Asphalt Shingle .................................................................................................................................................. 6-15
EPDM .............................................................................................................................................................. 6-15
Asphalt Built-up Roofs ....................................................................................................................................... 6-15
Coal Tar Pitch Built-up Roofs ............................................................................................................................ 6-15
Slate Roofs ......................................................................................................................................................... 6-15
Tile Roofs ........................................................................................................................................................... 6-15
Copper Roofs ..................................................................................................................................................... 6-15
Galvanized Iron Roofs ........................................................................................................................................ 6-15
Wood Shingle Roofs ........................................................................................................................................... 6-15
Roof Flashing ..................................................................................................................................................... 6-15
Gutters and Leaders ........................................................................................................................................... 6-16
Exterior Walls and Trim ............................................................................................................................................6-16
Putting It All Together ..............................................................................................................................................6-16
References ................................................................................................................................................................6-21
Additional Sources of Information ...........................................................................................................................6-21
Chapter 7: Environmental Barriers ............................................................................... 7-1
Introduction ...............................................................................................................................................................7-1
Roof ...........................................................................................................................................................................7-2
Insulation ...................................................................................................................................................................7-2
Siding .........................................................................................................................................................................7-3
Fiber Cement ....................................................................................................................................................... 7-4
Brick .................................................................................................................................................................... 7-4
Stucco .................................................................................................................................................................. 7-4
Vinyl ................................................................................................................................................................... 7-4
Asbestos ............................................................................................................................................................... 7-5
Metal .................................................................................................................................................................... 7-5
References ..................................................................................................................................................................7-5
Chapter 8: Rural Water Supplies and Water-quality Issues ............................................. 8-1
Introduction ...............................................................................................................................................................8-1
Water Sources .............................................................................................................................................................8-1
Source Location .........................................................................................................................................................8-2
Well Construction ......................................................................................................................................................8-3
Sanitary Design and Construction ....................................................................................................................... 8-4
Pump Selection .................................................................................................................................................... 8-4
Dug and Drilled Wells ................................................................................................................................................8-4
Springs ................................................................................................................................................................ 8-6
Cisterns ................................................................................................................................................................ 8-6
Disinfection of Water Supplies ...................................................................................................................................8-7
Chlorine Carrier Solutions ................................................................................................................................... 8-9
Routine Water Chlorination (Simple) .................................................................................................................. 8-9
Healthy Housing Reference Manualvi Contents
Well Water Shock Chlorination ............................................................................................................................ 8-9
Backflow, Back-siphonage, and Other Water Quality Problems ..................................................................................8-9
Backflow .............................................................................................................................................................. 8-9
Back-Siphonage .................................................................................................................................................. 8-10
Other Water Quality Problems ........................................................................................................................... 8-10
Protecting the Groundwater Supply ........................................................................................................................8-10
References ................................................................................................................................................................8-10
Additional Sources of Information ...........................................................................................................................8-12
Chapter 9: Plumbing .................................................................................................. 9-1
Introduction ...............................................................................................................................................................9-1
Elements of a Plumbing System ................................................................................................................................9-1
Water Service ....................................................................................................................................................... 9-1
Hot and Cold Water Main Lines .......................................................................................................................... 9-4
Water Heaters....................................................................................................................................................... 9-7
Drainage System .................................................................................................................................................. 9-8
Corrosion Control ....................................................................................................................................................9-12
Water Conservation ..................................................................................................................................................9-13
Putting It All Together ..............................................................................................................................................9-14
References ................................................................................................................................................................9-15
Additional Sources of Information ...........................................................................................................................9-16
Chapter 10: On-site Wastewater Treatment ................................................................ 10-1
Introduction .............................................................................................................................................................10-1
Treatment of Human Waste .....................................................................................................................................10-1
On-site Wastewater Treatment Systems ....................................................................................................................10-3
Septic Tank Systems ........................................................................................................................................... 10-3
Alternative Septic Tank Systems ........................................................................................................................ 10-6
Maintaining On-site Wastewater Treatment Systems ................................................................................................10-8
Symptoms of Septic System Problems ................................................................................................................ 10-9
Septic Tank Inspection ....................................................................................................................................... 10-9
References ..............................................................................................................................................................10-11
Additional Sources of Information .........................................................................................................................10-11
Chapter 11: Electricity ............................................................................................. 11-1
Introduction .............................................................................................................................................................11-1
Flow of Electric Current ...........................................................................................................................................11-2
Electric Service Entrance ..........................................................................................................................................11-3
Service Drop ...................................................................................................................................................... 11-3
Underground Service .......................................................................................................................................... 11-4
Electric Meter ..................................................................................................................................................... 11-4
Grounding ...............................................................................................................................................................11-4
Two- or Three-wire Electric Services .........................................................................................................................11-6
Residential Wiring Adequacy ...................................................................................................................................11-6
Wire Sizes and Types ................................................................................................................................................11-6
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Reducing Risk .................................................................................................................................................... 11-7
Wire Sizes ........................................................................................................................................................... 11-7
Wire Types ......................................................................................................................................................... 11-8
Types of Cable ..........................................................................................................................................................11-8
Flexible Cords ..........................................................................................................................................................11-8
The Problem ....................................................................................................................................................... 11-9
The Standards ..................................................................................................................................................... 11-9
Safety Suggestions .............................................................................................................................................. 11-9
Wiring ...................................................................................................................................................................11-10
Open Wiring .................................................................................................................................................... 11-10
Concealed Knob and Tube Wiring ................................................................................................................... 11-10
Electric Service Panel ..............................................................................................................................................11-10
Over-current Devices .............................................................................................................................................11-10
Circuit Breakers (Fuseless Service Panels) ......................................................................................................... 11-11
Ground Fault Circuit Interrupters ................................................................................................................... 11-11
Arc-fault Circuit Interrupters .......................................................................................................................... 11-11
Fused Ampere Service Panel (Fuse Box) ............................................................................................................ 11-12
Electric Circuits ......................................................................................................................................................11-13
Outlet Switches and Junction Boxes ................................................................................................................. 11-13
Grounding Outlets ........................................................................................................................................... 11-13
Polarized Plugs and Connectors ........................................................................................................................ 11-14
Common Electrical Violations ...............................................................................................................................11-14
Excessive or Faulty Fusing ................................................................................................................................ 11-15
Cords Run Through Walls or Doorways and Hanging Cords or Wires ............................................................. 11-15
Temporary Wiring ............................................................................................................................................ 11-15
Excessively Long Extension Cords .................................................................................................................... 11-15
Dead or Dummy Outlets ................................................................................................................................. 11-15
Aluminum Wiring Inside the Home ................................................................................................................ 11-15
Inspection Steps .....................................................................................................................................................11-15
References ..............................................................................................................................................................11-16
Additional Sources of Information .........................................................................................................................11-16
Chapter 12: Heating, Air Conditioning, and Ventilating............................................... 12-1
Introduction .............................................................................................................................................................12-1
Heating ....................................................................................................................................................................12-4
Standard Fuels .................................................................................................................................................... 12-4
Central Heating Units ........................................................................................................................................ 12-7
Space Heaters ................................................................................................................................................... 12-12
Hydronic Systems ............................................................................................................................................ 12-14
Direct Vent Wall Furnaces ................................................................................................................................ 12-14
Cooling ..................................................................................................................................................................12-14
Air Conditioning .............................................................................................................................................. 12-14
Circulation Fans ............................................................................................................................................... 12-16
Evaporation Coolers ......................................................................................................................................... 12-16
Healthy Housing Reference Manualviii Contents
Safety .....................................................................................................................................................................12-16
Chimneys ........................................................................................................................................................ 12-17
Fireplaces.......................................................................................................................................................... 12-17
References ..............................................................................................................................................................12-18
Additional Sources of Information .........................................................................................................................12-19
Chapter 13: Energy Efficiency ................................................................................... 13-1
Introduction .............................................................................................................................................................13-1
Energy Systems ........................................................................................................................................................13-1
R-values ...................................................................................................................................................................13-1
Roofs ........................................................................................................................................................................13-2
Ridge Vents ........................................................................................................................................................ 13-2
Fan-powered Attic Ventilation ............................................................................................................................ 13-3
White Roof Surface ............................................................................................................................................ 13-3
Insulation .................................................................................................................................................................13-3
Wall Insulation ................................................................................................................................................... 13-4
Floor Insulation .................................................................................................................................................. 13-4
Doors ................................................................................................................................................................. 13-5
Hot Water Systems ............................................................................................................................................. 13-6
Windows ..................................................................................................................................................................13-7
Caulking and Weather-Stripping ....................................................................................................................... 13-7
Replacing Window Frames ................................................................................................................................ 13-7
Tinted Windows ................................................................................................................................................ 13-7
Reducing Heat Loss and Condensation ...................................................................................................................13-7
Glazing ............................................................................................................................................................... 13-8
Layering ............................................................................................................................................................. 13-8
Other Options ................................................................................................................................................... 13-9
Solar Energy .............................................................................................................................................................13-9
Active Solar Systems ........................................................................................................................................... 13-9
Passive Solar Systems .......................................................................................................................................... 13-9
Conducting an Energy Audit ..................................................................................................................................13-10
References ..............................................................................................................................................................13-10
Additional Sources of Information .........................................................................................................................13-11
Chapter 14: Residential Swimming Pools and Spas ..................................................... 14-1
Introduction ............................................................................................................................................................14-1
Childproofing .........................................................................................................................................................14-1
Hazards ...................................................................................................................................................................14-2
Public Health Issues ................................................................................................................................................14-2
Diseases .............................................................................................................................................................. 14-3
Injuries ............................................................................................................................................................... 14-3
Water Testing Equipment .........................................................................................................................................14-3
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Disinfection ............................................................................................................................................................14-4
Content Turnover Rate .............................................................................................................................................14-4
Filters .......................................................................................................................................................................14-4
High-rate Sand Filters ....................................................................................................................................... 14-4
Cartridge Filters ................................................................................................................................................. 14-5
Diatomaceous Earth .......................................................................................................................................... 14-5
Filter Loading Rates ........................................................................................................................................... 14-5
Disinfectants ............................................................................................................................................................14-5
Effect of pH ...................................................................................................................................................... 14-6
Pool Water Hardness and Alkalinity ........................................................................................................................14-8
Liquid Chemical Feeders ..........................................................................................................................................14-8
Positive Displacement Pump .............................................................................................................................. 14-8
Erosion and Flow-through Disinfectant Feeders ................................................................................................. 14-8
Spas and Hot Tubs ...................................................................................................................................................14-9
References ..............................................................................................................................................................14-10
Additional Sources of Information .........................................................................................................................14-11
Healthy Housing Reference Manualx Contents
List of Figures
Chapter 1: Housing History and Purpose ...................................................................... 1-1
Figure 1.1. Conditions in the Tenements .................................................................................................................... 1-3
Figure 1.2. Levittown, New York ................................................................................................................................ 1-6
Chapter 2: Basic Principles of Healthy Housing ............................................................ 2-1
Figure 2.1. Circa 1890 Icebox ................................................................................................................................... 2-5
Figure 2.2. Smoke Alarm Testing ................................................................................................................................ 2-8
Chapter 3: Housing Regulations .................................................................................. 3-1
Figure 3.1. Example of a Floor Area ........................................................................................................................... 3-5
Figure 3.2. Example of an Angle of Light Obstruction ............................................................................................... 3-5
Chapter 4: Disease Vectors and Pests ........................................................................... 4-1
Figure 4.1. Field Identification of Domestic Rodents ................................................................................................. 4-2
Figure 4.2. Norway Rat .............................................................................................................................................. 4-2
Figure 4.3. Roof Rat ................................................................................................................................................... 4-2
Figure 4.4. Signs of Rodent Infestation ....................................................................................................................... 4-3
Figure 4.5. Rodent Prevention .................................................................................................................................... 4-4
Figure 4.6. Live Traps for Rats .................................................................................................................................... 4-4
Figure 4.7. Kill Traps for Rats ..................................................................................................................................... 4-4
Figure 4.8. American, Oriental, German, and Brown-banded Cockroaches ................................................................ 4-5
Figure 4.9. American Cockroaches, Various Stages and Ages ...................................................................................... 4-5
Figure 4.10. Oriental Cockroaches, Various Stages and Ages ...................................................................................... 4-5
Figure 4.11. German Cockroaches, Various Stages and Ages ....................................................................................... 4-5
Figure 4.12. Brown-banded Cockroaches, Various Stages and Ages ............................................................................ 4-5
Figure 4.13. Wood Cockroach, Adult Male ................................................................................................................ 4-5
Figure 4.14. Reported Human Plague Cases (1970–1997) ........................................................................................ 4-6
Figure 4.15. Flea Life Cycle ........................................................................................................................................ 4-6
Figure 4.16. Housefly [Musca domestica] .................................................................................................................... 4-7
Figure 4.17. Life Cycle of the Fly ............................................................................................................................... 4-8
Figure 4.18. Termite Tube Extending from Ground to Wall ....................................................................................... 4-9
Figure 4.19. Termite Mud Shelter Tube Constructed Over a Brick Foundation .......................................................... 4-9
Figure 4.20a. Ant (Elbowed Antennae: Fore Wings Larger Than Hind; Constricted Waist) ........................................ 4-9
Figure 4.20b. Termite (Beaded Antennae; All Wings Equal) ....................................................................................... 4-9
Figure 4.21. Life Cycle of the Subterranean Termite ................................................................................................. 4-10
Figure 4.22. Subterranean Termite Risk in the United States .................................................................................... 4-11
Figure 4.23. Typical Points of Attack by Termites in the Home ................................................................................ 4-12
Figure 4.24. Construction Techniques That Discourage Termite Attacks .................................................................. 4-14
Figure 4.25. Fire Ants ............................................................................................................................................... 4-14
Figure 4.26. Range Expansion of Red Imported Fire Ants [RIFAs] in the United States, 1918–1998 ....................... 4-15
Figure 4.27. Fire Ant Mound ................................................................................................................................... 4-15
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Chapter 5: Indoor Air Pollutants and Toxic Materials ..................................................... 5-1
Figure 5.1. Mold Growth in the Home ...................................................................................................................... 5-6
Figure 5.2. Home Carbon Monoxide Monitor ........................................................................................................... 5-7
Figure 5.3. Environmental Tobacco Smoke and Children’s Exposure .......................................................................... 5-8
Figure 5.4. Wood Products Label ............................................................................................................................... 5-9
Figure 5.5. EPA Map of Radon Zones ..................................................................................................................... 5-10
Figure 5.6. Radon Entry .......................................................................................................................................... 5-10
Figure 5.7. Home Radon Detectors ......................................................................................................................... 5-11
Figure 5.8. Radon-resistant Construction ................................................................................................................ 5-11
Figure 5.9. Arsenic Label ......................................................................................................................................... 5-19
Chapter 6: Housing Structure ...................................................................................... 6-1
Figure 6.1. Housing Structure Terminology, Typical House Being Built Today .......................................................... 6-1
Figure 6.2. Housing Structure and Terminology, Typical House Built Between 1950 and 1980 ................................. 6-5
Figure 6.3. Foundation .............................................................................................................................................. 6-8
Figure 6.4. Foundation Cracks .................................................................................................................................. 6-8
Figure 6.5. Interior Stairway .................................................................................................................................... 6-11
Figure 6.6. Classifications of Windows .................................................................................................................... 6-12
Figure 6.7. Three Dimensional View of a Window .................................................................................................. 6-12
Figure 6.8. Window Details .................................................................................................................................... 6-12
Figure 6.9. Wall Framing ......................................................................................................................................... 6-16
Chapter 7: Environmental Barriers ............................................................................... 7-1
Figure 7.1. Sources of Moisture and Air Pollutants .................................................................................................... 7-1
Figure 7.2. Blown Attic Insultation ........................................................................................................................... 7-3
Figure 7.3. Depth of Attic Insulation ........................................................................................................................ 7-3
Figure 7.4. Attic ventilation ....................................................................................................................................... 7-3
Figure 7.5. Brick Structural Defect ............................................................................................................................. 7-4
Figure 7.6. Corrosion in Piping Resulting From Galvanic Response ........................................................................... 7-5
Chapter 8: Rural Water Supplies and Water-quality Issues ............................................. 8-1
Figure 8.1. U.S. Water Supply by Source ................................................................................................................... 8-1
Figure 8.2. Cross Section of a Driven Well ................................................................................................................. 8-3
Figure 8.3. Well Seal ................................................................................................................................................... 8-4
Figure 8.4. Converted Dug Well ................................................................................................................................ 8-4
Figure 8.5. Recapped and Sealed Dug Well ............................................................................................................... 8-5
Figure 8.6. Drilled Well ............................................................................................................................................. 8-5
Figure 8.7. Typical Dug Well ..................................................................................................................................... 8-5
Figure 8.8. Sewage in Drainage Ditch ....................................................................................................................... 8-6
Figure 8.9. Drilled Well ............................................................................................................................................. 8-6
Figure 8.10. Spring Box ............................................................................................................................................. 8-6
Chapter 9: Plumbing .................................................................................................. 9-1
Figure 9.1. Typical Home Water System .................................................................................................................... 9-1
Figure 9.2. House Service Installation ........................................................................................................................ 9-2
Figure 9.3. Gas Water Heater .................................................................................................................................... 9-7
Healthy Housing Reference Manualxii Contents
Figure 9.4. Temperature-Pressure Valve ...................................................................................................................... 9-8
Figure 9.5. Branch Connections .............................................................................................................................. 9-10
Figure 9.6. P-trap .................................................................................................................................................... 9-10
Figure 9.7. Types of S-traps ..................................................................................................................................... 9-10
Figure 9.8. Trap Seal ................................................................................................................................................ 9-10
Figure 9.9. Loss of Trap Seal in Lavatory Sink ......................................................................................................... 9-11
Figure 9.10. Back-to-back Venting [Toilet] ............................................................................................................... 9-11
Figure 9.11. Back-to-back Venting [Sink] ................................................................................................................. 9-11
Figure 9.12. Wall-hung Fixtures .............................................................................................................................. 9-12
Figure 9.13. Unit Vent Used in Bathtub Installation ................................................................................................. 9-12
Figure 9.14. Toilet Venting ....................................................................................................................................... 9-12
Figure 9.15. Janitor’s Sink ........................................................................................................................................ 9-13
Figure 9.16. Common Y-trap ................................................................................................................................... 9-13
Figure 9.17. Hose Bib With Vacuum Breaker ........................................................................................................... 9-13
Chapter 10: On-site Wastewater Treatment ................................................................ 10-1
Figure 10.1. Conventional On-site Septic System . ................................................................................................... 10-1
Figure 10.2. Straight Pipe Discharge......................................................................................................................... 10-2
Figure 10.3. Clear Creek Water Contaminated With Sewage .................................................................................... 10-2
Figure 10.4. Septic Tank System .............................................................................................................................. 10-3
Figure 10.5. Septic Tank .......................................................................................................................................... 10-4
Figure 10.6. On-site Sewage Disposal System Site Evaluation Form ......................................................................... 10-5
Figure 10.7. Cross-section of an Absorption Field ................................................................................................... 10-5
Figure 10.8. Mound System Cutaway ...................................................................................................................... 10-7
Figure 10.9. Low Pressure On-site System ............................................................................................................... 10-7
Figure 10.10. Plant-rock Filter system ..................................................................................................................... 10-8
Figure 10.11. Sludge and Scum in Multicompartment Septic Tank ....................................................................... 10-10
Chapter 11: Electricity ............................................................................................. 11-1
Figure 11.1. Utility Overview .................................................................................................................................. 11-3
Figure 11.2. Entrance Head ..................................................................................................................................... 11-3
Figure 11.3. Armored Cable Service Entrance ......................................................................................................... 11-4
Figure 11.4. Breakers ............................................................................................................................................... 11-4
Figure 11.5. Thin-wall Conduit .............................................................................................................................. 11-4
Figure 11.6. Electric Meter ....................................................................................................................................... 11-5
Figure 11.7. Typical Service Entrance ...................................................................................................................... 11-5
Figure 11.8. Grounding Scheme .............................................................................................................................. 11-6
Figure 11.9. Grounding ........................................................................................................................................... 11-6
Figure 11.10. Three-wire Service ............................................................................................................................. 11-7
Figure 11.11. Two-wire Service ................................................................................................................................ 11-7
Figure 11.12. Wire Markings .................................................................................................................................. 11-8
Figure 11.13. Armored Cable .................................................................................................................................. 11-9
Figure 11.14. 200-Amp Service Box ...................................................................................................................... 11-10
Figure 11.15. External Power Shutoff and Meter ................................................................................................... 11-10
xiiiContentsHealthy Housing Reference Manual
Figure 11.16. GFCI ............................................................................................................................................... 11-11
Figure 11.17. Arc Interrupter ................................................................................................................................ 11-12
Figure 11.18. Types of Fuses .................................................................................................................................. 11-12
Figure 11.19. Appliance Ground and Grounded Plug ........................................................................................... 11-14
Chapter 12: Heating, Air Conditioning, and Ventilating............................................... 12-1
Figure 12.1. Heat Pump in Cooling Mode .............................................................................................................. 12-5
Figure 12.2. Piping Hookup for Inside Tank Installation ......................................................................................... 12-6
Figure 12.3. Piping Hookup for Buried Outside Tank ............................................................................................. 12-6
Figure 12.4. Minimum Clearance for Pipeless Hot Air and Gravity Warm Air Furnace ........................................... 12-7
Figure 12.5. Minimum Clearance for Steam or Hot Water Boiler and Mechanical Warm-air Furnace ..................... 12-7
Figure 12.6. Heating Ducts Covered With Asbestos Insulation ................................................................................ 12-7
Figure 12.7. Typical Underfeed Coal Stoker Installation in Small Boilers ................................................................. 12-8
Figure 12.8. Cutaway View of Typical High-pressure Gun Burner ........................................................................... 12-9
Figure 12.9. Gas-fired Boiler .................................................................................................................................... 12-9
Figure 12.10. Typical Gravity One-pipe Heating System ....................................................................................... 12-10
Figure 12.11. One-pipe Gravity Water Heating System ......................................................................................... 12-11
Figure 12.12. Two-pipe Gravity Water Heating System ......................................................................................... 12-11
Figure 12.13. Warm-air Convection Furnace ......................................................................................................... 12-11
Figure 12.14. Cross-sectional View of Building Showing Forced Warm-air Heating System .................................. 12-12
Figure 12.15. Perforated-sleeve Burner .................................................................................................................. 12-13
Figure 12.16. Condition of Burner Flame with Different Rates of Fuel Flow ........................................................ 12-13
Figure 12.17. Wall and Ceiling Clearance Reduction ............................................................................................ 12-14
Figure 12.18. Draft Relation to Height of Chimney .............................................................................................. 12-14
Figure 12.19. Location and Operation of Typical Backdraft Diverter .................................................................... 12-15
Figure 12.20. Split-system Air Conditioner ........................................................................................................... 12-16
Figure 12.21. External Air-conditioning Condenser Unit ...................................................................................... 12-16
Figure 12.22. Chimney Plan ................................................................................................................................. 12-17
Figure 12.23. Fireplace Construction .................................................................................................................... 12-18
Chapter 13: Energy Efficiency ................................................................................... 13-1
Figure 13.1. Roof Components ............................................................................................................................... 13-3
Figure 13.2. Potential Effects of Radiant Barriers ..................................................................................................... 13-4
Figure 13.3. Common Floor Insulation Flaws .......................................................................................................... 13-5
Figure 13.4a. Insulation Cavity Fill, Lath ................................................................................................................. 13-6
Figure 13.4c. Insulation Cavity Fill, Metal Rods . ..................................................................................................... 13-6
Figure 13.4b. Insulation Cavity Fill, Mesh ............................................................................................................... 13-6
Figure 13.4d. Insulation Cavity Fill, Polypropylene Twine ....................................................................................... 13-6
Figure 13.5. Solar Panels .......................................................................................................................................... 13-9
Chapter 14: Residential Swimming Pools and Spas ..................................................... 14-1
Figure 14.1. Pool Cover ............................................................................................................................................ 14-2
Figure 14.2. Typical Home Pool Equipment System ................................................................................................. 14-5
Healthy Housing Reference Manualxiv Contents
List of Tables
Table 8.1. Recommended Minimum Distance Between Well and Pollution Sources (Horizontal Distance) ........ 8-2
Table 8.2. Types of Wells for Accessing Groundwater, Well Depths, and Diameters ............................................ 8-3
Table 8.3. Disinfection Methods ......................................................................................................................... 8-7
Table 8.4. Chlorination Guide for Specific Water Conditions ............................................................................. 8-8
Table 8.5. Preparing a 200-ppm Chlorine Solution ............................................................................................. 8-9
Table 8.6. Analyzing and Correction Water Quality Problems ......................................................................... 8-11
Table 9.1. Fixture Unit Values ............................................................................................................................. 9-9
Table 9.2. Sanitary House Drain Sizes ................................................................................................................ 9-9
Table 9.3. Minimum Fixture Service Pipe Diameters ........................................................................................ 9-12
Table 10.1. Mound System Advantages and Disadvantages ................................................................................. 10-6
Table 10.2. Low-pressure Pipe Systems Advantages and Disadvantages ............................................................... 10-7
Table 10.3. Plant-rock Filter Systems Advantages and Disadvantages .................................................................. 10-8
Table 10.4. Septic Tank System Troubleshooting .............................................................................................. 10-10
Table 13.1. Cost-effective Insulation R-values for Existing homes ....................................................................... 13-2
Table 13.2. Potential Effects of Radiant Barriers ................................................................................................. 13-3
Table 13.3. Floor Insulation ................................................................................................................................ 13-5
Table 14.1. Pool Water Quality Problem Solving ................................................................................................ 14-7
Table 14.2. pH Effect on Chlorine Disinfection ................................................................................................. 14-8
Table 14.3. Chlorine Use in Swimming Pools ..................................................................................................... 14-8
Table 14.4. Swimming Pool Operating Parameters ............................................................................................. 14-9
Table 14.5. Spa and Hot Tub Operating Parameters ......................................................................................... 14-10
1PrefaceHealthy Housing Reference Manual
Housing quality is key to the public’s health. Translating that simple axiom into action is the topic of this book. In the 30 years since the first edition was published, the nation’s understanding of how specific hous-ing conditions are related to disease and injury has matured and deepened. This new edition will enable public health and housing professionals to grasp our shared responsibility to ensure that our housing stock is safe, decent,
affordable, and healthy for our citizens, especially those who are particularly vulnerable and who spend more time in
the home, such as children and the elderly.
The Centers for Disease Control and Prevention and the U.S. Department of Housing and Urban Development
(HUD) have worked together with many others to discover the ways to eliminate substandard housing conditions that
harm health. For example, the advances in combating water borne diseases was possible, in part, through standardization of indoor plumbing and sewage, and the institution of federal, state and local regulations and codes. Childhood
lead poisoning has been dramatically reduced, in part, through the elimination of residential lead-based paint hazards.
Other advances have been made to protect people from carbon monoxide poisoning, falls, safety hazards, electrocution, and many other risks.
However, more must be done to control existing conditions and to understand emerging threats that remain poorly
understood. For example, nearly 18 million Americans live with the health threat of contaminated drinking water supplies, especially in rural areas where on-site wastewater systems are prevalent. Despite progress, thousands of children
still face the threat of lead poisoning from residential lead paint hazards. The increase in asthma in recent decades and
its relationship to housing conditions such as excess moisture, mold, settled dust allergens and ventilation remains the
subject of intense research. The impact of energy conservation measures on the home environment is still unfolding.
Simple affordable construction techniques and materials that minimize moisture problems and indoor air pollution,
improve ventilation, and promote durability and efficiency continue to be uncovered.
A properly constructed and maintained home is nearly timeless in its usefulness. A home is often the biggest single
investment people make. This manual will help to ensure that the investment is a sound one that promotes healthy
and safe living.
Home rehabilitation has increased significantly in the last few years and HUD has prepared a nine-part series, The
Rehab Guide, that can assist both residents and contractors in the rehabilitation process. For additional information,
go to http://www.huduser.org/publications/destech/rehabgui.html.
Preface
Healthy Housing Reference Manual2 Preface
3AcknowledgmentsHealthy Housing Reference Manual
We acknowledge the suggestions, assistance, and review of numerous individuals and organizations that went into the original and current versions of this manual. The revisions to this manual were made by a team of environmental health, housing, and public health professionals led by Professor Joe Beck, Dr. Darryl Barnett,
Dr. Gary Brown, Dr. Carolyn Harvey, Professor Worley Johnson, Dr. Steve Konkel, and Professor Charles Treser.
Individuals from the following organizations were involved in the various drafts of this manual:
• Department of Housing and Urban Development (HUD), Office of Healthy Homes and Lead Hazard Control;
• U.S. Department of Health and Human Services (HHS), Centers for Disease Control and Prevention (CDC),
National Center for Environmental Health (NCEH);
• National Healthy Homes Training Center and Network;
• National Association of Housing and Redevelopment Officials;
• Department of Building, Housing and Zoning (Allentown, Pennsylvania);
• Code Enforcement Associates (East Orange, New Jersey);
• Eastern Kentucky University (Richmond, Kentucky);
• University of Washington; Seattle (Washington); and
• Battelle Memorial Institute (Columbus, Ohio).
• Specifically, our gratitude goes to the following reviewers:
• Dr. David Jacobs, Martin Nee, and Dr. Peter Ashley, HUD;
• Pat Bohan, East Central University;
• James Larue, The House Mender Inc.;
• Ellen Tohn, ERT Associates;
• Dr. Stephen Margolis, Emory University; and
• Joseph Ponessa and Rebecca Morley, Healthy Homes Training Center.
A special thank-you for assistance from Carolyn Case-Compton, Habitat for Humanity, 123 East Main Street,
Morehead, Kentucky. Pictures of a home under construction are courtesy of Habitat for Humanity and John King,
home builder and instructor, Rowan County Technical College, Morehead, Kentucky; and Don W. Johnson, building
photographer of Habitat for Humanity.
In addition, a special thank you to CAPT Craig Shepherd and CAPT Michael Herring, Commissioned Corps, U.S.
Public Health Service, CDC/NCEH/Environmental Health Services Branch for their research and review during the
editing of this manual. Special thanks to Pamela S. Wigington and Joey L. Johnson for their hard work preparing this
manual for publication and to Teresa M. Sims for Web publication.
Acknowledgments
Healthy Housing Reference Manual4 Acknowledgments
5Abbreviations and AcronymsHealthy Housing Reference Manual
ABS acrylonitrile-butadiene-styrene
ADA Americans with Disabilities Act
AGA American Gas Association
ALA American Lung Association
ANSI American National Standards Institute
APHA American Public Health Association
ASME American Society of Mechanical Engineers
ASSE American Society of Structural Engineers
ASTM American Society for Testing Materials
ATSDR Agency for Toxic Substances and Disease Registry
AWG American Wire Gauge
AWWA American Waters Works Association
BTU British thermal unit
CDC Centers for Disease Control and Prevention
CFR Code of Federal Regulations
CGA Canadian Gas Association
CO carbon monoxide
CPR cardiopulmonary resuscitation
CPSC Consumer Product Safety Commission
CSIA Chimney Safety Institute of America
DDT dichlorodiphenyltrichlorethane
DE diatomaceous earth
DPD N,N-diethyl-p-phenylene diamine
DWV drain, waste, and vent
EIFS exterior insulation and finish system
EPA U.S. Environmental Protection Agency
EPDM ethylene propylene dieneterpolymer
ETS environmental tobacco smoke
FHA Federal Housing Administration
FM Factory Mutual
GFCI ground fault circuit interrupter
HEPA high-efficiency particulate air
HHS Health and Human Services, U.S. Department of
HSC Home Safety Council
HUD Housing and Urban Development, U.S. Department of
HVAC heating, ventilating and air conditioning
IAPMO International Association of Plumbing and Mechanical Officials
Abbreviations and Acronyms
Healthy Housing Reference Manual6 Abbreviations and Acronyms
ICC International Code Council
IPM integrated pest management
ISO International Standard Organization
kg kilogram
LPP low-pressure pipe
MPMH Military Pest Management Handbook
MSS Mechanical Standardization Society of the Valve and Fitting Industry
NCEH National Center for Environmental Health
NCI National Cancer Institute
NIA National Institute on Aging
NSF National Science Foundation
NTU nephelometric turbidity unit
ODTS organic dust toxic syndrome
OSHA Occupational Safety and Health Administration
PEX cross-formulated polyethylene
POTW publicly owned treatment works
ppm parts per million
psi pound per square inch
PVC polyvinyl chloride
PW potable water
RIFA red imported fire ant
SDWA Safe Drinking Water Act
SEER seasonal energy efficiency ratio
T&P temperature-pressure
TSP trisodium phosphate
UF urea-formaldehyde
UL Underwriters Laboratories
USCB U.S. Census Bureau
USDA U.S. Department of Agriculture
USFA U.S. Fire Administration
USGS U.S. Geological Survey
USHA United States Housing Authority
VA Veteran’s Administration
VOC volatile organic compound
XRF X-ray fluorescence
7DefinitionsHealthy Housing Reference Manual
Accessory building or structure: a detached building or structure in a secondary or subordinate capacity from the
main or principal building or structure on the same premises.
Appropriate authority/Authority having jurisdiction (AHJ): a person within the governmental structure of the
corporate unit who is charged with the administration of the appropriate code.
Ashes: the residue from burning combustible materials.
Attic: any story or floor of a building situated wholly or partly within the roof, and so designed, arranged, or built to
be used for business, storage, or habitation.
Basement: the lowest story of a building, below the main floor and wholly or partially lower than the surface of
the ground.
Building: a fixed construction with walls, foundation, and roof, such as a house, factory, or garage.
Bulk container: any metal garbage, rubbish, or refuse container having a capacity of 2 cubic yards or greater and
which is equipped with fittings for hydraulic or mechanical emptying, unloading, or removal.
Central heating system: a single system supplying heat to one or more dwelling unit(s) or more than one rooming unit.
Chimney: a vertical masonry shaft of reinforced concrete, or other approved noncombustible, heat-resisting material
enclosing one or more flues, for the purpose of removing products of combustion from solid, liquid, or gaseous fuel.
Dilapidated: in a state of disrepair or ruin and no longer adequate for the purpose or use for which it was originally
intended.
Dormitory: a building or a group of rooms in a building used for institutional living and sleeping purposes by four or
more persons.
Dwelling: any enclosed space wholly or partly used or intended to be used for living, sleeping, cooking, and eating.
(Temporary housing, as hereinafter defined, shall not be classified as a dwelling.) Industrialized housing and modular
construction that conform to nationally accepted industry standards and are used or intended for use for living, sleeping, cooking, and eating purposes shall be classified as dwellings.
Dwelling unit: a room or group of rooms located within a dwelling forming a single habitable unit with facilities used
or intended to be used by a single family for living, sleeping, cooking, and eating.
Egress: arrangements and openings to assure a safe means of exit from buildings.
Extermination: the control and elimination of insects, rodents, or other pests by eliminating their harborage places; by
removing or making inaccessible materials that may serve as their food; by poisoning, spraying, fumigating, trapping,
or any other recognized and legal pest elimination methods approved by the local or state authority having such
administrative authority. Extermination is one of the components of integrated pest management.
Fair market value: a price at which both buyers and sellers will do business.
Family: one or more individuals living together and sharing common living, sleeping, cooking, and eating facilities
(See also Household).
Flush toilet: a toilet bowl that can be flushed with water supplied under pressure and that is equipped with a watersealed trap above the floor level.
Garbage: animal and vegetable waste resulting from handling, preparation, cooking, serving, and nonconsumption
of food.
Grade: the finished ground level adjacent to a required window.
Definitions
Healthy Housing Reference Manual8 Definitions
Guest: an individual who shares a dwelling unit in a nonpermanent status for not more than 30 days.
Habitable room: a room or enclosed floor space used or intended to be used for living, sleeping, cooking or eating
purposes, excluding bathrooms, laundries, furnace rooms, pantries, kitchenettes and utility rooms of less than 50
square feet of floor space, foyers, or communicating corridors, stairways, closets, storage spaces, workshops, and hobby
and recreation areas.
Health officer: the legally designated health authority of the jurisdiction or that person’s authorized representative.
Heated water: water heated to a temperature of not less than 120°F–130°F (49°C–54°C) at the outlet.
Heating device: all furnaces, unit heaters, domestic incinerators, cooking and heating stoves and ranges, and other
similar devices.
Household: one or more individuals living together in a single dwelling unit and sharing common living, sleeping,
cooking, and eating facilities (see also Family).
Infestation: the presence within or around a dwelling of any insects, rodents, or other pests.
Integrated pest management: a coordinated approach to managing roaches, rodents, mosquitoes, and other pests that
combines inspection, monitoring, treatment, and evaluation, with special emphasis on the decreased use of toxic agents.
Kitchen: any room used for the storage and preparation of foods and containing the following equipment: sink or
other device for dishwashing, stove or other device for cooking, refrigerator or other device for cold storage of food,
cabinets or shelves for storage of equipment and utensils, and counter or table for food preparation.
Kitchenette: a small kitchen or an alcove containing cooking facilities.
Lead-based paint: any paint or coating with lead content equal to or greater than 1 milligram per square centimeter,
or 0.5% by weight.
Multiple dwelling: any dwelling containing more than two dwelling units.
Occupant: any individual, over 1 year of age, living, sleeping, cooking, or eating in or having possession of a dwelling
unit or a rooming unit; except that in dwelling units a guest shall not be considered an occupant.
Operator: any person who has charge, care, control or management of a building, or part thereof, in which dwelling
units or rooming units are let.
Ordinary summer conditions: a temperature 10°F (-12°C) below the highest recorded temperature in the locality for
the prior 10-year period.
Ordinary winter conditions: mean a temperature 15°F (-9.4°C) above the lowest recorded temperature in the locality
for the prior 10-year period.
Owner: any person who alone, jointly, or severally with others (a) shall have legal title to any premises, dwelling, or
dwelling unit, with or without accompanying actual possession thereof, or (b) shall have charge, care or control of any
premises, dwelling, or dwelling unit, as owner or agent of the owner, or as executor, administrator, trustee, or guardian
of the estate of the owner.
Permissible occupancy: the maximum number of individuals permitted to reside in a dwelling unit, rooming unit, or
dormitory.
Person: any individual, firm, corporation, association, partnership, cooperative, or government agency.
Plumbing: all of the following supplied facilities and equipment: gas pipes, gas burning equipment, water pipes,
garbage disposal units, waste pipes, toilets, sinks, installed dishwashers, bathtubs, shower baths, installed clothes washing machines, catch basins, drains, vents, and similarly supplied fixtures, and the installation thereof, together with all
connections to water, sewer, or gas lines.
9DefinitionsHealthy Housing Reference Manual
Privacy: the existence of conditions which will permit an individual or individuals to carry out an activity commenced
without interruption or interference, either by sight or sound by unwanted individuals.
Rat harborage: any conditions or place where rats can live, nest or seek shelter.
Ratproofing: a form of construction that will prevent the entry or exit of rats to or from a given space or building, or
from gaining access to food, water, or harborage. It consists of the closing and keeping closed of every opening in
foundations, basements, cellars, exterior and interior walls, ground or first floors, roofs, sidewalk gratings, sidewalk
openings, and other places that may be reached and entered by rats by climbing, burrowing, or other methods, by the
use of materials impervious to rat gnawing and other methods approved by the appropriate authority.
Refuse: leftover and discarded organic and nonorganic solids (except body wastes), including garbage, rubbish, ashes,
and dead animals.
Refuse container: a watertight container that is constructed of metal, or other durable material impervious to rodents,
that is capable of being serviced without creating unsanitary conditions, or such other containers as have been
approved by the appropriate authority (see also Appropriate Authority). Openings into the container, such as covers and
doors, shall be tight fitting.
Rooming house: any dwelling other than a hotel or motel or that part of any dwelling containing one or more rooming units, or one or more dormitory rooms, and in which persons either individually or as families are housed with or
without meals being provided.
Rooming unit: any room or group of rooms forming a single habitable unit used or intended to be used for living
and sleeping, but not for cooking purposes.
Rubbish: nonputrescible solid wastes (excluding ashes) consisting of either: (a) combustible wastes such as paper, cardboard, plastic containers, yard clippings and wood; or (b) noncombustible wastes such as cans, glass, and crockery.
Safety: the condition of being reasonably free from danger and hazards that may cause accidents or disease.
Space heater: a self-contained heating appliance of either the convection type or the radiant type and intended primarily to heat only a limited space or area such as one room or two adjoining rooms.
Supplied: paid for, furnished by, provided by, or under the control of the owner, operator or agent.
System: the dynamic interrelationship of components designed to enact a vision.
Systems theory: The concept proposed to promote the dynamic interrelationship of activities designed to accomplish
a unified system.
Temporary housing: any tent, trailer, mobile home, or other structure used for human shelter that is designed to be
transportable and which is not attached to the ground, to another structure, or to any utility system on the same
premises for more than 30 consecutive days.
Toxic substance: any chemical product applied on the surface of or incorporated into any structural or decorative
material, or any other chemical, biologic, or physical agent in the home environment or its immediate surroundings,
which constitutes a potential hazard to human health at acute or chronic exposure levels.
Variance: a difference between that which is required or specified and that which is permitted.
Healthy Housing Reference Manual10 Definitions
11Standards and OrganizationsHealthy Housing Reference Manual
In addition to the standards and organizations listed in this section, the U.S. Justice Department enforces the requirements of the Americans with Disabilities Act (ADA) (http://www.ada.gov) and assures that products fully comply with the provisions of the act to ensure equal access for physically challenged users.
ABPA The American Backflow Prevention Association, http://abpa.org
Develops cross-connections; ABPA is an organization whose members have a common interest in
protecting drinking water from contamination.
ACI American Concrete Institute, http://www.concrete.org/general/home.asp
Has produced more than 400 technical documents, reports, guides, specifications, and codes for the
best use of concrete. ACI conducts more than 125 educational seminars each year and has 13
certification programs for concrete practitioners, as well as a scholarship program to promote careers in
the industry.
AGA American Gas Association, http://www.aga.org
Develops standards, tests, and qualifies products used in gas lines and gas appliance installations.
AGC Associated General Contractors of America, http://www.agc.org
Is dedicated to improving the construction industry by educating the industry to employ the finest
skills, promoting use of the latest technology and advocating building the best quality projects for
owners— public and private.
AMSA Association of Metropolitan Sewerage Agencies, http://www.amsa-cleanwater.org
Represents the interests of the country’s wastewater treatment agencies.
ANSI American National Standards Institute, http://www.ansi.org
Coordinates work among U.S. standards writing groups. Works in conjunction with other groups such
as ISO, ASME, and ASTM.
ARI Air-Conditioning and Refrigeration Institute, http://www.ari.org
Provides information about the 21st Century Research (21-CR) initiative, a private-public sector
research collaboration of the heating, ventilation, air-conditioning, and refrigeration industry, with a
focus on energy conservation, indoor environmental quality, and environmental protection.
ASCE American Society of Civil Engineers, http://www.asce.org
Provides essential value to its members, careers, partners, and the public by developing leadership,
advancing technology, advocating lifelong learning, and promoting the profession.
ASHI The American Society of Home Inspectors, http://www.ashi.org
Is a source of information about the home inspection profession.
ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers, http://www.ashrae.org
Writes standards and guidelines that include uniform methods of testing for rating purposes, describe
recommended practices in designing and installing equipment and provide other information to guide
the industry. ASHRAE has more than 80 active standards and guideline project committees,
addressing such broad areas as indoor air quality, thermal comfort, energy conservation in buildings,
reducing refrigerant emissions, and the designation and safety classification of refrigerants.
ASME The American Society of Mechanical Engineers, http://www.asme.org
Develops standards for materials and testing as well as finished products.
ASSE American Society of Sanitary Engineering, http://www.asse.org
Develops standards and qualifies products for plumbing and sanitary installations.
ASTM American Society for Testing and Materials, http://www.astm.org
Is one of the largest voluntary standards development organizations in the world-a trusted source for
technical standards for materials, products, systems, and services.
Standards and Organizations
Healthy Housing Reference Manual12 Standards and Organizations
AWWA American Water Works Association, http://www.awwa.org
Promotes public health through improvement of the quality of water and develops standards for valves,
fittings, and other equipment.
CGA Canadian Gas Association, http://www.cga.ca
Develops standards, tests, and qualifies products used in gas lines and gas appliance installations.
CPSC U.S Consumer Product Safety Commission, http://www.cpsc.gov
Protects the public from unreasonable risks for serious injury or death from more than 15,000 types of
consumer products. CPSC is committed to protecting consumers and families from products that pose
a fire, electrical, chemical, or mechanical hazard or can injure children.
CRBT Center for Resourceful Building Technology, http://www.crbt.org
Contains the online Guide to Resource-Efficient Building Elements, which provides information about
environmentally efficient construction materials, including foundations, wall systems, panels,
insulation, siding, roofing, doors, windows, interior finishing, and floor coverings.
EPA U.S. Environmental Protection Agency, http://www.epa.gov
Protects human health and the environment.
FM Factory Mutual, http://fmglobal.com
Develops standards and qualifies products for use by the general public and develops standards for
materials, products, systems, and services.
HFHI Habitat for Humanity International, http://www.habitat.org
Is a nonprofit, ecumenical Christian housing ministry. HFHI seeks to eliminate poverty housing and
homelessness from the world, and to make decent shelter a matter of conscience and action.
HUD U.S. Department of Housing and Urban Development, http://www.hud.gov
As part of the HUD efforts toward eliminating childhood lead poisoning, the Office of Healthy
Homes and Lead Hazard Control is sharing local lead ordinances and regulations that have proven
effective in helping communities deal with lead-based paint hazards. Also, the design and construction
of manufactured housing are regulated by the federal government and must comply with HUD’s
Manufactured Home Construction and Safety Standards. Modular and panelized construction must
comply with model or local building codes.
IAPMO International Association of Plumbing and Mechanical Officials, http://www.iapmo.org
Developed and maintains the Uniform Plumbing Code and the Uniform Mechanical Code.
ICBO The Uniform Building Code (UBC)/International Conference of Building Officials,
http://www.iccsafe.org
Is the most widely adopted model building code in the world and is a proven document meeting the
needs of government units charged with enforcement of building regulation. Published triennially, the
UBC provides complete regulations covering all major aspects of building design and construction
relating to fire and life safety and structural safety. The requirements reflect the latest technologic
advances available in the building and fire- and life-safety industry.
ICC International Code Council, http://www.iccsafe.org
Produces the most widely adopted and enforced building safety codes in the United States (I-Codes).
International Residential C ode (IRC) 2003 has been adopted by many states, jurisdictions, and
localities. IRC also references several industry standards such as ACI 318, ASCE 7, ASTM, and ANSI
standards that cover specific load, load combinations, design methods, and material specifications.
ISO International Standard Organization, http://www.iso.org
Provides internationally recognized certification for manufacturers that comply with high standards of
quality control, developed standards ISO-9000 through ISO-9004, and qualifies and lists products
suitable for use in plumbing installations.
13Standards and OrganizationsHealthy Housing Reference Manual
MSS Manufacturers Standardization Society of the Valve and Fittings Industry, Inc.,
http://www.mss-hq.com
Develops technical codes and standards for the valve and fitting industry.
NACHI The National Association of Certified Home Inspectors, http://www.nachi.org/index.htm
Is the world’s largest, most elite nonprofit inspection association.
NAHB National Association of Home Builders, http://www.nahb.org
Is a trade association representing more than 220,000 residential home building and remodeling
industry members. NAHB is affiliated with more than 800 state and local home builders associations
around the country. NAHB urges codes and standards development and application that protects
public health and safety without cost impacts that decrease affordability and consequently prevent
people from moving into new, healthier, safer homes.
NEC National Electrical Code, http://www.nfpa.org
Protects public safety by establishing requirements for electrical wiring and equipment in virtually all
buildings.
NESC National Environmental Services Center, http://www.nesc.wvu.edu/nesc/nesc_about.htm
Is a repository for water, wastewater, solid waste, and environmental training research.
NFPA National Fire Protection Association, http://www.nfpa.org/index.asp
Develops, publishes, and disseminates more than 300 consensus codes and standards intended to
minimize the possibility and effects of fire and other risks.
NOWRA National Onsite Wastewater Recycling Association, http://www.nowra.org
Provides leadership and promotes the onsite wastewater treatment and recycling industry through
education, training, communication, and quality tools to support excellence in performance.
NSF National Sanitation Foundation, http://www.nsf.org
Develops standards for equipment, products and services; a nonprofit organization now known as
International.
UL Underwriters Laboratory, http://www.ul.com
Has developed more than 800 Standards for Safety. Millions of products and their components are
tested to UL’s rigorous safety standards.
WEF Water Environment Federation, http://www.wef.org
Is a not-for-profit technical and educational organization with members from varied disciplines who
work toward the WEF vision of preservation and enhancement of the global water environment. The
WEF network includes water quality professionals from 76 member associations in 30 countries.
Healthy Housing Reference Manual14 Standards and Organizations
15Executive SummaryHealthy Housing Reference Manual
Executive Summary
The original Basic Housing Inspection manual was published in 1976 by the Center for Disease Control (now known as the Centers for Disease Control and Prevention). Its Foreword stated:“The growing numbers of new families and the increasing population in the United States have created a
pressing demand for additional housing that is conducive to healthful living. These demands are increased by
the continuing loss of existing housing through deterioration resulting from age and poor maintenance. Large
numbers of communities in the past few years have adopted housing codes and initiated code enforcement
programs to prevent further deterioration of existing housing units. This growth in housing activities has
caused a serious problem for communities in obtaining qualified personnel to provide the array of housing
service needed, such as information, counseling, technical advice, inspections, and enforcement. As a result
many agencies throughout the country are conducting comprehensive housing inspection training courses.
This publication has been designed to be an integral part of these training sessions.”
The original Basic Housing Inspection manual has been successfully used for several decades by public health and
housing personnel across the United States. Although much has changed in the field of housing construction and
maintenance, and health and safety issues have expanded, the manual continues to have value, especially as it relates
to older housing.
Many housing deficiencies impact on health and safety. For example, lead-based paint and dust may contribute to
lead poisoning in children; water leakage and mold may contribute to asthma episodes; improper use and storage of
pesticides may result in unintentional poisoning; and lack of working smoke, ionization, and carbon monoxide alarms
may cause serious injury and death.
Government agencies have been very responsive to “healthy homes” issues. The U.S. Department of Housing and
Urban Development (HUD) created an office with an exclusive focus on healthy homes. In 2003, CDC joined HUD
in the effort to improve housing conditions through the training of environmental health practitioners, public health
nurses, housing specialists, and others who have interest and responsibility for creating healthy homes.
The revised Basic Housing Inspection manual, renamed the Healthy Housing Reference Manual, responds to the enormous changes that have occurred in housing construction methods and materials and to new knowledge related to the
impact of housing on health and safety. New chapters have been added, making the manual more comprehensive. For
example, an entire chapter is devoted to rural water supplies and on-site wastewater treatment. A new chapter was
added that discusses issues related to residential swimming pools and spas. At over 200 pages, the comprehensive
revised manual is designed primarily as a reference document for public health and housing professionals who work in
government and industry.
The Healthy Housing Reference Manual contains 14 chapters, each with a specific focus. All chapters contain annotated
references and a listing of sources for additional topic information. A summary of the content of each chapter follows:
Chapter One, Housing History and Purpose, describes the history of dwellings and urbanization and housing
trends during the last century.
Chapter Two, Basic Principles of Healthy Housing, describes the basic principles of healthy housing and
safety— physiologic needs, psychologic needs, protection against injury and disease— and lays the groundwork for
following chapters.
Chapter Three, Housing Regulations, reviews the history of housing regulations, followed by a discussion of
zoning, housing, and building codes.
Chapter Four, Disease Vectors and Pests, provides a detailed analysis of disease vectors that have an impact on residences. It includes information on the management of mice, rats, cockroaches, fleas, flies, termites, and fire ants.
Healthy Housing Reference Manual16 Executive Summary
Chapter Five, Indoor Air Pollution and Toxic Materials, provides information on indoor air pollution, both
biologic and chemical, and to toxic materials in the home, including methods for controlling these hazards. The
impact of cockroaches, dust mites, pets, and mold are discussed. Also included is information about the impact of
carbon monoxide, ozone, tobacco smoke, volatile organic compounds, radon, and pesticides.
Chapter Six, Housing Structure, contains information about “older” housing construction and new construction
materials and methods. The chapter also introduces new terminologies and includes information about foundations, vapor barriers, house framing, roof framing, exterior walls, and roofs.
Chapter Seven, Environmental Barriers, provides information on roofing, insulation, and siding materials.
Chapter Eight, Rural Water Supplies and Water-quality Issues, covers issues related to the drilling and proper
maintenance of wells. Research information is provided that indicates that many wells are not properly sealed,
allowing for the leakage of contaminated water into wells during hurricanes and periods of significant flooding.
Chapter Nine, Plumbing, provides information on plumbing standards and how they can be accessed, followed
by a review of the elements of a residential water delivery system, the types of available hot-water heaters, drainage
systems, and methods for water conservation. It also includes a visual synthesis of water system components during
new residential construction.
Chapter Ten, On-site Wastewater Treatment, complements chapter seven by providing information on proper
on-site methods for the treatment of human waste.
Chapter Eleven, Electricity, expands on information contained in the original manual covering such topics as
breaker systems and polarized plugs and connectors. It also provides a format for the inspection of residential
electrical systems.
Chapter Twelve, Heating, Air Conditioning, and Ventilation, provides information about types of residential
fuels and heating systems, including solar heating and minor sources of heating (e.g., coal-fired, oil-fired, gas-fired,
and electrical space heaters). Chimney and fireplace safety and the variety of cooling systems are also discussed.
Chapter Thirteen, Energy Efficiency, discusses energy efficiency, including “R” values and their interpretation,
roof ventilation, wall and floor insulation, and door and window energy efficiency systems. It also discusses active
and passive solar systems and provides a methodology for conducting a residential energy audit.
Chapter Fourteen, Residential Swimming Pools and Spas, provides information about child safety, pool and spa
hazards, and diseases. It also provides information on methods for testing and ensuring a safe water system and on
methods for spa and pool disinfection. Further, it covers concerns related to unregulated individual residential pools
and spas.
The quality of housing plays a decisive role in the health status of its occupants. Substandard housing conditions have
been linked to adverse health effects such as childhood lead poisoning, asthma and other respiratory conditions, and
unintentional injuries. This new and revised Healthy Housing Reference Manual is an important reference for anyone
with responsibility and interest in creating and maintaining healthy housing.
The housing design and construction industry has made great progress in recent years through the development of
new innovative techniques, materials technologies, and products. The HUD Rehab Guide series was developed to
inform the design and construction industry about state-of-the-art materials and innovative practices in housing rehabilitation. The series focuses on building technologies, materials, components, and techniques rather than on projects
such as adding a new room. The nine volumes each cover a distinct element of housing rehabilitation and feature
breakthrough materials, labor-saving tools, and cost-cutting practices. The nine volumes address foundations; exterior
walls; roofs; windows and doors; partitions, ceilings, floors, and stairs; kitchen and baths; electrical/electronics; heating, air conditioning, and ventilation; plumbing; and site work.
Additional information about the series can be found at http://www.huduser.org/publications/destech/rehabgui.html
and http://www.pathnet.org/sp.asp?id=997. This series is an excellent adjunct to the Healthy Housing Reference Manual.
1-1Chapter 1: Housing History and PurposeHealthy Housing Reference Manual
“Safe, affordable housing is a basic necessity for every family.
Without a decent place to live, people cannot be productive
members of society, children cannot learn and families cannot thrive.”
Tracy Kaufman, Research Associate
National Low Income Housing Coalition/
Low Income Housing Information Service
http://www.habitat.org/how/poverty.html; 2003
Introduction
The term “shelter,” which is often used to define housing,
has a strong connection to the ultimate purpose of housing throughout the world. The mental image of a shelter
is of a safe, secure place that provides both privacy and
protection from the elements and the temperature
extremes of the outside world.
This vision of shelter, however, is complex. The earthquake in Bam, Iran, before dawn on December 26, 2003,
killed in excess of 30,000 people, most of whom were
sleeping in their homes. Although the homes were made
of the most simple construction materials, many were
well over a thousand years old. Living in a home where
generation after generation had been raised should provide an enormous sense of security. Nevertheless, the
world press has repeatedly implied that the construction
of these homes destined this disaster. The homes in Iran
were constructed of sun-dried mud-brick and mud.
We should think of our homes as a legacy to future generations and consider the negative environmental effects
of building them to serve only one or two generations
before razing or reconstructing them. Homes should be
built for sustainability and for ease in future modification. We need to learn the lessons of the earthquake in
Iran, as well as the 2003 heat wave in France that killed
in excess of 15,000 people because of the lack of climate
control systems in their homes. We must use our experience, history, and knowledge of both engineering and
human health needs to construct housing that meets the
need for privacy, comfort, recreation, and health
maintenance.
Health, home construction, and home maintenance are
inseparable because of their overlapping goals. Many
highly trained individuals must work together to achieve
quality, safe, and healthy housing. Contractors, builders,
code inspectors, housing inspectors, environmental health
officers, injury control specialists, and epidemiologists all
are indispensable to achieving the goal of the best housing in the world for U.S. citizens. This goal is the basis
for the collaboration of the U.S. Department of Housing
and Urban Development (HUD) and the Centers for
Disease and Control and Prevention (CDC).
Preurban Housing
inhabitants. The housing similarities among civilizations
separated by vast distances may have been a result of a
shared heritage, common influences, or chance.
Caves were accepted as dwellings, perhaps because they
were ready made and required little or no construction.
However, in areas with no caves, simple shelters were constructed and adapted to the availability of resources and
the needs of the population. Classification systems have
been developed to demonstrate how dwelling types
evolved in preurban indigenous settings [1].
Ephemeral Dwellings
Ephemeral dwellings, also known as transient dwellings,
were typical of nomadic peoples. The African bushmen
and Australia’s aborigines are examples of societies whose
existence depends on an economy of hunting and food
gathering in its simple form. Habitation of an ephemeral
dwelling is generally a matter of days.
Episodic Dwellings
Episodic housing is exemplified by the Inuit igloo, the
tents of the Tungus of eastern Siberia, and the very similar tents of the Lapps of northern Europe. These groups
are more sophisticated than those living in ephemeral
dwellings, tend to be more skilled in hunting or fishing,
inhabit a dwelling for a period of weeks, and have a
greater effect on the environment. These groups also construct communal housing and often practice slash-andburn cultivation, which is the least productive use of
cropland and has a greater environmental impact than the
hunting and gathering of ephemeral dwellers.
Periodic Dwellings
Periodic dwellings are also defined as regular temporary
dwellings used by nomadic tribal societies living in a pastoral economy. This type of housing is reflected in the
yurt used by the Mongolian and Kirgizian groups and the
Bedouins of North Africa and western Asia. These groups’
dwellings essentially demonstrate the next step in the evolution of housing, which is linked to societal developChapter 1: Housing History and Purpose
Healthy Housing Reference Manual1-2 Chapter 1: Housing History and Purpose
ment. Pastoral nomads are distinguished from people
living in episodic dwellings by their homogenous cultures
and the beginnings of political organization. Their environmental impact increases with their increased dependence on agriculture rather than livestock.
Seasonal Dwellings
Schoenauer [1] describes seasonal dwellings as reflective of
societies that are tribal in nature, seminomadic, and based
on agricultural pursuits that are both pastoral and marginal. Housing used by seminomads for several months or
for a season can be considered semisedentary and reflective of the advancement of the concept of property, which
is lacking in the preceding societies. This concept of
property is primarily of communal property, as opposed
to individual or personal property. This type of housing is
found in diverse environmental conditions and is demonstrated in North America by the hogans and armadas of
the Navajo Indians. Similar housing can be found in
Tanzania (Barabaig) and in Kenya and Tanzania (Masai).
Semipermanent Dwellings
According to Schoenauer [1], sedentary folk societies or
hoe peasants practicing subsistence agriculture by cultivating staple crops use semipermanent dwellings. These
groups tend to live in their dwellings various amounts of
time, usually years, as defined by their crop yields. When
land needs to lie fallow, they move to more fertile areas.
Groups in the Americas that used semipermanent dwellings included the Mayans with their oval houses and the
Hopi, Zuni, and Acoma Indians in the southwestern
United States with their pueblos.
Permanent Dwellings
The homes of sedentary agricultural societies, whose
political and social organizations are defined as nations
and who possess surplus agricultural products, exemplify
this type of dwelling. Surplus agricultural products
allowed the division of labor and the introduction of
other pursuits aside from food production; however, agriculture is still the primary occupation for a significant
portion of the population. Although they occurred at different points in time, examples of early sedentary agricultural housing can be found in English cottages, such as
the Suffolk, Cornwall, and Kent cottages [1].
Urbanization
Permanent dwellings went beyond simply providing shelter and protection and moved to the consideration of
comfort. These structures began to find their way into
what is now known as the urban setting. The earliest
available evidence suggests that towns came into existence
around 4000 BC. Thus began the social and public
health problems that would increase as the population of
cities increased in number and in sophistication. In
preurban housing, the sparse concentration of people
allowed for movement away from human pollution or
allowed the dilution of pollution at its location. The
movement of populations into urban settings placed individuals in close proximity, without the benefit of previous
linkages and without the ability to relocate away from
pollution or other people.
Urbanization was relatively slow to begin, but once started,
it accelerated rapidly. In the 1800s, only about 3% of the
population of the world could be found in urban settings
in excess of 5,000 people. This was soon to change. The
year 1900 saw the percentage increase to 13.6% and subsequently to 29.8% in 1950. The world’s urban population has grown since that time. By 1975, more than one in
three of the world’s population lived in an urban setting,
with almost one out of every two living in urban areas by
1997. Industrialized countries currently find approximately 75% of their population in an urban setting. The
United Nations projects that in 2015 the world’s urban
population will rise to approximately 55% and that in
industrialized nations it will rise to just over 80%.
In the Western world, one of the primary forces driving
urbanization was the Industrial Revolution. The basic
source of energy in the earliest phase of the Industrial
Revolution was water provided by flowing rivers.
Therefore, towns and cities grew next to the great waterways. Factory buildings were of wood and stone and
matched the houses in which the workers lived, both in
construction and in location. Workers’ homes were little
different in the urban setting than the agricultural homes
from whence they came. However, living close to the
workplace was a definite advantage for the worker of the
time. When the power source for factories changed from
water to coal, steam became the driver and the construction materials became brick and cast iron, which later
evolved into steel. Increasing populations in cities and
towns increased social problems in overcrowded slums.
The lack of inexpensive, rapid public transportation
forced many workers to live close to their work. These
factory areas were not the pastoral areas with which many
were familiar, but were bleak with smoke and other
pollutants.
The inhabitants of rural areas migrated to ever-expanding
cities looking for work. Between 1861 and 1911 the population of England grew by 80%. The cities and towns of
England were woefully unprepared to cope with the
1-3Chapter 1: Housing History and PurposeHealthy Housing Reference Manual
resulting environmental problems, such as the lack of
potable water and insufficient sewerage.
In this atmosphere, cholera was rampant; and death rates
resembled those of Third World countries today. Children
had a one in six chance of dying before the age of 1 year.
Because of urban housing problems, social reformers such
as Edwin Chadwick began to appear. Chadwick’s Report
on an Enquiry into the Sanitary Condition of the Labouring
Population of Great Britain and on the Means of its
Improvement [2] sought many reforms, some of which
concerned building ventilation and open spaces around
the buildings. However, Chadwick’s primary contention
was that the health of the working classes could be
improved by proper street cleaning, drainage, sewage,
ventilation, and water supplies. In the United States,
Shattuck et al. [3] wrote the Report of the Sanitary
Commission of Massachusetts, which was printed in 1850.
In the report, 50 recommendations were made. Among
those related to housing and building issues were recommendations for protecting school children by ventilation
and sanitation of school buildings, emphasizing town
planning and controlling overcrowded tenements and cellar dwellings. Figure 1.1 demonstrates the conditions
common in the tenements.
In 1845, Dr. John H. Griscom, the City Inspector of
New York, published The Sanitary Condition of the
Laboring Population of New York [4]. His document
expressed once again the argument for housing reform
and sanitation. Griscom is credited with being the first to
use the phrase “how the other half lives.” During this
time, the poor were not only subjected to the physical
problems of poor housing, but also were victimized by
corrupt landlords and builders.
Trends in Housing
The term “tenement house” was first used in America and
dates from the mid-nineteenth century. It was often intertwined with the term “slum.” Wright [5] notes that in
English, tenement meant “an abode for a person or for
the soul, when someone else owned the property.” Slum,
on the other hand, initially was used at the beginning of
the 19th century as a slang term for a room. By the middle of the century, slum had evolved into a term for a
back dwelling occupied by the lowest members of society.
Von Hoffman [6] states that this term had, by the end of
the century, begun to be used interchangeably with tenement. The author noted that in the larger cities of the
United States, the apartment house emerged in the 1830s
as a housing unit of two to five stories, with each story
containing apartments of two to four rooms. It was originally built for the upper group of the working class. The
tenement house emerged in the 1830s when landlords
converted warehouses into inexpensive housing designed
to accommodate Irish and black workers. Additionally,
existing large homes were subdivided and new structures
were added, creating rear houses and, in the process,
eliminating the traditional gardens and yards behind
them. These rear houses, although new, were no healthier
than the front house, often housing up to 10 families.
When this strategy became inadequate to satisfy demand,
the epoch period of the tenements began.
Figure 1.1. Conditions in the Tenements
Although unpopular, the tenement house grew in numbers, and, by 1850 in New York and Boston, each tenement housed an average of 65 people. During the 1850s,
the railroad house or railroad tenement was introduced.
This structure was a solid, rectangular block with a narrow alley in the back. The structure was typically 90 feet
long and had 12 to 16 rooms, each about 6 feet by 6 feet
and holding around four people. The facility allowed no
direct light or air into rooms except those facing the street
or alley. Further complicating this structure was the lack
of privacy for the tenants. A lack of hallways eliminated
Healthy Housing Reference Manual1-4 Chapter 1: Housing History and Purpose
History of the Department of Housing and Urban Development
1934 Housing Act establishes Federal Housing Administration to insure mortgages and make loans to low-income families; Fannie Mae created.
1937 Housing Act establishes public housing.
1944 Serviceman’s Readjustment Act creates Veteran Administration mortgages; trend toward suburbia begins.
Late 1950s Urban renewal begins; slum clearance developed to promote construction of affordable housing.
1965 Department of Housing and Urban Development created.
1968 Model Cities program launched; fair housing launched through the Civil Rights Act.
1971 Lead-Based Paint Poisoning Prevention Act passed.
1974 Section 8 rental subsidy program begins; Community Development Block Grant program begins.
1977 Urban Development Action Grants begin.
1986 Low-income housing tax credit created.
1987 McKinney Homeless Assistance Act passed; creation of low-income housing tax credit.
1991–1994 Public housing inspection for lead paint.
1992 Residential Lead Hazard Reduction Act passed (Title X of the 1992 Housing and Community Development Act).
1993 Hope VI program begins to redevelop old public housing.
1996 Lead-based paint disclosure becomes law.
1999 HUD and CDC launch the Healthy Homes Initiative.
2000 HUD publishes new lead paint regulations for federally funded assisted housing; President’s Task Force releases federal interagency plan to eliminate childhood lead paint poisoning by 2010.
2001 EPA publishes final standards for lead in paint, dust, and soil in housing.
any semblance of privacy. Open sewers, a single privy in
the back of the building, and uncollected garbage resulted
in an objectionable and unhygienic place to live.
Additionally, the wood construction common at the time,
coupled with coal and wood heating, made fire an everpresent danger. As a result of a series of tenement fires in
1860 in New York, such terms as death-trap and fire-trap
were coined to describe the poorly constructed living
facilities [6].
The two last decades of the 19th century saw the introduction and development of dumbbell tenements, a front
and rear tenement connected by a long hall. These tenements were typically five stories, with a basement and no
elevator (elevators were not required for any building of
less than six stories). Dumbbell tenements, like other tenements, resulted in unaesthetic and unhealthy places to
live. Garbage was often thrown down the airshafts, natural light was confined to the first floor hallway, and the
public hallways only contained one or two toilets and a
sink. This apparent lack of sanitary facilities was compounded by the fact that many families took in boarders
to help with expenses. In fact, 44,000 families rented
space to boarders in New York in 1890, with this increasing to 164,000 families in 1910. In the early 1890s, New
York had a population of more than 1 million, of which
70% were residents of multifamily dwellings. Of this
group, 80% lived in tenements consisting mostly of
dumbbell tenements.
The passage of the New York Tenement House Act of
1901 spelled the end of the dumbbells and acceptance of
a new tenement type developed in the 1890s— the park
or central court tenement, which was distinguished by a
park or open space in the middle of a group of buildings.
This design was implemented to reduce the activity on
1-5Chapter 1: Housing History and PurposeHealthy Housing Reference Manual
the front street and to enhance the opportunity for fresh
air and recreation in the courtyard. The design often
included roof playgrounds, kindergartens, communal
laundries, and stairways on the courtyard side.
Although the tenements did not go away, reform groups
supported ideas such as suburban cottages to be developed for the working class. These cottages were two-story
brick and timber, with a porch and a gabled roof.
According to Wright [5], a Brooklyn project called
Homewood consisted of 53 acres of homes in a planned
neighborhood from which multifamily dwellings, saloons,
and factories were banned.
Although there were many large homes for the well-todo, single homes for the not-so-wealthy were not abundant. The first small house designed for the individual of
modest means was the bungalow. According to
Schoenauer [1], bungalows originated in India. The bungalow was introduced into the United States in 1880 with
the construction of a home in Cape Cod. The bungalow,
derived for use in tropical climates, was especially popular
in California.
Company towns were another trend in housing in the
19th century. George Pullman, who built railway cars in
the 1880s, and John H. Patterson, of the National Cash
Register Company, developed notable company towns.
Wright [5] notes that in 1917 the U.S. Bureau of Labor
Standards estimated that at least 1,000 industrial firms
were providing housing for their employees. The provision of housing was not necessarily altruistic. The motivation for providing housing varied from company to
company. Such motivations included the use of housing
as a recruitment incentive for skilled workers, a method
of linking the individual to the company, and a belief
that a better home life would make the employees happier and more productive in their jobs. Some companies,
such as Firestone and Goodyear, went beyond the company town and allowed their employees to obtain loans
for homes from company-established banks. A prime
motivator of company town planning was sanitation,
because maintaining the worker’s health could potentially
lead to fewer workdays lost due to illness. Thus, in the
development of the town, significant consideration was
given to sanitary issues such as window screens, sewage
treatment, drainage, and water supplies.
Before World War I there was a shortage of adequate
dwellings. Even after World War I, insufficient funding, a
shortage of skilled labor, and a dearth of building materials compounded the problem. However, the design of
homes after the war was driven in part by health considerations, such as providing good ventilation, sun orientation and exposure, potable pressurized water, and at least
one private toilet. Schoenauer [1] notes that, during the
postwar years, the improved mobility of the public led to
an increase in the growth of suburban areas, exemplified
by the detached and sumptuous communities outside
New York, such as Oyster Bay. In the meantime, the conditions of working populations consisting of many immigrants began to improve with the improving economy of
the 1920s. The garden apartment became popular. These
units were well lighted and ventilated and had a courtyard, which was open to all and well maintained.
Immediately after World War I and during the 1920s,
city population growth was outpaced by population
growth in the suburbs by a factor of two. The focus at the
time was on the single-family suburban dwelling. The
1920s were a time of growth, but the decade following
the Great Depression, beginning in 1929, was one of
deflation, cessation of building, loss of mortgage financing, and the plunge into unemployment of large numbers
of building trade workers. Additionally, 1.5 million home
loans were foreclosed during this period. In 1936, the
housing market began to make a comeback; however, the
1930s would come to be known as the beginning of public housing, with increased public involvement in housing
construction, as demonstrated by the many laws passed
during the era [5]. The National Housing Act was passed
by Congress in 1934 and set up the Federal Housing
Administration. This agency encouraged banks, building
and loan associations, and others to make loans for building homes, small business establishments, and farm buildings. If the Federal Housing Administration approved the
plans, it would insure the loan. In 1937, Congress passed
another National Housing Act that enabled the Federal
Housing Administration to take control of slum clearance. It made 60-year loans at low interest to local governments to help them build apartment blocks. Rents in
these homes were fixed and were only available to lowincome families. By 1941, the agency had assisted in the
construction of more than 120,000 family units.
During World War II, the focus of home building was on
housing for workers who were involved in the war effort.
Homes were being built through federal agencies such as
the newly formed Federal Housing Administration,
formed in 1934 and transferred to HUD in 1965.
According to the U.S. Census Bureau (USCB) [7], in the
years since World War II, the types of homes Americans
live in have changed dramatically. In 1940, most homes
were considered attached houses (row houses, townhouses, and duplexes). Small apartment houses with two
Healthy Housing Reference Manual1-6 Chapter 1: Housing History and Purpose
to four apartments had their zenith in the 1950s. In the
1960 census, two-thirds of the housing inventory was
made up of one-family detached houses, which declined
to less than 60% in the 1990 census.
The postwar years saw the expansion of suburban housing led by William J. Levitt’s Levittown, on Long Island,
which had a strong influence on postwar building and
initiated the subdivisions and tract houses of the following decades (Figure 1.2). The 1950s and 1960s saw continued suburban development, with the growing ease of
transportation marked by the expansion of the interstate
highway system. As the cost of housing began to increase
as a result of increased demand, a grassroots movement to
provide adequate housing for the poor began to emerge.
According to Wright [5], in the 1970s only about 25% of
the population could afford a $35,000 home. According
to Gaillard [8], Koinonia Partners, a religious organization founded in 1942 by Clarence Jordan near Albany,
Georgia, was the seed for Habitat for Humanity. Habitat
for Humanity, founded in 1976 by Millard Fuller, is
known for its international efforts and has constructed
more than 150,000 houses in 80 countries; 50,000 of
these houses are in the United States. The homes are
energy-efficient and environmentally friendly to conserve
resources and reduce long-term costs to the homeowners.
Builders also began promoting one-floor minihomes and
no-frills homes of approximately 900 to 1,200 square
feet. Manufactured housing began to increase in popularity, with mobile home manufacturers becoming some of
the most profitable corporations in the United States in
the early 1970s. In the 1940 census, manufactured housing were lumped into the “other” category with boats and
tourist cabins: by the 1990 census, manufactured housing
made up 7% of the total housing inventory. Many communities ban manufactured housing from residential
neighborhoods.
According to Hart et al. [9], nearly 30% of all home sales
nationwide are of manufactured housing, and more than
90% of those homes are never moved once they are
anchored. According to a 2001 industry report, the
demand for prefabricated housing is expected to increase
in excess of 3% annually to $20 billion in 2005, with
most units being manufactured homes. The largest market is expected to continue in the southern part of the
United States, with the most rapid growth occurring in
the western part of the country. As of 2000, five manufactured-home producers, representing 35% of the market, dominated the industry. This industry, over the past
20 to 25 years, has been affected by two pieces of federal
legislation. The first, the Mobile Home Construction and
Safety Standards Act, adopted by HUD in 1974, was
passed to aid consumers through regulation and enforcement of HUD design and construction standards for
manufactured homes. The second, the 1980 Housing
Act, required the federal government to change the term
“mobile home” to “manufactured housing” in all federal
laws and literature. One of the prime reasons for this
change was that these homes were in reality no longer
mobile in the true sense.
The energy crisis in the United States between 1973 and
1974 had a major effect on the way Americans lived,
drove, and built their homes. The high cost of both heating and cooling homes required action, and some of the
action taken was ill advised or failed to consider healthy
housing concerns. Sealing homes and using untried insulation materials and other energy conservation actions
often resulted in major and sometimes dangerous buildups of indoor air pollutants. These buildups of toxins
occurred both in homes and offices. Sealing buildings for
energy efficiency and using off-gassing building materials
containing urea-formaldehyde, vinyl, and other new plastic surfaces, new glues, and even wallpapers created toxic
environments. These newly sealed environments were not
refreshed with makeup air and resulted in the accumulation of both chemical and biologic pollutants and moisture leading to mold growth, representing new threats to
both short-term and long-term health. The results of
these actions are still being dealt with today.
Figure 1.2. Levittown, New York
1-7Chapter 1: Housing History and PurposeHealthy Housing Reference Manual
References
1. Schoenauer N. 6,000 years of housing. New York/
London: W.W. Norton & Company, Inc.; 2000.
2. Chadwick E. Report on an enquiry into the sanitary
condition of the labouring population of Great Britain
and on the means of its improvements. London: Clowes
and Sons; 1842.
3. Shattuck L, Banks N Jr, Abbot J. Report of the Sanitary
Commission of Massachusetts, 1850. Boston: Dutton and
Wentworth; 1850. Available from URL: http://www.
deltaomega.org/shattuck.pdf.
4. Griscom JH. The sanitary condition of the labouring
population of New York. New York: Harper; 1845.
5. Wright G. Building the dream— a social history of
housing in America. Cambridge, MA/London: The MIT
Press; 1998.
6. Von Hoffman A. The origins of American housing
reform. Cambridge, MA: Joint Center for Housing
Studies— Harvard University; August 1998. p. W98-2.
7. US Census Bureau. Historical census of housing tables—
units in structure; 2002. Washington, DC: US Census
Bureau; 2002. Available from URL:
http://www.census.gov/hhes/www/housing/census/
historic/units.html.
8. Gaillard F. If I were a carpenter, twenty years of Habitat
for Humanity. Winston-Salem, NC: John E. Blair; 1996.
9. Hart JF, Rhodes MJ, Morgan JT, Lindberg MB. The
unknown world of the mobile home. Baltimore, MD:
Johns Hopkins University Press; 2002.
Additional Sources of Information
Dolkart A. The 1901 Tenement House Act: chapter 6,
cleaning up the toilets. New York: Lower East Side
Tenement Museum; no date. Available from URL:
http://www.tenement.org/ features_dolkart7.html.
Hale EE. Workingmen’s homes, essays and stories, on the
homes of men who work in large towns. Boston: James
R. Osgood and Company; 1874.
History of plumbing in America. Plumbing and
Mechanical Magazine. 1987 Jul. Available from URL:
http://www.plumbingsupply.com/pmamerica.html.
Housing Act of 1949, The US Committee on Agriculture
Glossary.
Lang RE, Sohmer RR. Editors’ introduction, legacy of
the Housing Act of 1949: the past, present, and future of
federal housing and urban policy. Housing Policy Debate
2000; 11(2) 291–8. Available from URL:
http://www.fanniemaefoundation.org/ programs/hpd/
v11i2-edintro.shtml.
Mason JB. History of housing in the US. 1930–1980.
Houston, TX: Gulf Publishing Company; 1982.
Passic F. Urban renewal. Morning Star [Albion,
Michigan]. 1997 Feb 13; 6. Available from URL:
http://www.albionmich.com/ history/histor_notebook/940213.shtml.
Red-lining [definition of ], 535A.1 Definitions, Iowa
Code 2001: Section 535A.1. Des Moines, IA: The Iowa
Legislature. Available from URL: http://www.legis.state.
ia.us/IACODE/ 2001/535A/1.html.
Rental Housing On Line. Federal housing acts. Port
Huron, MI: Rental Housing On Line; no date. Available
from URL: http://www.rhol.org/rental/fedact.htm.
Rental Housing On Line. Government’s role in low
income housing. Port Huron, MI: Rental Housing On
Line; no date. Available from URL: http://www.rhol.org/
rental/housing.htm.
Texas Low Income Housing Information Service. The
past: special interests, race, and local control; Housing
Act of 1949: bipartisan support for public housing.
Austin, TX: Texas Low Income Housing Information
Service; no date. Available from URL: http://www.texashousing.org/txlihis/ phdebate/past12.html.
US Department of Housing and Urban Development.
Fair housing laws and presidential Executive Orders.
Washington, DC: US Department of Housing and
Urban Development; no date. Available from URL:
http://www.hud.gov/ offices/ fheo/ FHLaws/index.cfm.
US Department of Housing and Urban Development.
Homes and communities. Washington, DC: US
Department of Housing and Urban Development; no
date. Available from URL: http://www.hud.gov.
Warth G. Research project looking at red-lining. North
County [California] Times 2002 May 5. Available from
URL: http://www.nctimes.com/ articles/2002/05/05/
export8963.txt.
Healthy Housing Reference Manual1-8 Chapter 1: Housing History and Purpose
2-1Chapter 2: Basic Principles of Healthy Housing Healthy Housing Reference Manual
Chapter 2: Basic Principles of Healthy Housing
“The connection between health and dwelling is one of the
most important that exists.”
Florence Nightingale
Introduction
It seems obvious that health is related to where people
live. People spend 50% or more of every day inside their
homes. Consequently, it makes sense that the housing
environment constitutes one of the major influences on
health and well-being. Many of the basic principles of the
link between housing and health were elucidated more
than 60 years ago by the American Public Health
Association (APHA) Committee on the Hygiene of
Housing. After World War II, political scientists, sociologists, and others became interested in the relation
between housing and health, mostly as an outgrowth of a
concern over poor housing conditions resulting from the
massive influx into American cities of veterans looking for
jobs. Now, at the beginning of the 21st century, there is a
growing awareness that health is linked not only to the
physical structure of a housing unit, but also to the
neighborhood and community in which the house is
located.
According to Ehlers and Steel [1], in 1938, a Committee
on the Hygiene of Housing, appointed by APHA, created
the Basic Principles of Healthful Housing, which provided guidance regarding the fundamental needs of
humans as they relate to housing. These fundamental
needs include physiologic and psychologic needs, protection against disease, protection against injury, protection
against fire and electrical shock, and protection against
toxic and explosive gases.
Fundamental Physiologic Needs
Housing should provide for the following physiologic
needs:
1. protection from the elements,
2. a thermal environment that will avoid undue heat loss,
3. a thermal environment that will permit adequate heat loss
from the body,
4. an atmosphere of reasonable chemical purity,
5. adequate daylight illumination and avoidance of undue
daylight glare,
6. direct sunlight,
7. adequate artificial illumination and avoidance of glare,
8. protection from excessive noise, and
9. adequate space for exercise and for children to play.
The first three physiologic needs reflect the requirement
for adequate protection from the elements. The lack of
adequate heating and cooling systems in homes can contribute to respiratory illnesses or even lead to death from
extreme temperatures. According to the National Weather
Service, 98 people died from extreme temperatures in
1996; 62 of these were due to extreme cold. Hypothermia
occurs when the body temperature drops below 96°F
(46°C). It can occur in any person exposed to severe cold
without enough protection. Older people are particularly
susceptible because they may not notice the cold as easily
and can develop hypothermia even after exposure to mild
cold. Susceptibility to the cold can be exacerbated by certain medications, medical conditions, or the consumption
of alcohol. Hyperthermia is the name given to a variety of
heat-related illnesses. The two most common forms of
hyperthermia are heat exhaustion and heat stroke. Of the
two, heat stroke is especially dangerous and requires
immediate medical attention.
According to the National Institute on Aging (NIA) [2],
lifestyle factors can increase the risk for hyperthermia:
Unbearably hot living quarters. This would include people who live in homes without fans or air conditioners. To
help avert the problem, residents should open windows at
night; create cross-ventilation by opening windows on two
sides of the building; cover windows when they are
exposed to direct sunlight and keep curtains, shades, or
blinds drawn during the hottest part of the day.
Lack of transportation. People without fans or air conditioners often are unable to go to shopping malls, movie
theaters, and libraries to cool off because of illness or the
lack of transportation.
Inadequate or inoperable windows. Society has become
so reliant on climate control systems that when they fail,
windows cannot be opened. As was the case in the 2003
heat wave in France, many homes worldwide do not even
have fans for cooling.
Overdressing. Older people, because they may not feel
the heat, may not dress appropriately in hot weather.
Healthy Housing Reference Manual2-2 Chapter 2: Basic Principles of Healthy Housing
Visiting overcrowded places. Trips should be scheduled
during nonrush-hour times and participation in special
events should be carefully planned to avoid disease
transmission.
Not checking weather conditions. Older people, particularly those at special risk, should stay indoors on especially hot and humid days, particularly when an air
pollution alert is in effect.
USCB [3] reported that about 75% of homes in the
United States used either utility gas or electricity for heating purposes, with utility gas accounting for about 50%.
This, of course, varies with the region of the country,
depending on the availability of hydroelectric power. This
compares with the 1940 census, which found that threequarters of all households heated with coal or wood.
Electric heat was so rare that it was not even an option on
the census form of 1940. Today, coal has virtually disappeared as a household fuel. Wood all but disappeared as a
heating fuel in 1970, but made a modest comeback at
4% nationally by 1990. This move over time to more
flexible fuels allows a majority of today’s homes to maintain healthy temperatures, although many houses still lack
adequate insulation.
The fifth through the seventh physiologic concerns
address adequate illumination, both natural and artificial.
Research has revealed a strong relationship between light
and human physiology. The effects of light on both the
human eye and human skin are notable. According to
Zilber [4], one of the physiologic responses of the skin to
sunlight is the production of vitamin D. Light allows us
to see. It also affects body rhythms and psychologic
health. Average individuals are affected daily by both natural and artificial lighting levels in their homes. Adequate
lighting is important in allowing people to see unsanitary
conditions and to prevent injury, thus contributing to a
healthier and safer environment. Improper indoor lighting can also contribute to eyestrain from inadequate illumination, glare, and flicker.
Avoiding excessive noise (eighth physiologic concern) is
important in the 21st century. However, the concept of
noise pollution is not new. Two thousand years ago, Julius
Caesar banned chariots from traveling the streets of Rome
late at night. In the 19th century, numerous towns and
cities prohibited ringing church bells. In the early 20th
century, London prohibited church bells from ringing
between 9:00 PM and 9:00 AM. In 1929, New York City
formed a Noise Abatement Commission that was charged
with evaluating noise issues and suggesting solutions. At
that time, it was concluded that loud noise affected
health and productivity. In 1930, this same commission
determined that constant exposure to loud noises could
affect worker efficiency and long-term hearing levels. In
1974, the U.S. Environmental Protection Agency (EPA)
produced a document titled Information on Levels of
Environmental Noise Requisite to Protect Public Health and
Welfare With an Adequate Margin of Safety [5]. This document identified maximum levels of 55 decibels outdoors
and 45 decibels indoors to prevent interference with
activities and 70 decibels for all areas to prevent hearing
loss. In 1990, the United Kingdom implemented The
Household Appliances (Noise Emission) Regulations [6]
to help control indoor noise from modern appliances.
Noise has physiologic impacts aside from the potential to
reduce hearing ability. According to the American
Speech-Language-Hearing Association [7], these effects
include elevated blood pressure; negative cardiovascular
effects; increased breathing rates, digestion, and stomach
disturbances; ulcers; negative effects on developing
fetuses; difficulty sleeping after the noise stops; plus the
intensification of the effects of drugs, alcohol, aging, and
carbon monoxide. In addition, noise can reduce attention
to tasks and impede speech communication. Finally, noise
can hamper performance of daily tasks, increase fatigue,
and cause irritability.
Household noise can be controlled in various ways.
Approaching the problem during initial construction is
the simplest, but has not become popular. For example,
in early 2003, only about 30% of homebuilders offered
sound-attenuating blankets for interior walls. A soundattenuating blanket is a lining of noise abatement products (the thickness depends on the material being used).
Spray-in-place soft foam insulation can also be used as a
sound dampener, as can special walking mats for floors.
Actions that can help reduce household noise include
installing new, quieter appliances and isolating washing
machines to reduce noise and water passing through
pipes.
The ninth and final physiologic need is for adequate
space for exercise and play. Before industrialization in the
United States and England, a preponderance of the population lived and worked in more rural areas with very
adequate areas for exercise and play. As industrialization
impacted demographics, more people were in cities without ample space for play and exercise. In the 19th century, society responded with the development of
playgrounds and public parks. Healthful housing should
include the provision of safe play and exercise areas.
2-3Chapter 2: Basic Principles of Healthy Housing Healthy Housing Reference Manual
Many American neighborhoods are severely deficient,
with no area for children to safely play. New residential
areas often do not have sidewalks or street lighting, nor
are essential services available by foot because of highway
and road configurations.
Fundamental Psychologic Needs
Seven fundamental psychologic needs for healthy housing
include the following:
1. adequate privacy for the individual,
2. opportunities for normal family life,
3. opportunities for normal community life,
4. facilities that make possible the performance of household
tasks without undue physical and mental fatigue,
5. facilities for maintenance of cleanliness of the dwelling and
of the person,
6. possibilities for aesthetic satisfaction in the home and its
surroundings, and
7. concordance with prevailing social standards of the local
community.
Privacy is a necessity to most people, to some degree and
during some periods. The increase in house size and the
diminishing family size have, in many instances, increased
the availability of privacy. Ideally, everyone would have
their own rooms, or, if that were not possible, would
share a bedroom with only one person of the same sex,
excepting married couples and small children.
Psychiatrists consider it important for children older than
2 years to have bedrooms separate from their parents. In
addition, bedrooms and bathrooms should be accessible
directly from halls or living rooms and not through other
bedrooms. In addition to the psychologic value of privacy, repeated studies have shown that lack of space and
quiet due to crowding can lead to poor school performance in children.
Coupled with a natural desire for privacy is the social
desire for normal family and community life. A wholesome atmosphere requires adequate living room space and
adequate space for withdrawal elsewhere during periods
of entertainment. This accessibility expands beyond the
walls of the home and includes easy communication with
centers of culture and business, such as schools, churches,
entertainment, shopping, libraries, and medical services.
Protection Against Disease
Eight ways to protect against contaminants include the
following:
1. provide a safe and sanitary water supply;
2. protect the water supply system against pollution;
3. provide toilet facilities that minimize the danger of
transmitting disease;
4. protect against sewage contamination of the interior
surfaces of the dwelling;
5. avoid unsanitary conditions near the dwelling;
6. exclude vermin from the dwelling, which may play a part
in transmitting disease;
7. provide facilities for keeping milk and food fresh; and
8. allow sufficient space in sleeping rooms to minimize the
danger of contact infection.
According to the U.S. EPA [8], there are approximately
160,000 public or community drinking water systems in
the United States. The current estimate is that 42 million
Americans (mostly in rural America) get their water from
private wells or other small, unregulated water systems.
The presence of adequate water, sewer, and plumbing
facilities is central to the prevention, reduction, and possible elimination of water-related diseases. According to
the Population Information Program [9], water-related
diseases can be organized into four categories:
• waterborne diseases, including those caused by both
fecal-oral organisms and those caused by toxic
substances;
• water-based diseases;
• water-related vector diseases; and
• water-scarce diseases.
Numerous studies link improvements in sanitation and
the provision of potable water with significant reductions
in morbidity and mortality from water-related diseases.
Clean water and sanitation facilities have proven to reduce
infant and child mortality by as much as 55% in Third
World countries according to studies from the 1980s.
Waterborne diseases are often referred to as “dirty-water”
diseases and are the result of contamination from chemical, human, and animal wastes. Specific diseases in this
group include cholera, typhoid, shigella, polio, meningitis, and hepatitis A and E. Water-based diseases are caused
by aquatic organisms that spend part of their life cycle in
the water and another part as parasites of animals.
Healthy Housing Reference Manual2-4 Chapter 2: Basic Principles of Healthy Housing
Although rare in the United States, these diseases include
dracunculiasis, paragonimiasis, clonorchiasis, and schistosomiasis. The reduction in these diseases in many countries has not only led to decreased rates of illness and
death, but has also increased productivity through a
reduction in days lost from work.
Water-related diseases are linked to vectors that breed and
live in or near polluted and unpolluted water. These vectors are primarily mosquitoes that infect people with the
disease agents for malaria, yellow fever, dengue fever, and
filariasis. While the control of vectorborne diseases is a
complex matter, in the United States, most of the control
focus has been on controlling habitat and breeding areas
for the vectors and reducing and controlling human cases
of the disease that can serve as hosts for the vector.
Vectorborne diseases have recently become a more of a
concern to the United States with the importation of the
West Nile virus. The transmission of West Nile virus
occurs when a mosquito vector takes a blood meal from a
bird or incidental hosts, such as a dog, cat, horse, or other
vertebrate. The human cases of West Nile virus in 2003
numbered 9,862, with 264 deaths. Finally, water-scarce
diseases are diseases that flourish where sanitation is poor
due to a scarcity of fresh water. Diseases included in this
category are diphtheria, leprosy, whooping cough, tetanus, tuberculosis, and trachoma. These diseases are often
transmitted when the supply of fresh water is inadequate
for hand washing and basic hygiene. These conditions are
still rampant in much of the world, but are essentially
absent from the United States due to the extensive availability of potable drinking water.
In 2000, USCB [10] reported that 1.4% of U.S. homes
lacked plumbing facilities. This differs greatly from the
1940 census, when nearly one-half of U.S. homes lacked
complete plumbing. The proportion has continually
dropped, falling to about one-third in 1950 and then to
one-sixth in 1960. Complete plumbing facilities are
defined as hot and cold piped water, a bathtub or shower,
and a flush toilet. The containment of household sewage
is instrumental in protecting the public from waterborne
and vectorborne diseases. The 1940 census revealed that
more than a third of U.S. homes had no flush toilet, with
70% of the homes in some states without a flush toilet.
Of the 13 million housing units at the time without flush
toilets, 11.8 million (90.7%) had an outside toilet or
privy, another 1 million (7.6%) had no toilet or privy,
and the remainder had a nonflush toilet in the structure.
In contrast to these figures, the 2000 census data demonstrate the great progress that has been made in providing
sanitary sewer facilities. Nationally, 74.8% of homes are
served by a public sewer, with 24.1% served by a septic
tank or cesspool, and the remaining 1.1% using other
means.
Vermin, such as rodents, have long been linked to property destruction and disease. Integrated pest management,
along with proper housing construction, has played a significant role in reducing vermin around the modern
home. Proper food storage, rat-proofing construction,
and ensuring good sanitation outside the home have
served to eliminate or reduce rodent problems in the 21st
century home.
Facilities to properly store milk and food have not only
been instrumental in reducing the incidence of some
foodborne diseases, but have also significantly changed
the diet in developed countries. Refrigeration can be
traced to the ancient Chinese, Hebrews, Greeks, and
Romans. In the last 150 years, great strides have been
made in using refrigeration to preserve and cool food.
Vapor compression using air and, subsequently, ammonia
as a coolant was first developed in the 1850s. In the early
1800s, natural ice was extracted for use as a coolant and
preserver of food. By the late 1870s, there were 35 commercial ice plants in the United States and, by 1909,
there were 2,000. However, as early as the 1890s, sources
of natural ice began to be a problem as a result of pollution and sewage dumped into bodies of water. Thus, the
use of natural ice as a refrigerant began to present a
health problem. Mechanical manufacture of ice provided
a temporary solution, which eventually resulted in providing mechanical refrigeration.
Refrigeration was first used by the brewing and meatpacking industries; but most households had iceboxes
(Figure 2.1), which made the ice wagon a popular icon of
the late 1800s and early 1900s. In 1915, the first refrigerator, the Guardian, was introduced. This unit was the
predecessor of the Frigidaire. The refrigerator became as
necessary to the household as a stove or sewing machine.
By 1937, nearly 6 million refrigerators were manufactured in the United States. By 1950, in excess of 80% of
American farms and more than 90% of urban homes had
a refrigerator.
Adequate living and sleeping space are also important in
protecting against contagion. It is an issue not only of
privacy but of adequate room to reduce the potential for
the transmission of contagion. Much improvement has
been made in the adequacy of living space for the U.S.
family over the last 30 years. According to USCB [11],
the average size of new single homes has increased from a
1970 average of 1,500 square feet to a 2000 average of
2-5Chapter 2: Basic Principles of Healthy Housing Healthy Housing Reference Manual
2,266 square feet. USCB [11] says that slightly less than
5% of U.S. homes were considered crowded in 1990;
that is, they had more than one person per room.
However, this is an increase since the 1980 census, when
the figure was 4.5%. This is the only time there has been
an increase since the first housing census was initiated in
1940, when one in five homes was crowded. During the
1940 census, most crowded homes were found in southern states, primarily in the rural south. Crowding has
become common in a few large urban areas, with more
than one-fourth of all crowded units located in four metropolitan areas: Houston, Los Angeles, Miami, and New
York. The rate for California has not changed significantly between 1940 (13%) and 1990 (12%). Excessive
crowding in homes has the potential to increase not only
communicable disease transmission, but also the stress
level of occupants because modern urban individuals
spend considerably more time indoors than did their
1940s counterparts.
Protection Against Injury
A major provision for safe housing construction is developing and implementing building codes. According to
the International Code Council one- and two-family
dwelling code, the purpose of building codes is to provide minimum standards for the protection of life, limb,
property, environment, and for the safety and welfare of
Figure 2.1. Circa 1890 Icebox
Source: Robert R. McCormick Museum, Wheaton, Illinois
the consumer, general public, and the owners and occupants of residential buildings regulated by this code [12].
However, as with all types of codes, the development of
innovative processes and products must be allowed to take
a place in improving construction technology. Thus,
according to the International Code Council one- and
two-family dwelling code, building codes are not intended
to limit the appropriate use of materials, appliances,
equipment, or methods by design or construction that are
not specifically prescribed by the code if the building official determines that the proposed alternate materials,
appliances, equipment or methods of design or construction are at least equivalent of that prescribed in this code.
While the details of what a code should include are
beyond the scope of this section, additional information
can be found at http://www.iccsafe.org/, the Web site of
the International Code Council (ICC). ICC is an organization formed by the consolidation of the Building
Officials and Code Administrators International,
Southern Building Code Congress International, Inc., and
the International Conference of Building Officials [12].
According to the Home Safety Council (HSC) [13], the
leading causes of home injury deaths in 1998 were falls
and poisonings, which accounted for 6,756 and 5,758
deaths, respectively. As expected, the rates and national
estimates of the number of fall deaths were highest among
those older than 64 years, and stairs or steps were associated with 17% of fall deaths. Overall, falls were the leading cause of nonfatal, unintentional injuries occurring at
home and accounted for 5.6 million injuries. Similar to
the mortality statistics, consumer products most often
associated with emergency department visits included
stairs and steps, accounting for 854,631 visits, and floors,
accounting for 556,800 visits. A national survey by HSC
found that one-third of all households with stairs did not
have banisters or handrails on at least one set of stairs.
Related to this, homes with older persons were more
likely to have banisters or handrails than were those where
young children live or visit. The survey also revealed that
48% of households have windows on the second floor or
above, but only 25% have window locks or bars to prevent children from falling out. Bathtub mats or nonskid
strips to reduce bathtub falls were used in 63% of
American households. However, in senior households (age
70 years and older), 79% used mats or nonskid strips.
Nineteen percent of the total number of homes surveyed
had grab bars to supplement the mats and strips.
Significantly, only 39% of the group most susceptible to
falls (people aged 70 years and older) used both nonskid
surfaces and grab bars.
Healthy Housing Reference Manual2-6 Chapter 2: Basic Principles of Healthy Housing
Protection Against Fire
An important component of safe housing is to control
conditions that promote the initiation and spread of fire.
Between 1992 and 2001, an average of 4,266 Americans
died annually in fires and nearly 25,000 were injured.
This fact and the following information from the United
States Fire Administration (USFA) [14] demonstrate the
impact that fire safety and the lack of it have in the
United States. The United States has one of the highest
fire death rates in the industrialized world, with 13.4
deaths per million people. At least 80% of all fire deaths
occur in residences. Residential fires account for 23% of
all fires and 76% of structure fires. In one- and two-family dwellings, fires start in the kitchen 25.5% of the time
and originate in the bedroom 13.7% of the time.
Apartment fires most often start in the kitchen, but at
almost twice the rate (48.5%), with bedrooms again
being the second most common place at 13.4%.
These USFA statistics also disclose that cooking is the
leading cause of home fires, usually a result of unattended
cooking and human error rather than mechanical failure
of the cooking units. The leading cause of fire deaths in
homes is careless smoking, which can be significantly
deterred by smoke alarms and smolder-resistant bedding
and upholstered furniture. Heating system fires tend to
be a larger problem in single-family homes than in apartments because the heating systems in family homes frequently are not professionally maintained.
A number of conditions in the household can contribute
to the creation or spread of fire. The USFA data indicate
that more than one-third of rural Americans use fireplaces, wood stoves, and other fuel-fired appliances as primary sources of heat. These same systems account for
36% of rural residential fires. Many of these fires are the
result of creosote buildup in chimneys and stovepipes.
These fires could be avoided by
• inspecting and cleaning by a certified chimney
specialist;
• clearing the area around the hearth of debris,
decorations, and flammable materials;
• using a metal mesh screen with fireplaces and leaving
glass doors open while burning a fire;
• installing stovepipe thermometers to monitor flue
temperatures;
• leaving air inlets on wood stoves open and never
restricting air supply to the fireplaces, thus helping to
reduce creosote buildup;
• using fire-resistant materials on walls around wood
stoves;
• never using flammable liquids to start a fire;
• using only seasoned hardwood rather than soft, moist
wood, which accelerates creosote buildup;
• building small fires that burn completely and produce
less smoke;
• never burning trash, debris, or pasteboard in a fireplace;
• placing logs in the rear of the fireplace on an adequate
supporting grate;
• never leaving a fire in the fireplace unattended;
• keeping the roof clear of leaves, pine needles, and other
debris;
• covering the chimney with a mesh screen spark arrester;
and
• removing branches hanging above the chimney, flues,
or vents.
USFA [14] also notes that manufactured homes can be
susceptible to fires. More than one-fifth of residential fires
in these facilities are related to the use of supplemental
room heaters, such as wood- and coal-burning stoves,
kerosene heaters, gas space-heaters, and electrical heaters.
Most fires related to supplemental heating equipment
result from improper installation, maintenance, or use of
the appliance. USFA recommendations to reduce the
chance of fire with these types of appliances include the
following:
• placing wood stoves on noncombustible surfaces or a
code-specified or listed floor surface;
• placing noncombustible materials around the opening
and hearth of fireplaces;
• placing space heaters on firm, out-of-the-way surfaces
to reduce tipping over and subsequent spillage of fuel
and providing at least 3 feet of air space between the
heating device and walls, chairs, firewood, and curtains;
• placing vents and chimneys to allow 18 inches of air
space between single-wall connector pipes and
combustibles and 2 inches between insulated chimneys
and combustibles; and
• using only the fuel designated by the manufacturer for
the appliance.
The ability to escape from a building when fire has been
discovered or detected is of extreme importance. In the
2-7Chapter 2: Basic Principles of Healthy Housing Healthy Housing Reference Manual
modern home, three key elements can contribute to a safe
exit from a home during the threat of fire. The first of
these is a working smoke alarm system. The average
homeowner in the 1960s had never heard of a smoke
alarm, but by the mid-1980s, laws in 38 states and in
thousands of municipalities required smoke alarms in all
new and existing residences. By 1995, 93% of all singlefamily and multifamily homes, apartments, nursing
homes, and dormitories were equipped with alarms. The
cost decreased from $1,000 for a professionally installed
unit for a three-bedroom home in the 1970s to an ownerinstalled $10 unit. According to the EPA [15], ionization
chamber and photoelectric are the two most common
smoke detectors available commercially. Helmenstein [16]
states that a smoke alarm uses one or both methods, and
occasionally uses a heat detector, to warn of a fire. These
units can be powered by a 9-volt battery, a lithium battery, or 120-volt house wiring. Ionization detectors function using an ionization chamber and a minute source of
ionizing radiation. The radiation source is americium-241
(perhaps 1/5,000th of a gram), while the ionization
chamber consists of two plates separated by about a centimeter. The power source (battery or house current)
applies voltage to the plates, resulting in one plate being
charged positively while the other plate is charged negatively. The americium constantly releases alpha particles
that knock electrons off the atoms in the air, ionizing the
oxygen and nitrogen atoms in the chamber. The negative
plate attracts the positively charged oxygen and nitrogen
atoms, while the electrons are attracted to the positive
plate, generating a small, continuous electric current. If
smoke enters the ionization chamber, the smoke particles
attach to the ions and neutralize them, so they do not
reach the plate. The alarm is then triggered by the drop
in current between the plates [16].
Photoelectric devices function in one of two ways. First,
smoke blocks a light beam, reducing the light reaching
the photocell, which sets off the alarm. In the second and
more common type of photoelectric unit, smoke particles
scatter the light onto a photocell, initiating an alarm.
Both detector types are effective smoke sensors and both
must pass the same test to be certified as Underwriters
Laboratories (UL) smoke detectors. Ionization detectors
respond more quickly to flaming fires with smaller combustion particles, while photoelectric detectors respond
more quickly to smoldering fires. Detectors can be damaged by steam or high temperatures. Photoelectric detectors are more expensive than ionization detectors and are
more sensitive to minute smoke particles. However, ionization detectors have a degree of built-in security not
inherent to photoelectric detectors. When the battery
starts to fail in an ionization detector, the ion current falls
and the alarm sounds, warning that it is time to change
the battery before the detector becomes ineffective.
Backup batteries may be used for photoelectric detectors
that are operated using the home’s electrical system.
According to USFA [14], a properly functioning smoke
alarm diminishes the risk for dying in a fire by approximately 50% and is considered the single most important
means of preventing house and apartment fire fatalities.
Proper installation and maintenance, however, are key to
their usefulness. Figure 2.2 shows a typical smoke alarm
being tested.
Following are key issues regarding installation and maintenance of smoke alarms. (Smoke alarms should be
installed on every level of the home including the basement, both inside and outside the sleeping area.)
• Smoke alarms should be installed on the ceiling or
6–8 inches below the ceiling on side walls.
• Battery replacement is imperative to ensuring proper
operation. Typically, batteries should be replaced at
least once a year, although some units are
manufactured with a 10-year battery. A “chirping”
noise from the unit indicates the need for battery
replacement. A battery-operated smoke alarm has a life
expectancy of 8 to 10 years.
• Battery replacement is not necessary in units that are
connected to the household electrical system.
• Regardless of the type, it is crucial to test every smoke
alarm monthly. Data from HSC [13] revealed that
only 83% of individuals with fire alarms test them at
least once a year; while only 19% of households with
at least one smoke alarm test them quarterly.
A second element impacting escape from a building is a
properly installed fire-suppression system. According to
USFA [14], sprinkler systems began to be used over 100
years ago in New England textile mills. Currently, few
homes are protected by residential sprinkler systems.
However, UL-listed home systems are available and are
designed to protect homes much faster than standard
commercial or industrial sprinklers. Based on approximately 1% of the total building price in new construction, sprinkler systems can be installed for a reasonable
price. These systems can be retrofitted to existing construction and are smaller than commercial systems. In
addition, homeowner insurance discounts for such systems range between 5% and 15% and are increasing in
availability.
Healthy Housing Reference Manual2-8 Chapter 2: Basic Principles of Healthy Housing
The final element in escaping from a residential fire is
having a fire plan. A 1999 survey conducted by USFA
[14] found that 60% of Americans have an escape plan,
with 42% of these individuals having practiced the plan.
Surprisingly, 26% of Americans stated they had never
thought about practicing an escape plan, and 3% believed
escape planning to be unnecessary. In addition, of the
people who had a smoke alarm sound an alert over the
past year before the study, only 8% believed it to be a fire
and thought they should evacuate the building.
Protection from electrical shocks and burns is also a vital
element in the overall safety of the home. According to
the National Fire Protection Association (NFPA) [17],
electrical distribution equipment was the third-leading
cause of home fires and the second-leading cause of fire
deaths in the United States between 1994 and 1998.
Specifically, NFPA reported that 38,300 home electrical
fires occurred in 1998, which resulted in 284 deaths,
1,184 injuries, and approximately $670 million in direct
property damage. The same report indicated that the
leading cause of electrical distribution fires was ground
fault or short-circuit problems. A third of the home electrical distribution fires were a result of problems with
fixed wiring, while cords and plugs were responsible for
17% of these fires and 28% of the deaths.
Additional investigation of these statistics reveals that
electrical fires are one of the leading types of home fires
in manufactured homes. USFA [14] data demonstrate
that many electrical fires in homes are associated with
improper installation of electrical devices by do-it-yourFigure 2.2. Smoke Alarm Testing
Source: Federal Emergency Management Agency
selfers. Errors attributed to this amateur electrical work
include use of improperly rated devices such as switches
or receptacles and loose connections leading to overheating and arcing, resulting in fires. Recommendations to
reduce the risk of electrical fires and electrocution include
the following:
1. Use only the correct fuse size and do not use pennies
behind a fuse.
2. Install ground fault circuit interrupters (GFCI) on all
outlets in kitchens, bathrooms, and anywhere else near
water. This can also be accomplished by installing a GFCI
in the breaker box, thus protecting an entire circuit.
3. Never place combustible materials near light fixtures,
especially halogen bulbs that get very hot.
4. Use only the correct bulb size in a light fixture.
5. Use only properly rated extension cords for the job
needed.
6. Never use extension cords as a long-term solution to the
need for an additional outlet. Size the extension cord to
the wattage to be used.
7. Never run extension cords inside walls or under rugs
because they generate heat that must be able to dissipate.
Fire Extinguishers
A fire extinguisher should be listed and labeled by an
independent testing laboratory such as FM (Factory
Mutual) or UL. Fire extinguishers are labeled according
to the type of fire on which they may be used. Fires
involving wood or cloth, flammable liquids, electrical, or
metal sources react differently to extinguishers. Using the
wrong type of extinguisher on a fire could be dangerous
and could worsen the fire. Traditionally, the labels A, B,
C, and D have been used to indicate the type of fire on
which an extinguisher is to be used.
Type A— Used for ordinary combustibles such as cloth,
wood, rubber, and many plastics. These types of fire usually leave ashes after they burn: Type A extinguishers for
ashes. The Type A label is in a triangle on the
extinguisher.
Type B— Used for flammable liquid fires such as oil, gasoline, paints, lacquers, grease, and solvents. These substances often come in barrels: Type B extinguishers for
barrels. The Type B label is in a square on the
extinguisher.
Type C— Used for electrical fires such as in wiring, fuse
boxes, energized electrical equipment, and other electrical
2-9Chapter 2: Basic Principles of Healthy Housing Healthy Housing Reference Manual
sources. Electricity travels in currents; Type C extinguishers for currents. The Type C label is in a circle on the
extinguisher.
Type D— Used for metal fires such as magnesium, titanium, and sodium. These types of fires are very dangerous and seldom handled by the general public; Type D
means don’t get involved. The Type D label is in a star on
the extinguisher.
The higher the rating number on an A or B fire extinguisher, the more fire it can put out, but high-rated units
are often the heavier models. Extinguishers need care and
must be recharged after every use— a partially used unit
might as well be empty. An extinguisher should be placed
in the kitchen and in the garage or workshop. Each extinguisher should be installed in plain view near an escape
route and away from potential fire hazards such as heating appliances.
Recently, pictograms have come into use on fire extinguishers. These picture the type of fire on which an extinguisher is to be used. For instance, a Type A extinguisher
has a pictogram showing burning wood. A Type C extinguisher has a pictogram showing an electrical cord and
outlet. These pictograms are also used to show what not
to use. For example, a Type A extinguisher also show a
pictogram of an electrical cord and outlet with a slash
through it (do not use it on an electrical fire).
Fire extinguishers also have a number rating. For Type A
fires, 1 means 1¼ gallons of water; 2 means 2½ gallons of
water, 3 means 3¾ gallons of water, etc. For Type B and
Type C fires, the number represents square feet. For example, 2 equals 2 square feet, 5 equals 5 square feet, etc.
Fire extinguishers can also be made to extinguish more
than one type of fire. For example, you might have an
extinguisher with a label that reads 2A5B. This would
mean this extinguisher is good for Type A fires with a
2½-gallon equivalence and it is also good for Type B fires
with a 5-square-foot equivalency. A good extinguisher to
have in each residential kitchen is a 2A10BC fire extinguisher. You might also get a Type A for the living room
and bedrooms and an ABC for the basement and garage.
PASS is a simple acronym to remind you how to operate
most fire extinguishers— pull, aim, squeeze, and sweep.
Pull the pin at the top of the cylinder. Some units require
the releasing of a lock latch or pressing a puncture lever.
Aim the nozzle at the base of the fire. Squeeze or press
the handle. Sweep the contents from side to side at the
base of the fire until it goes out. Shut off the extinguisher
and then watch carefully for any rekindling of the fire.
Protection Against Toxic Gases
Protection against gas poisoning has been a problem since
the use of fossil fuels was combined with relatively tight
housing construction. NFPA [17] notes that National
Safety Council statistics reflect unintentional poisonings
by gas or vapors, chiefly carbon monoxide (CO), numbering about 600 in 1998. One-fourth of these involved
heating or cooking equipment in the home. The U.S.
Consumer Product Safety Commission [18] states that in
2001 an estimated 130 deaths occurred as a result of CO
poisoning from residential sources; this decrease in deaths
is related to the increased use of CO detectors. In addition, approximately 10,000 cases of CO-related injuries
occur each year. NFPA [17] also notes that, similar to fire
deaths, unintentional CO deaths are highest for ages 4
years and under and ages 75 years and older. Additional
information about home CO monitoring can be found in
Chapter 5.
References
1. Ehlers VE, Steel EW. Municipal and rural sanitation. Sixth
edition. New York: McGraw-Hill Book Company; 1965.
p. 462–4.
2. National Institute on Aging. Hyperthermia— too hot for
your health, fact sheet health information. Bethesda, MD:
US Department of Health and Human Services; no date.
Available from URL: http://www.niapublications.org/
engagepages/ hyperther.asp.
3. US Census Bureau. Historical census of housing tables—
house heating fuel. Washington, DC: US Census Bureau;
2002. Available from URL: http://www.census.gov/hhes/
www/housing/census/historic/fuels.html.
4. Zilber SA. Review of health effects of indoor lighting.
Architronic 1993;2(3). Available from URL:
http://architronic.saed.kent.edu/v2n3/v2n3.06.html.
5. US Environmental Protection Agency. Information on
levels of environmental noise requisite to protect public
health and welfare with an adequate margin of safety.
Washington, DC: US Environmental Protection Agency;
1974.
6. Public Health, England and Wales. The Household
Appliances (Noise Emission) Regulations 1990. London:
Her Majesty’s Stationery Office; 1990.
7. American Speech-Language-Hearing-Association. Noise:
noise is difficult to define. Rockville, MD: American
Speech-Language-Hearing-Association; 2003. Available
from URL: http://www.asha.org/public/hearing/disorders/
noise.htm.
Healthy Housing Reference Manual2-10 Chapter 2: Basic Principles of Healthy Housing
8. US Environmental Protection Agency. Factoids: drinking
water and ground water statistics for 2002. Washington,
DC: US Environmental Protection Agency, Office of
Ground Water and Drinking Water; January 2003.
Available from URL: http://www.epa.gov/safewater.
9. Hinrichsen D, Robey B, Upadhyay UD. The health
dimension. In: Solutions for a water-short world.
Population Report, Series M, No. 14. Baltimore, MD:
Johns Hopkins School of Public Health, Population
Information Program; 1998. Available from URL:
http://www.infoforhealth.org/pr/m14/m14chap5.shtml
10. US Census Bureau. Historical census of housing tables—
plumbing facilities, 2002. Washington, DC: US Census
Bureau; 2003. Available from URL: http://www.census.
gov/hhes/www/housing/census/historic/plumbing.html.
11. US Census Bureau. Historical census of housing tables—
crowded and severely crowded housing units, 2002.
Washington, DC: US Census Bureau; 2003. Available
from URL: http://www.census.gov/hhes/www/housing/
census/historic/crowding.html.
12. International Code Council. Fact sheet. Falls Church, VA:
International Code Council; no date. Available from
URL: http://www.iccsafe.org/news/pdf/factssheet.pdf.
13. Home Safety Council. The state of home safety in
America— executive summary. Washington, DC: The
Home Safety Council; 2002.
14. US Fire Administration. Welcome to the U.S. Fire
Administration (USFA) Web site. Washington, DC:
Federal Emergency Management Agency, Department
of Homeland Security; 2003. Available from URL:
http://www.usfa.fema.gov/.
15. US Environmental Protection Agency. Smoke detectors
and radiation. Washington, DC: US Environmental
Protection Agency; 2003. Available from URL:
http://www.epa.gov/ radiation/sources/smoke_alarm.htm.
16. Helmenstein AM. How do smoke detectors work?
Photoelectric & ionization smoke detectors, what you
need to know about chemistry. New York: About,
Inc.; 2003. Available from URL: http://chemistry.about.
com/library/weekly/aa071401a.htm.
17. National Fire Protection Association. NFPA fact sheets—
electrical safety. Quincy, MA: National Fire Protection
Association; 2003. Available from URL: http://www.nfpa.
org/Research/NFPAFactSheets/Electrical/electrical.asp.
18. US Consumer Product Safety Commission. Nonfire
carbon monoxide deaths: 2001 annual estimate.
Washington, DC: US Consumer Product Safety
Commission; 2004. Available from URL:
http://www.cpsc.gov/LIBRARY/co04.pdf.
Additional Sources of Information
Barbalace RC. Environmental justice and the NIMBY
principle. Environmental Chemistry.com: Environmental,
Chemistry, and Hazardous Materials Information and
Resources. Portland, ME; no date. Available from URL:
http://environmentalchemistry.com/yogi/hazmat/
articles/nimby.html.
Bryant B. The role of SNRE in the environmental justice
movement. Ann Arbor, MI: University of Michigan;
1997. Available from URL: http://www.umich.
edu/~snre492/ history.html.
Bullard RD. Waste and racism: a stacked deck? Forum
Appl Res Public Pol spring 1993.
National Institute on Aging. Hypothermia: a cold
weather hazard, fact sheet health information. Bethesda,
MD: US Department of Health and Human Services;
2001. Available from URL: http://www.niapublications.
org/engagepages/hypother.asp.
National Weather Service. Natural hazard statistics; no
date. Silver Spring, MD: National Weather Service.
Available from URL: http://www.nws.noaa.gov/om/hazstats.shtml.
US Census Bureau. New residential construction (building permits, housing starts, and housing completions).
Washington, DC: US Census Bureau; no date. Available
from URL: http://www.census.gov/newresconst.
3-1Chapter 3: Housing RegulationsHealthy Housing Reference Manual
“The poorest man may in his cottage bid defiance to all the
force of the Crown. It may be frail— its roof may shake—
the wind may blow through it— the storm may enter, the
rain may enter— but the King of England cannot enter—
all his force dares not cross the threshold of the ruined
tenement!”
William Pitt, March 1763
Introduction
William Pitt, arguing before the British Parliament
against excise officers entering private homes to levy the
Cyder Tax, eloquently articulated this long-held and cherished notion of the sanctity of private property. However,
a person’s right to privacy is not absolute. There has
always been a tension between the rights of property owners to do whatever they desire with their property and the
ability of the government to regulate uses to protect the
safety, health, and welfare of the community. Few, however, would argue with the right and duty of a city government to prohibit the operation of a munitions factory
or a chemical plant in the middle of a crowded residential
neighborhood.
History
The first known housing laws are in the Code of Laws of
Hammurabi [1], who was the King of Babylonia, circa
1792–1750 BC. These laws addressed the responsibility
of the home builder to construct a quality home and outlined the implications to the builder if injury or harm
came to the owner as a result of the failure to do so.
During the Puritan period (about 1620–1690), housing
laws essentially governed the behavior of the members of
the society. For example, no one was allowed to live
alone, so bachelors, widows, and widowers were placed
with other families as servants or boarders. In 1652,
Boston prohibited building privies within 12 feet of the
street. Around the turn of the 18th century, some New
England communities implemented local ordinances that
specified the size of houses. During the 17th century,
additional public policies on housing were established.
Because the English tradition of using wooden chimneys
and thatched roofs led to fires in many dwellings, several
colonies passed regulations prohibiting them.
After the early 17th century came an era of very rapid
metropolitan growth along the East Coast. This growth
was due largely to immigration from Europe and was
spurred by the Industrial Revolution. The most serious
Chapter 3: Housing Regulations
housing problems began in New York about 1840 when
the first tenements were built. In 1867, a report by the
New York Metropolitan Board of Health on living conditions in tenements convinced the New York State legislature to pass the Tenement Housing Act of 1867 [2]. The
principal requirements of the act included the following:
• Every room occupied for sleeping, if it does not
communicate directly with the external air, must have
a ventilating or transom window of at least 3 square
feet to the neighboring room or hall.
• A proper fire escape is necessary on every tenement or
lodging house.
• The roof is to be kept in repair and the stairs are to
have banisters.
• At least one toilet is required for every 20 occupants
for all such houses, and those toilets must be
connected to approved disposal systems.
• Cleansing of every lodging house is to be to the
satisfaction of the Board of Health, which is to have
access at any time.
• All cases of infectious disease are to be reported to the
Board by the owner or his agent; buildings are to be
inspected and, if necessary, disinfected or vacated if
found to be out of repair.
There were also regulations governing distances between
buildings, heights of rooms, and dimensions of windows.
Although this act had some beneficial influences on overcrowding, sewage disposal, lighting, and ventilation, perhaps its greatest contribution was in laying a foundation
for more stringent future legislation.
Jacob A. Riis, a Danish immigrant and a police reporter
on New York’s Lower East Side, published a book titled
How the Other Half Lives— Studies Among the Tenements
of New York [3], which swayed public opinion in the
direction of housing reform and resulted in the Tenement
House Act of 1901. The basic principles established in
the Tenement House Act of 1901 still underlie much of
the housing efforts in New York City today [4]. Since
1909, with the establishment of the Philadelphia
Housing Association, that city has had almost continual
inspection and improvement. Chicago enacted housing
legislation as early as 1889 and health legislation as early
as 1881. Regulations on ventilation, light, drainage, and
plumbing were put into effect in 1896.
Healthy Housing Reference Manual3-2 Chapter 3: Housing Regulations
Before 1892, all government involvement in housing was
at a local level. In 1892, however, the federal government
passed a resolution authorizing investigation of slum conditions in cities with 200,000 or more inhabitants.
Congress appropriated only $20,000 (roughly equal to
$390,000 in 2003) to cover the expenses of this project,
which limited the number of investigations.
No significant housing legislation was passed in the 20th
century until 1929 [5], when the New York State legislature passed its Multiple Dwelling Law. Other cities and
states followed New York’s example and permitted less
strict requirements in their codes. This decreased what
little emphasis there was on enforcement. Conditions
declined until, by the 1930s, President Franklin D.
Roosevelt’s shocking report to the people was “that onethird of the nation is ill-fed, ill-housed, and ill-clothed.”
In response to the overwhelming loss of homes during
the Great Depression, Congress passed the United States
Housing Act of 1937, which created the United States
Housing Authority (USHA). This act subsidized construction of new public housing units and required the
elimination of at least an equivalent number of units
from the local housing supply that were determined to be
inferior. In 1942, the USHA was renamed the Federal
Public Housing Administration and, in 1947, was
renamed the Public Housing Administration.
The federal government not only encouraged the construction of public housing, but took on the role of
financing private housing. In 1938, the Federal National
Mortgage Association was created. (Fannie Mae became a
private organization in 1968 [6].) Its purpose was to provide a secondary market for the FHA, created in 1934,
and Veterans Administration (VA) mortgage loans. The
Servicemen’s Readjustment Act of 1944, also known as
the GI Bill of Rights, created a VA loan program guaranteeing home mortgage loans for veterans. This legislation,
in conjunction with the FHA loan program, was the
impetus for initiating the huge program of home construction and subsequent suburban growth following
World War II. In 1946, the Farmers Home
Administration, housed in the United States Department
of Agriculture (USDA), was created to make loans and
grants for constructing and repairing farm homes and
assisting rural self-help housing groups.
The Housing Act of 1949 allowed “primarily residential”
and “blighted” urban areas to be condemned, cleared of
buildings, and sold for private development. In addition
to assisting in slum clearance, this act also provided for
additional public housing and authorized the USDA to
provide farmers with loans to construct, improve, repair
or replace dwellings to provide decent, safe, and sanitary
living conditions for themselves, their tenants, lessees,
sharecroppers, and laborers.
Because the many housing responsibilities administered
by various agencies within the federal government proved
unwieldy, the Housing and Urban Development Act was
passed in 1965. The U.S. Department of Housing and
Urban Development (HUD) was created to centralize the
responsibilities of the Housing and Home Finance
Agency and incorporated the FHA, the Federal National
Mortgage Association, the Public Housing
Administration, Urban Development Administration, and
the Community Facilities Administration.
Zoning, Housing Codes, and Building Codes
Housing is inextricably linked to the land on which it is
located. Changes in the patterns of land use in the United
States, shifting demographics, an awareness of the need
for environmental stewardship, and competing uses for
increasingly scarce (desirable) land have all placed added
stress on the traditional relationship between the property
owner and the community. This is certainly not a new
development.
In the early settlement of this country, following the precedent set by their forefathers from Great Britain, gunpowder mills and storehouses were prohibited from the
heavily populated portions of towns, owing to the frequent fires and explosions. Later, zoning took the form of
fire districts and, under implied legislative powers,
wooden buildings were prohibited from certain sections
of a municipality. Massachusetts passed one of the first
zoning laws in 1692. This law authorized Boston, Salem,
Charlestown, and certain other market towns in the province to restrict the establishment of slaughterhouses and
stillhouses for currying leather to certain locations in each
town.
Few people objected to such restrictions. Still, the tension
remained between the right to use one’s land and the
community’s right to protect its citizens. In 1926, the
United States Supreme Court took up the issue in Village
of Euclid, Ohio, v. Ambler Realty [7]. In this decision,
the Court noted,
“Until recent years, urban life was
comparatively simple; but with great increase
and concentration of population, problems have
developed which require additional restrictions
in respect of the use and occupation of private
lands in urban communities.”
3-3Chapter 3: Housing RegulationsHealthy Housing Reference Manual
In explaining its reasoning, the Court said,
“the law of nuisances may be consulted not
for the purpose of controlling, but for the
helpful aid of its analogies in the process of
ascertaining the scope of the police power.
Thus the question of whether the power
exists to forbid the erection of a building of a
particular kind or a particular use is to be
determined, not by an abstract consideration
of the building or other thing considered
apart, but by considering it in connection
with the circumstances and the locality…
A nuisance may be merely the right thing in
the wrong place— like a pig in the parlor
instead of the barnyard.”
Zoning, housing, and building codes were adopted to
improve the health and safety of people living in communities. And, to some extent, they have performed this function. Certainly, housing and building codes, when
enforced, have resulted in better constructed and maintained buildings. Zoning codes have been effective in segregating noxious and dangerous enterprises from residential
areas. However, as the U.S. population has grown and
changed from a rural to an urban then to a suburban society, land use and building regulations developed for the
19th and early 20th centuries are creating new health and
safety problems not envisioned in earlier times.
Zoning and Zoning Ordinances
Zoning is essentially a means of ensuring that a community’s land uses are compatible with the health, safety, and
general welfare of the community. Experience has shown
that some types of controls are needed to provide orderly
growth in relation to the community plan for development. Just as a capital improvement program governs
public improvements such as streets, parks and other recreational facilities, schools, and public buildings, so zoning governs the planning program with respect to the use
of public and private property.
It is very important that housing inspectors know the
general nature of zoning regulations because properties in
violation of both the housing code and the zoning ordinance must be brought into full compliance with the
zoning ordinance before the housing code can be
enforced. In many cases, the housing inspector may be
able to eliminate violations or properties in violation of
housing codes through enforcement of the zoning
ordinance.
Zoning Objectives
As stated earlier, the purpose of a zoning ordinance is to
ensure that the land uses within a community are regulated not only for the health, safety, and welfare of the
community, but also are in keeping with the comprehensive plan for community development. The provisions in
a zoning ordinance that help to achieve development that
provides for health, safety, and welfare are designed to do
the following:
• Regulate height, bulk, and area of structure. To
provide established standards for healthful housing
within the community, regulations dealing with
building heights, lot coverage, and floor areas must be
established. These regulations then ensure that
adequate natural lighting, ventilation, privacy, and
recreational areas for children will be realized. These
are all fundamental physiologic needs necessary for a
healthful environment. Safety from fires is enhanced
by separating buildings to meet yard and open-space
requirements. Through requiring a minimum lot area
per dwelling unit, population density controls are
established.
• Avoid undue levels of noise, vibration, glare, air
pollution, and odor. By providing land-use category
districts, these environmental stresses upon the
individual can be reduced.
• Lessen street congestion by requiring off-street parking
and off-street loading.
• Facilitate adequate provision of water, sewerage,
schools, parks, and playgrounds.
• Provide safety from flooding.
• Conserve property values. Through careful
enforcement of the zoning ordinance provisions,
property values can be stabilized and conserved.
To understand more fully the difference between zoning
and subdivision regulations, building codes, and housing
ordinances, the housing inspector must know what cannot be accomplished by a zoning ordinance. Items that
cannot be accomplished by a zoning ordinance include
the following:
• Overcrowding or substandard housing. Zoning is not
retroactive and cannot correct existing conditions.
These are corrected through enforcement of a
minimum standards housing code.
• Materials and methods of construction. Materials and
methods of construction are enforced through
building codes rather than through zoning.
Healthy Housing Reference Manual3-4 Chapter 3: Housing Regulations
• Cost of construction. Quality of construction, and
hence construction costs, are often regulated through
deed restrictions or covenants. Zoning does, however,
stabilize property values in an area by prohibiting
incompatible development, such as heavy industry in
the midst of a well-established subdivision.
• Subdivision design and layout. Design and layout of
subdivisions, as well as provisions for parks and streets,
are controlled through subdivision regulations.
Content of the Zoning Ordinance
Zoning ordinances establish districts of whatever size,
shape, and number the municipality deems best for carrying out the purposes of the zoning ordinance. Most cities
use three major districts: residential (R), commercial (C),
and industrial (I). These three may then be subdivided
into many subdistricts, depending on local conditions;
e.g., R-1 (single-unit dwellings), R-2 (duplexes), R-3
(low-rise apartment buildings), and so on. These districts
specify the principal and accessory uses, exceptions, and
prohibitions [8].
In general, permitted land uses are based on the intensity
of land use— a less intense land use being permitted in a
more intense district, but not vice versa. For example, a
single-unit residence is a less intense land use than a multiunit dwelling (defined by HUD as more than four living units) and hence would be permitted in a residential
district zoned for more intense land use (e.g., R-3). A
multiunit dwelling would not, however, be permitted in
an R-1 district. While intended to promote the health,
safety, and general welfare of the community, housing
trends in the last half of the 20th century have led a
number of public health and planning officials to question the blind enforcement of zoning districts. These
individuals, citing such problems as urban sprawl, have
stated that municipalities need to adopt a more flexible
approach to land use regulation— one that encourages
creating mixed-use spaces, increasing population densities, and reducing reliance on the automobile.
These initiatives are often called smart growth programs.
It is imperative, if this approach is taken, that both governmental officials and citizens be involved in the planning stage. Without this involvement, the community
may end up with major problems, such as overloaded
infrastructure, structures of inappropriate construction
crowded together, and fire and security issues for residents. Increased density could strain the existing water,
sewer and waste collection systems, as well as fire and
police services, unless proper planning is implemented.
In recent years, some ordinances have been partially based
on performance standards rather than solely on land-use
intensity. For example, some types of industrial developments may be permitted in a less intense use district provided that the proposed land use creates no noise, glare,
smoke, dust, vibration, or other environmental stress
exceeding acceptable standards and provided further that
adequate off-street parking, screening, landscaping, and
similar measures are taken.
Bulk and Height Requirements. Most early zoning ordinances stated that, within a particular district, the height
and bulk of any structure could not exceed certain
dimensions and specified dimensions for front, side, and
rear yards. Another approach was to use floor-area ratios
for regulation. A floor-area ratio is the relation between
the floor space of the structure and the size of the lot on
which it is located. For example, a floor-area ratio of 1
would permit either a two-story building covering 50%
of the lot, or a one-story building covering 100% of the
lot, as demonstrated in Figure 3.1. Other zoning ordinances specify the maximum amount of the lot that can
be covered or merely require that a certain amount of
open space must be provided for each structure, and leave
the builder the flexibility to determine the location of the
structure. Still other ordinances, rather than specify a particular height for the structure, specify the angle of light
obstruction that will assure adequate air and light to the
surrounding structures, as demonstrated in Figure 3.2.
Yard Requirements. Zoning ordinances also contain
minimum requirements for front, rear, and side yards.
These requirements, in addition to stating the lot dimensions, usually designate the amount of setback required.
Most ordinances permit the erection of auxiliary buildings in rear yards provided that they are located at stated
distances from all lot lines and provided sufficient open
space is maintained. If the property is a corner lot, additional requirements are established to allow visibility for
motorists.
Off-street Parking. Space for off-street parking and offstreet loading, especially for commercial buildings, is also
contained in zoning ordinances. These requirements are
based on the relationship of floor space or seating capacity to land use. For example, a furniture store would
require fewer off-street parking spaces in relation to the
floor area than would a movie theater.
3-5Chapter 3: Housing RegulationsHealthy Housing Reference Manual
Exceptions to the Zoning Code
Nonconforming Uses
Because zoning is not retroactive, all zoning ordinances
contain a provision for nonconforming uses. If a use has
already been established within a particular district before
the adoption of the ordinance, it must be permitted to
continue, unless it can be shown to be a public nuisance.
Provisions are, however, put into the ordinance to aid in
eliminating nonconforming uses over time. These provisions generally prohibit a) an enlargement or expansion
of the nonconforming use, b) reconstruction of the nonconforming use if more than a certain portion of the
building should be destroyed, c) resumption of the use
after it has been abandoned for a period of specified time,
and d) changing the use to a higher classification or to
another nonconforming use. Some zoning ordinances
further provide a period of amortization during which
nonconforming land use must be phased out.
Variances
Zoning ordinances contain provisions for permitting
variances and providing a method for granting these
Figure 3.1. Example of a Floor Area
Figure 3.2. Example of an Angle of Light Obstruction
variances, subject to certain specified provisions. A variance may be granted when, owing to the specific conditions or use of a particular lot, an undue hardship would
be imposed on the owner if the exact content of the ordinance is enforced. A variance may be granted due to the
shape, topography, or other characteristic of the lot. For
example, suppose an irregularly shaped lot is located in a
district having a side yard requirement of 20 feet on a
side and a total lot size requirement of 10,000 square feet.
Further suppose that this lot contains 10,200 square feet
(and thus meets the total size requirement); however, due
to the irregular shape of the lot, there would be sufficient
space for only a 15-foot side yard. Because a hardship
would be imposed on the owner if the exact letter of the
law is applied, the owner of the property could apply to
the zoning adjustment board for a variance. Because the
total area of the lot is sufficient and a lessening of the
ordinance requirements would not be detrimental to the
surrounding property, nor would it interfere with neighboring properties, a variance would probably be granted.
Note that a variance is granted to the owner under specific conditions. Should use of the property change, the
variance would be voided.
Healthy Housing Reference Manual3-6 Chapter 3: Housing Regulations
Exceptions
An exception is often confused with a variance. In every
city there are some necessary uses that do not correspond
to the permitted land uses within the district. The zoning
code recognizes, however, that if proper safeguards are
provided, these uses would not have a detrimental effect
on the district. An example would be a fire station that
could be permitted in a residential area, provided the station house is designed and the property is properly landscaped to resemble or fit in with the characteristics of the
neighborhood in which it is located.
Administration
Zoning inspectors are essential to the zoning process
because they have firsthand knowledge of a case. Often,
the zoning inspector may also be the building inspector
or housing inspector. Because the building inspector or
housing inspector is already in the field making inspections, it is relatively easy for that individual to check
compliance with the zoning ordinances. Compliance is
determined by comparing the actual land use with that
allowed for the area and shown on the zoning map.
Each zoning ordinance has a map detailing the permitted
usage for each block. Using a copy of this map, the
inspector can make a preliminary check of the land use in
the field. If the use does not conform, the inspector must
then contact the Zoning Board to see whether the property in question was a nonconforming use at the time of
the passage of the ordinance and whether an exception or
variance has been granted. In cities where up-to-date
records are maintained, the inspector can check the use in
the field.
When a violation is observed, and the property owners
are duly notified of the violation, they have the right to
request a hearing before the Zoning Board of Adjustment
(also called the Zoning Board of Appeals in some cities).
The board may uphold the zoning enforcement officer or
may rule in favor of the property owner. If the action of
the zoning officer is upheld, the property owner may, if
desired, seek relief by appealing the decision to the
courts; otherwise, the violation must be corrected to conform to the zoning code.
It is critical for the housing or building inspector and the
zoning inspector to work closely in municipalities where
these positions and responsibilities are separate.
Experience has shown that illegally converted properties
are often among the most substandard encountered in the
municipality and often contain especially dangerous
housing code violations.
In communities where the zoning code is enforced effectively, the resulting zoning compliance helps to advance,
as well as sustain, many of the minimum standards of the
housing code such as occupancy, ventilation, light, and
unimpeded egress. By the same token, building or housing inspectors can often aid the zoning inspector by helping eliminate some nonconforming uses through code
enforcement.
Housing Codes
A housing code, regardless of who promulgates it, is basically an environmental health protection code. Housing
codes are distinguished from building codes in that they
cover houses, not buildings in general. For example, the
housing code requires that walls support the weight of the
roof, any floors above, and the furnishings, occupants,
etc., within a building.
Early housing codes primarily protected only physical
health; hence, they were enforced only in slum areas. In
the 1970s, it was realized that, if urban blight and its
associated human suffering were to be controlled, housing
codes must consider both physical and mental health and
must be administered uniformly throughout the
community.
In preparing or revising housing codes, local officials
must maintain a level of standards that will not merely be
minimal. Standards should maintain a living environment
that contributes positively to healthful individual and
family living. The fact that a small portion of housing
fails to meet a desirable standard is not a legitimate reason for retrogressive modification or abolition of a standard. The adoption of a housing ordinance that
establishes low standards for existing housing serves only
to legalize and perpetuate an unhealthy living environment. Wherever local conditions are such that immediate
enforcement of some standards within the code would
cause undue hardship for some individuals, it is better to
allow some time for compliance than to eliminate an otherwise satisfactory standard. When immediate health or
safety hazards are not involved, it is often wise to attempt
to create a reasonable timetable for accomplishing necessary code modifications.
History
To assist municipalities with developing legislation necessary to regulate the quality of housing, the American
Public Health Association (APHA) Committee on the
Hygiene of Housing prepared and published in 1952 a
proposed housing ordinance. This provided a prototype
on which such legislation might be based and has served
3-7Chapter 3: Housing RegulationsHealthy Housing Reference Manual
as the basis for countless housing codes enacted in the
United States since that time. Some municipalities
enacted it without change. Others made revisions by
omitting some portions, modifying others, and sometimes adding new provisions [9].
The APHA ordinance was revised in 1969 and 1971. In
1975, APHA and the CDC jointly undertook the job of
rewriting and updating this model ordinance. The new
ordinance was entitled the APHA-CDC Recommended
Housing Maintenance and Occupancy Ordinance [10]. The
most recent model ordinance was published by APHA in
1986 as Housing and Health: APHA-CDC Recommended
Minimum Housing Standards [11]. This new ordinance is
one of several model ordinances available to communities
when they are interested in adopting a housing code.
A community should read and consider each element
within the model code to determine its applicability to
their community. A housing code is merely a means to an
end. The end is the eventual elimination of all substandard conditions within the home and the neighborhood.
This end cannot be achieved if the community adopts an
inadequate housing code.
Objectives
The Housing Act of 1949 [12] gave new impetus to
existing local, state, and federal housing programs
directed toward eliminating poor housing. In passing this
legislation, Congress defined a new national objective by
declaring that “the general welfare and security of the
nation and the health and living standards of its people...
require a decent home and a suitable living environment
for every American family.” This mandate generated an
awareness that the quality of housing and residential environment has an enormous influence upon the physical
and mental health and the social well-being of each individual and, in turn, on the economic, political, and social
conditions in every community. Consequently, public
agencies, units of government, professional organizations
and others sought ways to ensure that the quality of
housing and the residential environment did not
deteriorate.
It soon became apparent that ordinances regulating the
supplied utilities and the maintenance and occupancy of
dwellings were needed. Commonly called housing codes,
these ordinances establish minimum standards to make
dwellings safe, sanitary, and fit for human habitation by
governing their condition and maintenance, their supplied utilities and facilities, and their occupancy. The
2003 International Code Council (ICC) [13,14]
International Residential Code-One- and Two-Family
Dwellings (R101.3) states
“the purpose of this code is to provide minimum
requirements to safeguard the public safety, health and
general welfare, through affordability, structural strength,
means of egress, facilities, stability, sanitation, light
and ventilation, energy conservation, safety to fire and
property from fire and other hazards attributed to the
built environment.”
Critical Requirements of an Effective Housing Program
A housing code is limited in its effectiveness by several
factors. First, if the housing code does not contain standards that adequately protect the health and well-being of
the individuals, it cannot be effective. The best-trained
housing inspector, if not armed with an adequate housing
code, can accomplish little good in the battle against
urban blight.
A second issue in establishing an effective housing code is
the need to establish a baseline of current housing conditions. A systems approach requires that you establish
where you are, where you are going, and how you plan to
achieve your goals. In using a systems approach, it is
essential to know where the program started so that the
success or failure of various initiatives can be established.
Without this information, success cannot be replicated,
because you cannot identify the obstacles navigated nor
the elements of success. Many initiatives fail because program administrators are without the necessary proof of
success when facing funding shortfalls and budget cuts.
A third factor affecting the quality of housing codes is
budget. Without adequate funds and personnel, the community can expect to lose the battle against urban blight.
It is only through a systematic enforcement effort by an
adequately sized staff of properly trained inspectors that
the battle can be won.
A fourth factor is the attitude of the political bodies
within the area. A properly administered housing program will require upgrading substandard housing
throughout the community. Frequently, this results in
political pressures being exerted to prevent the enforcement of the code in certain areas of the city. If the housing effort is backed properly by all political elements,
blight can be controlled and eventually eliminated within
the community. If, however, the housing program is not
permitted to choke out the spreading influence of substandard conditions, urban blight will spread like a cancer, engulfing greater and greater portions of the city.
Similarly, an effort directed at only the most seriously
Healthy Housing Reference Manual3-8 Chapter 3: Housing Regulations
blighted blocks in the city will upgrade merely those
blocks, while the blight spreads elsewhere. If urban blight
is to be controlled, it must be cut out in its entirety.
A fifth element that limits housing programs is whether
they are supported fully by the other departments within
the city. Regardless of which city agency administers the
housing program, other city agencies must support the
activities of the housing program. In addition, great effort
should be expended to obtain the support and cooperation of the community. This can be accomplished
through public awareness and public information programs, which can result in considerable support or considerable resistance to the efforts of the program.
A sixth limitation is an inadequately or improperly
trained inspection staff. Inspectors should be capable of
evaluating whether a serious or a minor problem exists in
matters ranging from the structural stability of a building
to the health and sanitary aspects of the structure. If they
do not have the authority or expertise, they should
develop that expertise or establish effective and efficient
agreements with overlapping agencies to ensure timely
and appropriate response.
A seventh item that frequently restricts the effectiveness
of a housing program is the fact that many housing
groups fail to do a complete job of evaluating housing
problems. The deterioration of an area may be due to factors such as housing affordability, tax rates, or issues
related to investment cost and return. In many cases, the
inspection effort is restricted to merely evaluating the
conditions that exist, with little or no thought given to
why these conditions exist. If a housing effort is to be
successful, as part of a systems approach, the question of
why the homes deteriorated must be considered. Was it
because of environmental stresses within the neighborhood that need to be eliminated or was it because of apathy on the part of the occupants? In either case, if the
causative agent is not removed, then the inspector faces
an annual problem of maintaining the quality of that residence. It is only by eliminating the causes of deterioration
that the quality of the neighborhood can be maintained.
Often the regulatory authority does not have adequate
authority within the enabling legislation of the code
needed to resolve the problem or there are gaps in
jurisdiction.
Content of a Housing Code
Although all comprehensive housing codes or ordinances
contain a number of common elements, the provisions of
communities will usually vary. These variations stem from
differences in local policies, preferences, and, to a lesser
extent, needs. They are also influenced by the standards
set by the related provisions of the diverse building, electrical, and plumbing codes in use in the municipality.
Within any housing code there are generally five features:
1. Definitions of terms used in the code.
2. Administrative provisions showing who is authorized to
administer the code and the basic methods and procedures
that must be followed in implementing and enforcing the
sections of the code. Administrative provisions deal with
items such as reasonable hours of inspections, whether
serving violation notices is required, how to notify
absentee owners or resident-owners or tenants, how to
process and conduct hearings, what rules to follow in
processing dwellings alleged to be unfit for human
habitation, and how to occupy or use dwellings finally
declared fit.
3. Substantive provisions specifying the various types of
health, building, electrical, heating, plumbing,
maintenance, occupancy, and use conditions that
constitute violations of the housing code. These provisions
can be and often are grouped into three categories:
minimum facilities and equipment for dwelling units;
adequate maintenance of dwellings and dwelling units, as
well as their facilities and equipment; and occupancy
conditions of dwellings and dwelling units.
4. Court and penalty sections outlining the basis for court
action and thepenalty or penalties to which the alleged
violator will be subjected if proved guilty of violating one
or more provisions of the code.
5. Enabling, conflict, and unconstitutionality clauses
providing the date a new or amended code will take effect,
prevalence of more stringent provision when there is a
conflict of two codes, severability of any part of the
ordinance that might be found unconstitutional, and
retention of all other parts in full course and effect. In any
city following the format of the APHA-CDC
Recommended Housing Maintenance and Occupancy
Ordinance [10] the housing officer or other supervisor in
charge of housing inspections will also adopt appropriate
housing rules and regulations from time to time to clarify
or further refine the provisions of the ordinance. When
rules and regulations are used, care should be taken that
the department is not overburdened with a number of
minor rules and regulations. Similarly, a housing
ordinance that encompasses all rules and regulations might
have difficulty because any amendments to it will require
action by the political element of the community. Some
3-9Chapter 3: Housing RegulationsHealthy Housing Reference Manual
housing groups, in attempting to obtain amendments to
an ordinance, have had the entire ordinance thrown out
by the political bodies.
Administrative Provisions of a Housing Code
The administrative procedures and powers of the housing
inspection agency, its supervisors, and its staff are similar
to other provisions in that all are based on the police
power of the state to legislate for public health and safety.
In addition, the administrative provisions, and to a lesser
extent, the court and penalty provisions, outline how the
police power is to be exercised in administering and
enforcing the code.
Generally, the administrative elements deal with procedures for ensuring that the constitutional doctrines of reasonableness, equal protection under the law and due
process of law are observed. They also must guard against
violation of prohibitions against unlawful search and seizure, impairment of obligations of contract, and unlawful
delegation of authority. These factors encompass items of
great importance to housing inspection supervisors such
as the inspector’s right of entry, reasonable hours of
inspection, proper service, and the validity of the provisions of the housing codes they administer.
Owner of Record. It is essential to file legal actions
against the true owners of properties in violation of housing codes. With the advent of the computer, this is often
much easier than in the past. Databases that provide this
information are readily available from many offices of
local government such as the tax assessment office. The
method of obtaining the name and address of the legal
owner of a property in violation varies from place to
place. Ordinarily, a check of the city tax records will suffice unless there is reason to believe these are not up to
date. In this case, a further check of county or parish
records will turn up the legal owner if state law requires
deed registration there. If it does not, the advice of the
municipal law department should be sought about the
next steps to follow.
Due Process Requirements. Every notice, complaint,
summons, or other type of legal paper concerning alleged
housing code violations in a given dwelling or dwelling
unit must be legally served on the proper party to be valid
and to prevent harassment of innocent parties. This might
be the owner, agent, or tenant, as required by the code. It
is customary to require that the notice to correct existing
violations and any subsequent notices or letters be served
by certified or registered mail with return receipt requested. The receipt serves as proof of service if the case has to
be taken to court.
Due process requirements also call for clarity and specificity with respect to the alleged violations, both in the violation notices and the court complaint-summons. For this
reason, special care must be taken to be complete and
accurate in listing the violations and charges. To illustrate,
rather than direct the violator to repair all windows where
needed, the violator should be told exactly which windows and what repairs are involved.
The chief limitation on the due process requirement, with
respect to service of notices, lies in cases involving immediate threats to health and safety. In these instances, the
inspection agency or its representative may, without notice
or hearing, issue an order citing the existence of the emergency and requiring that action deemed necessary to meet
the emergency be taken.
In some areas housing courts on the municipal level have
advocates that assist both plaintiffs and defendants prepare for the court process or to resolve the issue to avoid
court.
Hearings and Condemnation Power. The purpose of a
hearing is to give the alleged violator an opportunity to be
heard before further action is taken by the housing inspection agency. These hearings may be very informal, involving meetings between a representative of the agency and
the person ordered to take corrective action. They also
may be formal hearings at which the agency head presides
and at which the city and the defendant both are entitled
to be represented by counsel and expert witnesses.
Informal Hearings. A violator may have questions about a
violation notice or the notice may be served at a time
when personal hardship or other factors prevent a violator
from meeting the terms of the notice. Therefore, many
housing codes provide the opportunity for a hearing at
which the violator may discuss questions or problems and
seek additional time or some modification of the order.
Administered in a firm but understanding manner, these
hearings can serve as invaluable aids in relieving needless
fears of those involved, in showing how the inspection
program is designed to help them and in winning their
voluntary compliance.
Formal Hearings. Formal hearings are often quasijudicial
hearings (even though the prevailing court rules of evidence do not always apply) from which an appeal may be
taken to court. All witnesses must therefore be sworn in,
and a record of the proceedings must be made. The formal hearing is used chiefly as the basis for determining
whether a dwelling is fit for human habitation, occupancy, or use. In the event it is proved unfit, the building
is condemned and the owner is given a designated
Healthy Housing Reference Manual3-10 Chapter 3: Housing Regulations
amount of time either to rehabilitate it completely or to
demolish it. Where local funds are available, a municipality may demolish the building and place a lien against the
property to cover demolition costs if the owner fails to
obey the order within the time specified. This type of
condemnation hearing is a very effective means of stimulating prompt and appropriate corrective action when it is
administered fairly and firmly.
Procedures for Coping With Common Problems. Several states and local communities have developed innovative ways to resolve code violation issues.
Limitation of Occupancy Notification. This technique was
pioneered in Wilmington, Delaware. It makes it mandatory for property owners in the community to obtain a
legal notice from the housing inspection agency specifying the maximum number of persons that may occupy
each of their properties. It also requires these owners to
have a residence, place of business, or an agent for their
properties within the community. The agent should be
empowered to take remedial action on any of the properties found in violation. In addition, if the property is
sold, the new owner must obtain a new Limitation of
Occupancy Notification.
Request for Inspections. Several states permit their municipalities to offer a request for inspection service. For a fee,
the housing inspector will inspect a property for violations of the housing code before its sale so that the buyer
can learn its condition in advance. Many states and localities now require owners to notify prospective purchasers
of any outstanding notice of health risk or violations they
have against their property before the sale. If they fail to
do so, some codes will hold the owner liable to the purchaser and the inspection agency for violations.
Tickets for Minor Offenses. Denver, Colorado, has used
minimal financial fines to prod minor violators and first
offenders into correcting violations without the city
resorting to court action. There are mixed views about
this technique because it is akin to formal police action.
Nevertheless, the action may stimulate compliance and
reduce the amount of court action needed to achieve it.
Forms and Form Letters. A fairly typical set of forms
and form letters are described below. It should be stressed
that inspection forms to be used for legal notices must
satisfy legal standards of the code, be meaningful to the
owner and sufficiently explicit about the extent and location of particular defects, be adaptable to statistical compilation for the governing body reports, and be written in
a manner that will facilitate clerical and other administrative usage.
The Daily Report Form. This form gives the inspection
agency an accurate basis for reporting, evaluating, and, if
necessary, improving the productivity and performance of
its inspectors.
Complaint Form. This form helps obtain full information
from the complainant and thus makes the relative seriousness of the problem clear and reduces the number of
crank complaints.
No-entry Notice. This notice advises occupants or owners
that an inspector was there and that they must return a
call to the inspector.
Inspection Report Form. This is the most important form
in an agency. It comes in countless varieties, but if
designed properly, it will ensure more productivity and
more thoroughness by the inspectors, reduce the time
spent in writing reports, locate all violations correctly, and
reduce the time required for typing violation notices.
Forms may vary widely in sophistication from a very simple form to one whose components are identified by
number for use in processing the case by automation.
Some forms are a combined inspection report and notice
form in triplicate so that the first page can be used as the
notice of violation, the second as the office record, and
the third as the guide for reinspection. A covering form
letter notifies the violator of the time allowed to correct
the conditions listed in the report form.
Violation Notice. This is the legal notice that housing code
violations exist and must be corrected within the indicated amount of time. The notice may be in the form of
a letter that includes the alleged violations or has a copy
of these attached. It may be a standard notice form, or it
may be a combined report-notice. Regardless of the type
of notice used, it should make the location and nature of
all violations clear and specify the exact section of the
code that covers each one. The notice must advise violators of their right to a hearing. It should also indicate that
the violator has a right to be represented by counsel and
that failure to obtain counsel will not be accepted as
grounds for postponing a hearing or court case.
Hearing Forms. These should include a form letter notifying the violator of the date and time set for the hearing, a
standard summary sheet on which the supervisor can
record the facts presented at an informal hearing, and a
hearing-decision letter for notifying all concerned of the
hearing results. The latter should include the names of
the violator, inspector, law department, and any other
city official or agency that may be involved in the case.
3-11Chapter 3: Housing RegulationsHealthy Housing Reference Manual
Reinspection Form Letters or Notices. These have the same
characteristics as violation notices except that they cover
the follow-up orders given to the violator who has failed
to comply with the original notice within the time specified. Some agencies may use two or three types of these
form letters to accommodate different degrees of response
by the violator. Whether one or several are used, standardization of these letters or notices will expedite the
processing of cases.
Court Complaint and Summons Forms. These forms advise
alleged violators of the charges against them and summon
them to appear in court at the specified time and place. It
is essential that the housing inspection agency work
closely with the municipal law department in preparing
these forms so that each is done in exact accord with the
rules of court procedure in the relevant state and
community.
Court Action Record Form. This form provides an accurate
running record of the inspection agency’s court actions
and their results.
Substantive Provisions of a Housing Code
A housing code is the primary tool of the housing inspector. The code spells out what the inspector may or may
not do. An effort to improve housing conditions can be
no better than the code allows. The substantive provisions
of the code specify the minimal housing conditions
acceptable to the community that developed them.
Dwelling units should have provisions for preparing at
least one regularly cooked meal per day. Minimum equipment should include a kitchen sink in good working condition and properly connected to the water supply system
approved by the appropriate authority. It should provide,
at all times, an adequate amount of heated and unheated
running water under pressure and should be connected to
a sewer system approved by the appropriate authority.
Cabinets or shelves, or both, for storing eating, drinking,
and cooking utensils and food should be provided. These
surfaces should be of sound construction and made of
material that is easy to clean and that will not have a
toxic or deleterious effect on food.
In addition, a stove and refrigerator should be provided.
Within every dwelling there should be a room that
affords privacy and is equipped with a flush toilet in good
working condition.
Within the vicinity of the flush toilet, a sink should be
provided. In no case should a kitchen sink substitute as a
lavatory sink. In addition, within each dwelling unit there
should be, within a room that affords privacy, either a
bathtub or shower or both, in good working condition.
Both the lavatory sink and the bathtub or shower or both
should be equipped with an adequate amount of heated
and unheated water under pressure. Each should be connected to an approved sewer system.
Within each dwelling unit two or more means of egress
should be provided to safe and open space at ground
level. Provisions should be incorporated within the housing code to meet the safety requirements of the state and
community involved. The housing code should spell out
minimum standards for lighting and ventilation within
each room in the structure. In addition, minimum thermal standards should be provided. Although most codes
merely provide the requirement of a given temperature at
a given height above floor level, the community should
give consideration to the use of effective temperatures.
The effective temperature is a means of incorporating not
only absolute temperature in degrees, but also humidity
and air movement, giving a better indication of the comfort index of a room.
The code should provide that no person shall occupy or
let for occupancy any dwelling or dwelling units that do
not comply with stated requirements. Generally, these
requirements specify that the foundation, roof, exterior
walls, doors, window space and windows of the structure
be sound and in good repair; that it be moisture-free,
watertight and reasonably weather tight and that all structural surfaces be sound and in good repair.
HUD defines a multifamily dwelling unit as one that
contains four or more dwelling units in a single structure.
A dwelling unit is further defined as a single unit of residence for a family of one or more persons in which sleeping accommodations are provided but toileting or
cooking facilities are shared by the occupants.
Building Codes
Building codes define what materials and methods are
tobe used in the construction of various buildings. Model
building codes have been published by various trade organizations such as the Southern Building Code Congress
International (SBCCI), Building Officials and Code
Administrators (BOCA), and the International
Conference of Building Officials (ICBO). Each of these
groups published a model building code that was widely
used or adapted regionally in the United States. BOCA
national codes were used mostly in eastern and Great
Lakes states, ICBO uniform codes in western and
Midwest states, and SBCCI standard codes in southern
states. As a result, the construction industry often faced
Healthy Housing Reference Manual3-12 Chapter 3: Housing Regulations
the challenge, and cost, of building to different codes in
different areas of the country.
In 1994, BOCA, ICBO, and SBCCI created the
International Code Council (ICC) to develop a single set
of comprehensive, coordinated model construction codes
that could be used throughout the United States and
around the world. The first I-Code published was the
International Plumbing Code in 1995. By 2000, a complete family of I-Codes was available, including the
International Building Code. The ICC Performance
Code for Buildings and Facilities joined the I-Code family in 2001.
On February 1, 2003, the three organizations (BOCA,
SBCCI, and ICBO) were consolidated into the ICC
[13,14]. According to ICC Board president, Paul E.
Myers,
“The ICC International Codes (I Codes) combine the
strengths of the regional codes without regional limitations. The ICC is a nonprofit organization dedicated to
developing a single set of comprehensive and coordinated
national codes to make compliance easier and more costeffective. I Codes respond to the needs of the construction
industry and public safety. A single set of codes has strong
support from government, code enforcement officials, fire
officials, architects, engineers, builders, developers, and
building owners and managers.”
References
1. Hammurabi’s Code of Laws. Translated by L.W. King.
Available from URL: http://eawc.evansville.edu/anthology/
hammurabi.htm.
2. Claghorn KH. The foreign immigrant in New York City.
Reports of the Industrial Commission, Volume XV.
Washington, DC: US Government Printing Office;
1901.p. 465-92. Available from URL: http://tenant.net/
Community/LES/clag2.html.
3. Riis J. How the other half lives— studies among the
tenements of New York. New York: Charles Scriber’s Sons;
1890. Available from URL: http://www.bartleby.
com/208/.
4. New York City Department of City Planning. New York
City zoning: zoning history. New York City: New York
City Department of City Planning; no date. Available
from URL: http://www.nyc.gov/html/dcp/html/zone/
zonehis.html.
5. New York State Multiple Dwelling Law: chapter 713 of
the Laws of 1929, as amended. Available from URL:
http://tenant.net/Other_Laws/MDL/mdltoc.html.
6. Understanding Fannie Mae: our history. Washington,
DC: Fannie Mae; 2005. Available from URL: http://www.
fanniemae.com/aboutfm/understanding/history.jhtml?p=
About+Fannie+Mae&s=Understanding+Fannie+Mae&t=
Our+History.
7. Paulson PB. Protecting zoning laws. Atlanta: North
Buckhead Civic Association; 2000 18 Mar. Available from
URL: http://www.nbca.org/TAP_AJC_3-18.htm.
8. Municipal Code Corporation. Municipal building codes
(online library). Tallahassee, FL: Municipal Code
Corporation. Available from URL: http://www.municode.
com/resources/online_codes.asp.
9. American Public Health Association. Housing ordinance.
Am J Public Health 1952 Jan;42(1):76–7.
10. US Public Health Service. APHA-CDC recommended
housing maintenance and occupancy ordinance. Atlanta:
US Department of Health and Human Services; 1975.
11. American Public Health Association. Housing and health:
APHA-CDC recommended minimum housing
standards. Washington, DC: American Public Health
Association; 1986.
12. Lang RE, Sohmer RR, editors. Legacy of the Housing Act
of 1949: The past, present, and future of federal housing
and urban policy. Housing Policy Debate 2000;11(2):
291–7. Available from URL: http://www.
fanniemaefoundation.org/programs/hpd/pdf/ hpd_ 1102_
edintro.pdf.
13. International Code Council. International residential code
2003. Country Club Hills, IL: ICC; 2003.
14. International Code Council. International building code
2003. Country Club Hills, IL: ICC; 2003.
Additional Sources of Information
American Planning Association. Available from URL:
http://www.planning.org/.
Arendt R. “Open Space” zoning: what it is and why it
works. Planners Commission Journal 1992. Available
from URL: http://www.plannersweb.com/articles/are015.
html.
Bookmark, Inc. Available from URL: http://www.bookmarki.com.
3-13Chapter 3: Housing RegulationsHealthy Housing Reference Manual
International Code Council. Available from URL:
http://www.iccsafe.org.
Rosenberg M. Zoning: residential, commercial, or industrial? New York: About, Inc.; no date. Available from
URL: http://geography.about.com/library/weekly/
aa072801a.htm?iam=sherlock_abc/.
US Department of Energy, Land Use Planning. Smart
Communities Network. Washington, DC: US
Department of Energy; no date. Available from URL:
http://www. smartcommunities.ncat.org/landuse/luintro.
shtml.
US Department of Housing and Urban Development.
Available from URL: http://www.hud.gov/.
US Department of Housing and Urban Development.
Final report of HUD review of model building codes.
Washington, DC: US Department of Housing and
Urban Development; no date. Available from URL:
http://www.hud.gov/offices/fheo/disabilities/modelcodes/
chapter5.html.
Healthy Housing Reference Manual3-14 Chapter 3: Housing Regulations
4-1Chapter 4: Disease Vectors and PestsHealthy Housing Reference Manual
“Sometimes poor housing is a shorthand way of describing
living conditions of poor people. The poor include the aged,
deprived, ethnic minority groups, the infirmed, and families
headed by unemployed women. In other words, the people
most at risk for illness often live in inferior housing.
Therefore, it is a matter of conjecture whether many people
live in poor housing because they are sick or are sick because
they live in poor housing.”
Carter L. Marshall, M.D.
Dynamics of Health and Disease
Appleton, Century Crofts 1972
Introduction
The most immediate and obvious link between housing
and health involves exposure to biologic, chemical, and
physical agents that can affect the health and safety of the
occupants of the home. Conditions such as childhood
lead poisoning and respiratory illnesses caused by exposure to radon, asbestos, tobacco smoke, and other pollutants are increasingly well understood and documented.
However, even 50 years ago, public health officials understood that housing conditions were linked to a broader
pattern of community health. For example, in 1949, the
Surgeon General released a report comparing several
health status indicators among six cities having slums.
The publication reported that:
• the rate of deaths from communicable disease in these
areas was the same as it was for the rest of the country
50 years ago (i.e., around 1900);
• most of the tuberculosis cases came from 25% of the
population of these cities; and
• the infant mortality rate was five times higher than in
the rest of the country, approximately equal to what it
was 50 years ago.
Housing-related health concerns include asthma episodes
triggered by exposure to dust mites, cockroaches, pets,
and rodents. The existence of cockroaches, rats, and mice
mean that they can also be vectors for significant problems that affect health and well-being. They are capable
of transmitting diseases to humans. According to a 1997
American Housing Survey, rats and mice infested 2.7 million of 97 million housing units. A CDC-sponsored survey of two major American cities documented that nearly
50% of the premises were infected with rats and mice.
This chapter deals with disease vectors and pests as factors related to the health of households.
Disease Vectors and Pests
Integrated pest management (IPM) techniques are necessary to reduce the number of pests that threaten human
health and property. This systems approach to the problem relies on more than one technique to reduce or eliminate pests. It can be visualized best as concentric rings of
protection that reduce the need for the most risky and
dangerous options of control and the potential for pests
to evolve and develop. It typically involves using some or
all of the following steps:
• monitoring, identifying, and determining the level of
threat from pests;
• making the environment hostile to pests;
• building the pests out by using pest-proof building
materials;
• eliminating food sources, hiding areas, and other pest
attractants;
• using traps and other physical elimination devices; and
• when necessary, selecting appropriate poisons for
identified pests.
The above actions are discussed in more detail in the following section on the four basic strategies for controlling
rodents.
Most homeowners have encountered a problem with
rodents, cockroaches, fleas, flies, termites, or fire ants.
These pests destroy property or carry disease, or both,
and can be a problem for rich and poor alike.
Rodents
Rodents destroy property, spread disease, compete for
human food sources, and are aesthetically displeasing.
Rodent-associated diseases affecting humans include
plague, murine typhus, leptospirosis, rickettsialpox, and
rat-bite fever. The three primary rodents of concern to
the homeowner are the Norway rat (Rattus norvegicus),
roof rat (Rattus rattus), and the house mouse (Mus musculus). The term “commensal” is applied to these rodents,
meaning they live at people’s expense. The physical traits
of each are demonstrated in Figure 4.1.
Chapter 4: Disease Vectors and Pests
Healthy Housing Reference Manual4-2 Chapter 4: Disease Vectors and Pests
Barnett [1] notes that the house mouse is abundant
throughout the United States. The Norway rat (Figure
4.2) is found throughout the temperate regions of the
world, including the United States. The roof rat is found
mainly in the South, across the entire nation to the
Pacific coast. As a group, rodents have certain behavioral
characteristics that are helpful in understanding them.
They are perceptive to touch, with sensitive whiskers and
guard hairs on their bodies. Thus, they favor running
along walls and between objects that allow them constant
contact with vertical surfaces.
They are known to have
poor eyesight and are alleged
to be colorblind.
Contrastingly, they have an
extremely sharp sense of
smell and a keen sense of
taste. The word rodent is
derived from the Latin verb
rodere, meaning “to gnaw.”
The gnawing tendency leads
to structural damage to
buildings and initiates fires
when insulation is chewed
from electrical wires. Rodents will gnaw to gain entrance
and to obtain food.
Figure 4.1. Field Identification of Domestic Rodents [2]
Figure 4.2. Norway Rat [3]
The roof rat (Figure 4.3) is a slender, graceful, and very
agile climber. The roof rat prefers to live aboveground:
indoors in attics, between floors, in walls, or in enclosed
spaces; and outdoors in trees and dense vine growth.
Contrasted with the
roof rat, the Norway rat
is at home below the
ground, living in a burrow. The house mouse
commonly is found living in human quarters,
as suggested by its
name. Signs indicative
of the presence of
rodents— aside from seeing live or dead rats and hearing
rats— are rodent droppings, runways, and tracks (Figure
4.4). Other signs include nests, gnawings, food scraps, rat
hair, urine spots, and rat body odors. Note that waste
droppings from rodents are often confused with cockroach egg packets, which are smooth, segmented, and
considerably smaller than a mouse dropping.
According to the Military Pest Management Handbook
(MPMH) [2], rats and mice are very suspicious of any
new objects or food found in their surroundings. This
characteristic is one reason rodents can survive in dangerous environments. This avoidance reaction accounts for
Figure 4.3. Roof Rat [4]
4-3Chapter 4: Disease Vectors and PestsHealthy Housing Reference Manual
prebaiting (baiting without poisoning) in control programs. Initially, rats or mice begin by taking only small
amounts of food. If the animal becomes ill from a sublethal dose of poison, its avoidance reaction is strengthened, and a poisoning program becomes extremely
difficult to complete. If rodents are hungry or exposed to
an environment where new objects and food are commonly found, such as a dump, their avoidance reaction
may not be as strong; in extreme cases of hunger, it may
even be absent.
The first of four basic strategies for controlling rodents is
to eliminate food sources. To accomplish this, it is
imperative for the homeowner or occupant to do a good
job of solid waste management. This requires proper storing, collecting, and disposing of refuse.
The second strategy is to eliminate breeding and nesting places. This is accomplished by removing rubbish
from near the home, including excess lumber, firewood,
and similar materials. These items should be stored above
ground with 18 inches of clearance below them. This
height does not provide a habitat for rats, which have a
propensity for dark, moist places in which to burrow.
Wood should not be stored directly on the ground, and
trash and similar rubbish should be eliminated.
Figure 4.4. Signs of Rodent Infestation [2]
The third strategy is to construct buildings and other
structures using rat-proofing methods. MPMH notes
that it is much easier to manage rodents if a structure is
built or modified in a way that prevents easy access by
rodents. Tactics for rodent exclusion include building or
covering doors and windows with metal. Rats can gnaw
through wooden doors and windows in a very short time
to gain entrance. All holes in a building’s exterior should
be sealed. Rats are capable of enlarging openings in
masonry, especially if the mortar or brick is of poor quality. All openings more than ¾-inch wide should be
closed, especially around pipes and conduits. Cracks
around doors, gratings, windows, and other such openings should be covered if they are less than 4 feet above
the ground or accessible from ledges, pipes, or wires
(Figure 4.5).
Additional tactics include using proper materials for rat
proofing. For example, sheet metal of at least 26-gauge,
¼-inch or ½-inch hardware cloth, and cement are all
suitable rat-resistant materials. However, ½-inch hardware
cloth has little value against house mice. Tight fittings
and self-closing doors should be constructed. Rodent
runways can be behind double walls; therefore, spaces
between walls and floor-supporting beams should be
blocked with fire stops. A proper rodent-proofing strategy
must bear in mind that rats can routinely jump 2 feet
vertically, dig 4 feet or more to get under a foundation,
climb rough walls or smooth pipes up to 3 inches in
diameter, and routinely travel on electric or telephone
wires.
The first three strategies— good sanitation techniques,
habitat denial, and rat proofing— should be used initially
in any rodent management program. Should they fail, the
fourth strategy is a killing program, which can vary from
a family cat to the professional application of rodenticides. Cats can be effective against mice, but typically are
not useful against a rat infestation. Over-the-counter
rodenticides can be purchased and used by the homeowner or occupant. These typically are in the red squill or
warfarin groups.
A more effective alternative is trapping. There are a variety of devices to choose from when trapping rats or mice.
The two main groups of rat and mouse traps are live
traps (Figure 4.6) and kill traps (Figure 4.7). Traps usually
are placed along walls, near runways and burrows, and in
other areas. Bait is often used to attract the rodents to the
trap. To be effective, traps must be monitored and emptied or removed quickly. If a rat caught in a trap is left
there, other rats may avoid the traps. A trapping strategy
also may include using live traps to remove these vermin.
Healthy Housing Reference Manual4-4 Chapter 4: Disease Vectors and Pests
Cockroaches
Cockroaches have become well adapted to living with
and near humans, and their hardiness is legendary. In
light of these facts, cockroach control may become a
homeowner’s most difficult task because of the time and
special knowledge it often involves. The cockroach is
considered an allergen source and an asthma trigger for
residents. Although little evidence exists to link the cockroach to specific disease outbreaks, it has bee demonstrated to carry Salmonella typhimurium, Entamoeba
histolytica, and the poliomyelitis virus. In addition,
Kamble and Keith [6] note that most cockroaches produce a repulsive odor that can be detected in infested
areas. The sight of cockroaches can cause considerable
psychologic or emotional distress in some individuals.
They do not bite, but they do have heavy leg spines that
may scratch.
According to MPMH [2], there are 55 species of cockroaches in the United States. As a group, they tend to
prefer a moist, warm habitat because most are tropical in
origin. Although some tropical cockroaches feed only on
vegetation, cockroaches of public health interest tend to
live in structures and are customarily scavengers.
Cockroaches will eat a great variety of materials, including cheese and bakery products, but they are especially
fond of starchy materials, sweet substances, and meat
products.
Cockroaches are primarily nocturnal. Daytime sightings
may indicate potentially heavy infestations. They tend to
hide in cracks and crevices and can move freely from
room to room or adjoining housing units via wall spaces,
plumbing, and other utility installations. Entry into
homes is often accomplished through food and beverage
Figure 4.7. Kill Traps for Rats [2]
Figure 4.5. Rodent Prevention [2]
Figure 4.6. Live Traps for Rats [5]
4-5Chapter 4: Disease Vectors and PestsHealthy Housing Reference Manual
boxes, grocery sacks, animal food, and household goods
carried into the home. The species of public health interest that commonly inhabit human dwellings (Figures
4.8–4.13) include the following: German cockroach
(Blattella germanica); American cockroach (Periplaneta
americana); Oriental cockroach (Blatta orientalis); brownbanded cockroach (Supella longipalpa); Australian cockroach (Periplaneta australasiae); smoky-brown cockroach
(Periplaneta fuliginosa); and brown cockroach (Periplaneta
brunnea).
Four management strategies exist for controlling cockroaches. The first is prevention. This strategy includes
inspecting items being carried into the home and sealing
cracks and crevices in kitchens, bathrooms, exterior
doors, and windows. Structural modifications would
include weather stripping and pipe collars. The second
strategy is sanitation. This denies cockroaches food,
water, and shelter. These efforts include quickly cleaning
food particles from shelving and floors; timely washing of
dinnerware; and routine cleaning under refrigerators,
stoves, furniture, and similar areas. If pets are fed indoors,
pet food should be stored in tight containers and not left
in bowls overnight. Litter boxes should be cleaned routinely. Access should be denied to water sources by fixing
Figure 4.8. American, Oriental, German, and Brown-banded
Cockroaches [7]
Figure 4.9. American Cockroaches, Various Stages and Ages [7]
Figure 4.10. Oriental Cockroaches, Various Stages and Ages [7]
Figure 4.11. German Cockroaches, Various Stages and Ages [7]
Figure 4.12. Brown-banded Cockroaches, Various Stages and
Ages [7]
Figure 4.13. Wood Cockroach, Adult Male [7]
Healthy Housing Reference Manual4-6 Chapter 4: Disease Vectors and Pests
leaking plumbing, drains, sink traps, and purging clutter,
such as papers and soiled clothing and rags. The third
strategy is trapping. Commercially available cockroach
traps can be used to capture roaches and serve as a monitoring device. The most effective trap placement is against
vertical surfaces, primarily corners, and under sinks, in
cabinets, basements, and floor drains. The fourth strategy
is chemical control. The use of chemicals typically indicates that the other three strategies have been applied
incorrectly. Numerous insecticides are available and
appropriate information is obtainable from EPA.
Fleas
The most important fleas as disease vectors are those that
carry murine typhus and bubonic plague. In addition,
fleas serve as intermediate hosts for some species of dog
and rodent tapeworms that occasionally infest people.
They also may act as intermediate hosts of filarial worms
(heartworms) in dogs. In the United States, the most
important disease related to fleas is the bubonic plague.
This is primarily a concern of residents in the southwestern and western parts of the country (Figure 4.14).
Of approximately 2,000 species of flea, the most common flea infesting both dogs and cats is the cat flea
Ctenocephalides felis. Although numerous animals, both
wild and domestic, can have flea infestations, it is from
the exposure of domestic dogs and cats that most homeowners inherit flea infestation problems. According to
MPMH [2], fleas are wingless insects varying from 1 to
8½ millimeters (mm) long, averaging 2 to 4 mm, and
feed through a siphon or tube. They are narrow and compressed laterally with backwardly directed spines, which
adapt them for moving between the hairs and feathers of
mammals and birds. They have long, powerful legs
adapted for jumping. Both sexes feed on blood, and the
female requires a blood meal before she can produce viable eggs. Fleas tend to be host-specific, thus feeding on
only one type of host. However, they will infest other
species in the absence of the favored host. They are found
in relative abundance on animals that live in burrows and
sheltered nests, while mammals and birds with no permanent nests or that are exposed to the elements tend to
have light infestations.
MPMH [2] notes that fleas undergo complete metamorphosis (egg, larva, pupa, and adult). The time it takes to
complete the life cycle from egg to adult varies according
to the species, temperature, humidity, and food availability. Under favorable conditions, some species can complete a generation in as little as 2 or 3 weeks. Figure 4.15
shows the life cycle of the flea.
Figure 4.14. Reported Human Plague Cases (1970–1997) [8]
Figure 4.15. Flea Life Cycle [2]
4-7Chapter 4: Disease Vectors and PestsHealthy Housing Reference Manual
Flies
The historical attitude of Western society toward flies has
been one of aesthetic disdain. The public health view is to
classify flies as biting or nonbiting. Biting flies include
sand flies, horseflies, and deerflies. Nonbiting flies include
houseflies, bottleflies, and screwworm flies. The latter
group is often referred to as synanthropic because of their
close association with humans. In general, the presence of
flies is a sign of poor sanitation. The primary concern of
most homeowners is nonbiting flies.
According to MPMH [2], the housefly (Musca domestica)
(Figure 4.16) is one of the most widely distributed
insects, occurring throughout the United States, and is
usually the predominant fly species in homes and restaurants. M. domestica is also the most prominent human-associated (synanthropic) fly in the southern United States.
Because of its close
association with
people, its abundance, and its ability to transmit
disease, it is considered a greater threat
to human welfare
than any other species of nonbiting
fly. Each housefly
can easily carry more than 1 million bacteria on its body.
Some of the disease-causing agents transmitted by houseflies to humans are Shigella spp. (dysentery and diarrhea =
shigellosis), Salmonella spp. (typhoid fever), Escherichia
coli, (traveler’s diarrhea), and Vibrio cholera (cholera).
Sometimes these organisms are carried on the fly’s tarsi or
body hairs, and frequently they are regurgitated onto
food when the fly attempts to liquefy it for ingestion.
The fly life cycle is similar across the synanthropic group.
MPMH [2] notes that the egg and larval stages develop in
animal and vegetable refuse. Favorite breeding sites
include garbage, animal manure, spilled animal feed, and
soil contaminated with organic matter. Favorable environmental conditions will result in the eggs hatching in 24
hours or less. Normally, a female fly will produce 500 to
600 eggs during her lifetime.
The creamy, white larvae (maggots) are about ½-inch
long when mature and move within the breeding material
to maintain optimum temperature and moisture conditions. This stage lasts an average of 4 to 7 days in warm
weather. The larvae move to dry parts of the breeding
medium or move out of it onto the soil or sheltered
Flea eggs usually are laid singly or in small groups among
the feathers or hairs of the host or in a nest. They are
often laid in carpets of living quarters if the primary host
is a household pet. Eggs are smooth, spherical to oval,
light colored, and large enough to be seen with the naked
eye. An adult female flea can produce up to 2,000 eggs in
a lifetime. Flea larvae are small (2 to 5 mm), white, and
wormlike with a darker head and a body that will appear
brown if they have fed on flea feces. This stage is mobile
and will move away from light, thus they typically will be
found in shaded areas or under furniture. In 5 to 12 days,
they complete the three larval stages; however, this may
take several months depending on environmental conditions. The larvae, after completing development, spin a
cocoon of silk encrusted with granules of sand or various
types of debris to form the pupal stage. The pupal stage
can be dormant for 140 to 170 days. In some areas of the
country, fleas can survive through the winter. The pupae,
after development, are stimulated to emerge as adults by
movement, pressure, or heat. The pupal form of the flea
is resistant to insecticides. An initial treatment, while killing egg, larvae, and adult forms, will not kill the pupae.
Therefore, a reapplication will often be necessary. The
adult forms are usually ready to feed about 24 hours after
they emerge from the cocoon and will begin to feed
within 10 seconds of landing on a host. Mating usually
follows the initial blood meal, and egg production is initiated 24 to 48 hours after consuming a blood meal. The
adult flea lives approximately 100 days, depending on
environmental conditions.
Following are some guidelines for controlling fleas:
• The most important principle in a total flea control
program is simultaneously treating all pets and their
environments (indoor and outdoor).
• Before using insecticides, thoroughly clean the
environment, removing as many fleas as possible,
regardless of the form. This would include indoor
vacuuming and carpet steam cleaning. Special
attention should be paid to source points where pets
spend most of their time.
• Outdoor cleanup should include mowing, yard
raking, and removing organic debris from flowerbeds
and under bushes.
• Insecticide should be applied to the indoor and
outdoor environments and to the pet.
• Reapplication to heavily infested source points in the
home and the yard may be needed to eliminate preemerged adults.
Figure 4.16. Housefly [Musca domestica][9]
Healthy Housing Reference Manual4-8 Chapter 4: Disease Vectors and Pests
places under debris to pupate, with this stage usually lasting 4 to 5 days. When the pupal stage is accomplished, the
adult fly exits the puparium, dries, hardens, and flies away to
feed, with mating occurring soon after emergence. Figure
4.17 demonstrates the typical fly life cycle.
The control of the housefly is hinged on good sanitation
(denying food sources and breeding sites to the fly). This
includes the proper disposal of food wastes by placing
garbage in cans with close-fitting lids. Cans need to be
periodically washed and cleaned to remove food debris.
The disposal of garbage in properly operated sanitary
landfills is paramount to fly control.
The presence of adult flies can be addressed in various
ways. Outside methods include limited placement of
common mercury vapor lamps that tend to attract flies.
Less-attractive sodium vapor lamps should be used near
the home. Self-closing doors in the home will deny
entrance, as will the use of proper-fitting and well-maintained screening on doors and windows.
Larger flies use homes for shelter from the cold, but do
not reproduce inside the home. Caulking entry points
and using fly swatters is effective and much safer than the
use of most pesticides. Insecticide “bombs” can be used in
attics and other rooms that can be isolated from the rest
of the house. However, these should be applied to areas
away from food, where flies rest.
The blowfly is a fairly large, metallic green, gray, blue,
bronze, or black fly. They may spend the winter in homes
or other protected sites, but will not reproduce during
this time. Blowflies breed most commonly on decayed
carcasses (e.g., dead squirrels, rodents, birds) and in droppings of dogs or other pets during the summer; thus,
removal of these sources is imperative. Small animals, on
occasion, may die inside walls or under the crawl space of
a house. A week or two later, blowflies or maggots may
appear. The adult blowfly is also attracted to gas leaks.
Figure 4.17. Life Cycle of the Fly [10]
Termites
According to Gold et al. [11], subterranean termites are
the most destructive insect pests of wood in the United
States, causing more than $2 billion in damage each year.
Annually, this is more property damage than that caused
by fire and windstorms combined. In the natural world,
these insects are beneficial because they break down dead
trees and other wood materials that would otherwise
accumulate. This biomass breakdown is recycled to the
soil as humus. MPMH [2], on the other hand, notes that
these insects can damage a building so severely it may
have to be replaced. Termites consume wood and other
cellulose products, such as paper, cardboard, and fiberboard. They will also destroy structural timbers, pallets,
crates, furniture, and other wood products. In addition,
they will damage many materials they do not normally
eat as they search for food. The tunneling efforts of subterranean termites can penetrate lead- and plastic-covered
electric cable and cause electrical system failure. In
nature, termites may live for years in tree stumps or lumber beneath concrete buildings before they penetrate
hairline cracks in floors and walls, as well as expansion
joints, to search for food in areas such as interior door
frames and immobile furniture. Termite management
costs to homeowners are exceeded only by cockroach
control costs.
Lyon [12] notes that termites are frequently mistaken by
the homeowner as ants and often are referred to erroneously as white ants. Typical signs of termite infestations
occur in March through June and in September and
October. Swarming is an event where a group of adult
males and female reproductives leave the nest to establish
a new colony. If the emergence happens inside a building,
flying termites may constitute a considerable nuisance.
These pests can be collected with a vacuum cleaner or
otherwise disposed of without using pesticides. Each
homeowner should be aware of the following signs of termite infestation:
• Pencil-thin mud tubes extending over the inside and
outside surfaces of foundation walls, piers, sills, joists,
and similar areas (Figures 4.18 and 4.19).
• Presence of winged termites or their shed wings on
windowsills and along the edges of floors.
• Damaged wood hollowed out along the grain and
lined with bits of mud or soil. According to Oi et al.
[15], termite tubes and nests are made of mud and
carton. Carton is composed of partially chewed wood,
feces, and soil packed together. Tubes maintain the
4-9Chapter 4: Disease Vectors and PestsHealthy Housing Reference Manual
to Lyon [12], the reproductives can be winged or wingless, with the latter found in colonies to serve as replacements for the primary reproductives. The primary
reproductives (alates) vary in color from pale yellowbrown to coal black, are ½-inch to 3/8-inch in length, are
flattened dorsa-ventrally, and have pale or smoke-gray to
brown wings. The secondary reproductives have short
wing buds and are white to cream colored. The workers
are the same size as the primary reproductives and are
white to grayish-white, with a yellow-brown head, and are
wingless. In addition, the soldiers resemble workers, in
that they are wingless, but soldiers have large, rectangular,
yellowish, and brown heads with large jaws.
MPMH [2] states there are five families of termites found
in the world, with four of them occurring in the United
States. The families in the United States are
Hodotermitidae (rotten-wood termites), Kalotermitidae
(dry-wood termites), Rhinotermitidae (subterranean
termites) and Termitidae (desert termites). Subterranean
high humidity required for survival, protect termites
from predators, and allow termites to move from one
spot to another.
Differentiating the ant from the dark brown or black termite reproductives can be accomplished by noting the
respective wings and body shape. MPMH [2] states that a
termite has four wings of about equal length and that the
wings are nearly twice as long as the body. By comparison, ant
wings that are only a little longer than the body and the
hind pair is much shorter than the front. Additionally,
ants typically have a narrow waist, with the abdomen
connected to the thorax by a thin petiole. Termites do
not have a narrow or pinched waist. Figure 4.20a and b
demonstrates the differences between the ant and termite.
Entomologists refer to winged ants and termites as alates.
Figure 4.21 shows the life cycle of the termite. In each
colony, there are three castes or forms of individuals
known as reproductives, workers, and soldiers. According
Figure 4.20a. Ant (Elbowed Antennae: Fore Wings Larger Than Hind;
Constricted Waist) [16]
Figure 4.20b. Termite (Beaded Antennae; All Wings Equal) [16]
Figure 4.18. Termite Tube Extending from Ground to Wall [Red
Arrows] [13]
Figure 4.19. Termite Mud Shelter Tube Constructed Over a
Brick Foundation [14]
termites typically work in wood aboveground, but must
have direct contact with the ground to obtain moisture.
Nonsubterranean termites colonize above the ground and
feed on cellulose; however, their life cycles and methods
of attack, and consequently methods of control, are quite
different. Nonsubterranean termites in the United States
are commonly called drywood termites.
Healthy Housing Reference Manual4-10 Chapter 4: Disease Vectors and Pests
In the United States, according to MPMH [2], native
subterranean termites are the most important and the
most common. These termites include the genus
Reticulitermes, occurring primarily in the continental
United States, and the genus Heterotermes, occurring in
the Virgin Islands, Puerto Rico, and the deserts of
California and Arizona. The appearance, habits, and type
of damage they cause are similar. The Formosan termite
(Coptotermes formosanus) is the newest species to become
established in the United States. It is a native of the
Pacific Islands and spread from Hawaii and Asia to the
United States during the 1960s. It is now found along the
Gulf Coast, in California, and in South Carolina, and is
expected to spread to other areas as well. Formosan termites cause greater damage than do native species because
of their more vigorous and aggressive behavior and their
ability to rapidly reproduce, build tubes and tunnels, and
seek out new items to infest. They have also shown more
resistance to some soil pesticides than native species.
Reproductives (swarmers) are larger than native species,
reaching up to 5/8-inch in length, and are yellow to brown
in color. Swarmers have hairy-looking wings and swarm
after dusk, unlike native species, which swarm in the daytime. Formosan soldiers have more oval-shaped heads
than do native species. On top of the head is an opening
that emits a sticky, whitish substance.
Dry-wood termites (Cryptotermes spp.) live entirely in
moderately to extremely dry wood. They require contact
with neither the soil nor any other moisture source and
may invade isolated pieces of furniture, fence posts, utility poles, firewood, and structures. Dry-wood termite colonies are not as large as other species in the United States,
so they can occupy small wooden articles, which are one
way these insects spread to different locations. They are of
major economic importance in southern California,
Figure 4.21. Life Cycle of the Subterranean Termite [17]
Arizona, and along the Gulf Coast. The West Indian drywood termite is a problem in Puerto Rico, the U.S.
Virgin Islands, Hawaii, parts of Florida and Louisiana,
and a number of U.S. Pacific Island territories. Dry-wood
termites are slightly larger than most other species, ranging from ½ inch to 5/8 inch long, and are generally lighter
in color.
Damp-wood termites do not need contact with damp
ground like subterranean termites do, but they do require
higher moisture content in wood. However, once established, these termites may extend into slightly drier wood.
Termites of minor importance are the tree-nesting groups.
The nests of these termites are found in trees, posts, and,
occasionally, buildings. Their aboveground nests are connected to soil by tubes. Tree-nesting termites may be a
problem in Puerto Rico and the U.S. Virgin Islands.
The risk for encountering subterranean termites in the
United States is greater in the southeastern states and in
southwestern California. In the United States, the risk for
termite infestations tends to decrease as the latitude
increases northward.
Figure 4.22 portrays the geographic risk of subterranean
termites in the United States. Subterranean termites are
found in all states except Alaska and are most abundant
in the south and southeastern United States [18].
According to Potter [19], homeowners can reduce the risk
for termite attack by adhering to the following suggestions:
• Eliminate wood contact with the ground. Earth-towood contact provides termites with simultaneous
access to food, moisture, and shelter in conjunction
with direct, hidden entry into the structure. In
addition, the homeowner or occupant should be aware
that pressure-treated wood is not immune to termite
attack because termites can enter through the cut ends
and build tunnels over the surfaces.
• Do not allow moisture to accumulate near the
home’s foundation. Proper drainage, repair of
plumbing, and proper grading will help to reduce the
presence of moisture, which attracts termites.
• Reduce humidity in crawl spaces. Most building
codes state that crawl space area should be vented at a
rate of 1 square foot per 150 square feet of crawl space
area. This rate can be reduced for crawl spaces
equipped with a polyethylene or equivalent vapor
barrier to one square foot per 300 to 500 square feet
of crawl space area. Vent placement design includes
positioning one vent within 3 feet of each building
4-11Chapter 4: Disease Vectors and PestsHealthy Housing Reference Manual
corner. Trimming and controlling shrubs so that they
do not obstruct the vents is imperative. Installling a 4to 6-mil polyethylene sheeting over a minimum of
75% of the crawl space will reduce the crawl-space
moisture. Covering the entire floor of the crawl space
with such material can reduce two potential home
problems at one time: excess moisture and radon
(Chapter 5). The barrier will reduce the absorption of
moisture from the air and the release of moisture into
the air in the crawl space from the underlying soil.
• Never store firewood, lumber, or other wood debris
against the foundation or inside the crawl space.
Termites are both attracted to and fed by this type of
storage. Wood stacked in contact with a dwelling and
vines, trellises, and dense plant material provide a
pathway for termites to bypass soil barrier treatment.
• Use decorative wood chips and mulch sparingly.
Cellulose-containing products attract termites, especially
materials that have moisture-holding properties, such as
mulch. The homeowner should never allow these
products to contact wood components of the home.
The use of crushed stone or pea gravel is recommended
as being less attractive to termites and helpful in
diminishing other pest problems.
Figure 4.22. Subterranean Termite Risk in the United States [18]
• Have the structure treated by a professional pest
control treatment. The final, and most effective,
strategy to prevent infestation is to treat the soil
around and beneath the building with termiticide. The
treated ground is then both a repellant and toxic to
termites.
Figure 4.23 demonstrates some typical points of attack by
subterranean termites and some faulty construction practices
that can contribute to subterranean termite infestations.
Lyon [12] notes the following alternative termite control
measures:
• Nematodes. Certain species of parasitic round worms
(nematodes) will infest and kill termites and other soil
insects. Varying success has been experienced with this
method because it is dependent on several variables,
such as soil moisture and soil type.
• Sand as a physical barrier. This would require
preconstruction planning and would depend on
termites being unable to manipulate the sand to create
tunnels. Some research in California and Hawaii has
indicated early success.
Healthy Housing Reference Manual4-12 Chapter 4: Disease Vectors and Pests
• Chemical baits. This method uses wood or laminated
texture-flavored cellulose impregnated with a toxicant
and/or insect growth regulator. The worker termite
feeds on the substance and carries it back to the nest,
reducing or eliminating the entire colony. According
to HomeReports.com [20], an additional system is to
strategically place a series of baits around the house.
The intention is for termite colonies to encounter one
or more of the baits before approaching the house.
Once termite activity is observed, the bait wood is
replaced with a poison. The termites bring the poison
back to the colony and the colony is either eliminated
or substantially reduced. This system is relatively new
to the market. Its success depends heavily on the
termites finding the bait before finding and damaging
the house.
Additional measures include construction techniques that
discourage termite attacks, as demonstrated in Figure 4.24.
Termites often invade homes by way of the foundation,
either by crawling up the exterior surface where their
activity is usually obvious or by traveling inside hollow
block masonry. One way to deter their activity is to block
their access points on or through the foundation. Metal
termite shields have been used for decades to deter termite movement along foundation walls and piers on up
to the wooden structure. Metal termite shields should
extend 2 inches from the foundation and 2 inches down.
Figure 4.23. Typical Points of Attack by Termites in the Home [2]
Improperly installed (i.e., not soldered/sealed properly),
damaged, or deteriorated termite shields may allow termites to reach parts of the wooden floor system. Shields
should be made of noncorroding metal and have no
cracks or gaps along the seams. If a house is being built
with metal termite shielding, the shielding should extend
at least 2 inches out and 2 inches down at a 45° angle from
the foundation wall. An alternative to using termite
shields on a hollow-block foundation is to fill the block
with concrete or put in a few courses of solid or concretefilled brick (which is often done anyway to level foundations). These are referred to as masonry caps. The same
approach can be used with support piers in the crawl
space. Solid caps (i.e., a continuously poured concrete
cap) are best at stopping termites, but are not commonly
used. Concrete-filled brick caps should deter termite
movement or force them through small gaps, thus allowing them to be spotted during an inspection [21].
Fire Ants
According to MPMH [2], ants are one of the most
numerous species on earth. Ants are in the same order as
wasps and bees and, because of their geographic distribution, they are universally recognized (Figure 4.25).
The life cycle of the fire ant begins with the mating of the
winged forms (alates) some 300 to 800 feet in the air,
typically occurring in the late spring or early summer.
4-13Chapter 4: Disease Vectors and PestsHealthy Housing Reference Manual
The male dies after the mating; and the newly mated
queen finds a suitable moist site, drops her wings, and
burrows in the soil, sealing the opening behind her. Ants
undergo complete metamorphosis and, therefore, have
egg, larval, pupal and adult stages. The new queen will
begin laying eggs within 24 hours. Once fully developed,
she will produce approximately 1,600 eggs per day over a
maximum life span of 7 years. Soft, whitish, legless larvae
are produced from the hatching. These larvae are fed by
the worker ants. Pupae resemble adults in form, but are
soft, nonpigmented, and lack mobility. There are at least
three distinct castes of ants: workers, queens, and males.
Typically, the males have wings, which they retain until
death. Queens, the largest of the three castes, normally
have wings, but lose them after mating. The worker,
which is also a female, is never winged, except as a rare
abnormality. Within this hierarchy, mature colonies contain males and females that are capable of flight and
reproduction. These are known as reproductives, and an
average colony may produce approximately 4,500 of these
per year. A healthy nest usually produces two nuptial
flights of reproductives each year and a healthy, mature
colony may contain more than 250,000 ants. Though
uncommon among ants, multiple queen colonies (10 to
1. Cracks in foundation permit hidden points of entry
from soil to sill.
2. Posts through concrete in contact with substructural
soil. Watch door frames and intermediate supporting
posts.
3. Wood-framing members in contact with earthfill under
concrete slab.
4. Form boards left in place contribute to termite food
supply.
5. Leaking pipes and dripping faucets sustain soil moisture. Excess irrigation has same effect.
6. Shrubbery blocking air flow through vents.
7. Debris supports termite colony until large population
attacks superstructure.
8. Heating unit accelerates termite development by maintaining warmth of colony on a year-round basis.
9. Foundation wall too low permits wood to contact
soil. Adding topsoil often builds exterior grade up to
sill level.
10. Footing too low or soil thrown against it causes woodsoil contact. There should be 8 inches of clean concrete
between soil and pier block.
11. Stucco carried down over concrete foundation permits
hid den entrance between stucco and foundation if
bond fails.
12. Insufficient clearance for inspection also permits easy
construction of termite shelter tubes from soil to wood.
13. Wood framing of crawl hole forming wood-soil contact.
14. Mud sill and/or posts in contact with soil.
15. Wood siding and skirting form soil contact. There
should be a minimum of 3 inches clearance between
skirting and soil.
16. Porch steps in contact with soil. Also watch for ladders
and other wooden materials.
17. Downspouts should carry water away from
the building.
18. Improper maintenance of soil piled against pier footing.
Also makes careful inspection impossible.
19. Wall girder entering recess and foundation wall. Should
have a 1-inch free air space on both sides and end and
be protected with a moisture-impervious seal.
20. Vents placed between joists tunnel air through space
without providing good substructural aeration. Vents
placed in foundation wall give better air circulation.
Key to Figure 4.23
100) occur somewhat frequently in fire ants, resulting in
more numerous mounds per acre.
There are many species of fire ants in the United States.
The most important are four species in the genus
Solenopsis. Of these, the number one fire ant pest is the
red imported fire ant (RIFA) Solenopsis invicta (Figure
4.25). This ant was imported inadvertently from South
America in the 1930s through the port of Mobile,
Alabama. RIFAs are now found in more than 275 million
acres in 11 southern states and Puerto Rico. The second
most important species is the black imported fire ant, S.
richteri, which was introduced into the United States in
the 1920s from Argentina or Uruguay. It is currently limited in distribution to a small area of northern
Mississippi and Alabama. There are two native species
of fire ants: the tropical or native fire ant, S. geminata,
ranging from South Carolina to Florida and west to
Texas; and the Southern fire ant, S. xyloni, which occurs
from North Carolina south to northern Florida, along the
Gulf Coast, and west to California. The most important
extension of the RIFA range is thought to have occurred
during the 1950s housing boom as a result of the transportation of sod and nursery plants (Figure 4.26).
Healthy Housing Reference Manual4-14 Chapter 4: Disease Vectors and Pests
RIFAs prefer open and sun-exposed areas. They are found
in cultivated fields, cemeteries, parks, and yards, and even
inside cars, trucks, and recreational vehicles. RIFAs are
attracted to electrical currents and are known to nest in
and around heat pumps, junction boxes, and similar
areas. They are omnivorous; thus they will attack most
things, living or dead. Their economic effects are felt by
their destruction of the seeds, fruit, shoots, and seedlings
of numerous native plant species. Fire ants are known to
tend pests, such as scale insects, mealy bugs, and aphids,
for feeding on their sweet waste excretion (honeydew).
Figure 4.24. Construction Techniques That Discourage Termite Attacks: Thin Metal Termite Shield Should Extend 2 Inches Beyond Foundation and 2
Inches Down [2]
Figure 4.25. Fire Ants [22]
RIFAs transport these insects to new feeding sites and
protect them from predators. The positive side of RIFA
infestation is that the fire ant is a predator of ticks and
controls the ground stage of horn flies.
The urban dweller with a RIFA infestation may find significant damage to landscape plants, with reductions in
the number of wild birds and mammals. RIFAs can discourage outdoor activities and be a threat to young animals or small confined pets. RIFA nests typically are not
found indoors, but around homes, roadways, and structures, as well as under sidewalks. Shifting of soil after
RIFAs abandon sites has resulted in collapsing structures.
Figure 4.27 shows a fire ant mound with fire ants and a
measure of their relative size.
The medical complications of fire ant stings have been
noted in the literature since 1957. People with disabilities,
reduced feeling in their feet and legs, young children, and
those with mobility issues are at risk for sustaining
numerous stings before escaping or receiving assistance.
Fatalities have resulted from attacks on the elderly and on
infants. Control of the fire ant is primarily focused on the
mound by using attractant bait consisting of soybean oil,
corn grits, or chemical agents. The bait is picked up by
the worker ants and taken deep into the mound to the
queen. These products typically require weeks to work.
Individual mound treatment is usually most effective in
the spring. The key is to locate and treat all mounds in
4-15Chapter 4: Disease Vectors and PestsHealthy Housing Reference Manual
the area to be protected. If young mounds are missed, the
area can become reinfested in less than a year.
Mosquitoes
All mosquitoes have four stages of development— egg,
larva, pupa, and adult— and spend their larval and pupal
stages in water. The females of some mosquito species
deposit eggs on moist surfaces, such as mud or fallen
leaves, that may be near water but dry. Later, rain or high
tides reflood these surfaces and stimulate the eggs to
hatch into larvae. The females of other species deposit
their eggs directly on the surface of still water in such
places as ditches, street catch basins, tire tracks, streams
that are drying up, and fields or excavations that hold
water for some time. This water is often stagnant and
close to the home in discarded tires, ornamental pools,
unused wading and swimming pools, tin cans, bird baths,
plant saucers, and even gutters and flat roofs. The eggs
soon hatch into larvae. In the hot summer months, larvae
grow rapidly, become pupae, and emerge 1 week later as
flying adult mosquitoes. A few important spring species
have only one generation per year. However, most species
have many generations per year, and their rapid increase
in numbers becomes a problem.
When adult mosquitoes emerge from the aquatic stages,
they mate, and the female seeks a blood meal to obtain
Figure 4.26. Range Expansion of Red Imported Fire Ants [RIFAs] in the United States, 1918–1998 [23]
Figure 4.27. Fire Ant Mound
Source: CAPT Craig Shepherd, U.S. PHS; used with permission.
the protein necessary for the development of her eggs.
The females of a few species may produce a first batch of
eggs without this first blood meal. After a blood meal is
digested and the eggs are laid, the female mosquito again
seeks a blood meal to produce a second batch of eggs.
Depending on her stamina and the weather, she may
repeat this process many times without mating again. The
male mosquito does not take a blood meal, but may feed
on plant nectar. He lives for only a short time after mating. Most mosquito species survive the winter, or overwinter, in the egg stage, awaiting the spring thaw, when
Healthy Housing Reference Manual4-16 Chapter 4: Disease Vectors and Pests
waters warm and the eggs hatch. A few important species
spend the winter as adult, mated females, resting in protected, cool locations, such as cellars, sewers, crawl spaces,
and well pits. With warm spring days, these females seek
a blood meal and begin the cycle again. Only a few species can overwinter as larvae.
Mosquitoborne diseases, such as malaria and yellow fever,
have plagued civilization for thousands of years. Newer threats
include Lyme disease and West Nile virus. Organized mosquito
control in the United States has greatly reduced the incidence of these diseases. However, mosquitoes can still
transmit a few diseases, including eastern equine encephalitis
and St. Louis encephalitis. The frequency and extent of
these diseases depend on a complex series of factors.
Mosquito control agencies and health departments cooperate
in being aware of these factors and reducing the chance
for disease. It is important to recognize that young adult
female mosquitoes taking their first blood meal do not
transmit diseases. It is instead the older females, who, if they
have picked up a disease organism in their first blood meals,
can then transmit the disease during the second blood meal.
The proper method to manage the mosquito problem in
a community is through an organized integrated pest management system that includes all approaches that safely manage the problem. The spraying of toxic agents is but one of
many approaches.
When mosquitoes are numerous and interfere with living,
recreation, and work, you can use the various measures
described in the following paragraphs to reduce their
annoyance, depending on location and conditions.
How to Reduce the Mosquito Population
The most efficient method of controlling mosquitoes is
by reducing the availability of water suitable for larval
and pupal growth. Large lakes, ponds, and streams that have
waves, contain mosquito-eating fish, and lack aquatic vegetation around their edges do not contain mosquitoes;
mosquitoes thrive in smaller bodies of water in protected
places. Examine your home and neighborhood and take the
following precautions recommended by the New Jersey
Agricultural Experiment Station [24]:
• dispose of unwanted tin cans and tires;
• clean clogged roof gutters and drain flat roofs;
• turn over unused wading pools and other containers
that tend to collect rainwater;
• change water in birdbaths, fountains, and troughs
twice a week;
• clean and chlorinate swimming pools;
• cover containers tightly with window screen or plastic
when storing rainwater for garden use during drought
periods;
• flush sump-pump pits weekly; and
• stock ornamental pools with fish.
If mosquito breeding is extensive in areas such as woodland
pools or roadside ditches, the problem may be too great
for individual residents. In such cases, call the organized
mosquito control agency in your area. These agencies
have highly trained personnel who can deal with the
problem effectively.
Several commercially available insecticides can be effective
in controlling larval and adult mosquitoes. These chemicals
are considered sufficiently safe for use by the public.
Select a product whose label states that the material is
effective against mosquito larvae or adults. For safe and
effective use, read the label and follow the instructions for
applying the material. The label lists those insects that the
EPA agrees are effectively controlled by the product.
For use against adult mosquitoes, some liquid insecticides
can be mixed according to direction and sprayed lightly
on building foundations, hedges, low shrubbery, ground
covers, and grasses. Do not overapply liquid insecticides—
excess spray drips from the sprayed surfaces to the ground,
where it is ineffective. The purpose of such sprays is to
leave a fine deposit of insecticide on surfaces where mosquitoes
rest. Such sprays are not effective for more than 1 or 2 days.
Some insecticides are available as premixed products or
aerosol cans. These devices spray the insecticide as very
small aerosol droplets that remain floating in the air and
hit the flying mosquitoes. Apply the sprays upwind, so
the droplets drift through the area where mosquito control is desired. Rather than applying too much of these
aerosols initially, it is more practical to apply them briefly
but periodically, thereby eliminating those mosquitoes
that recently flew into the area.
Various commercially available repellents can be purchased as a cream or lotion or in pressurized cans, then
applied to the skin and clothing. Some manufacturers also
offer clothing impregnated with repellents; coarse, repellent-bearing particles to be scattered on the ground; and
candles whose wicks can be lit to release a repellent chemical. The effectiveness of all repellents varies from location
to location, from person to person, and from mosquito to
mosquito. Repellents can be especially effective in recreation areas, where mosquito control may not be con4-17Chapter 4: Disease Vectors and PestsHealthy Housing Reference Manual
ducted. All repellents should be used according to the
manufacturers’ instructions. Mosquitoes are attracted by
perspiration, warmth, body odor, carbon dioxide, and
light. Mosquito control agencies use some of these attractants to help determine the relative number of adult mosquitoes in an area. Several devices are sold that are
supposed to attract, trap, and destroy mosquitoes and
other flying insects. However, if these devices are attractive to mosquitoes, they probably attract more mosquitoes into the area and may, therefore, increase rather than
decrease mosquito annoyance.
References
1. Barnett DB. Vectors and their control. In: Morgan MT,
editor. Environmental health. 3rd ed. Englewood, CO:
Wadsworth Publishing Co.; 2002. p. 137–50.
2. Armed Forces Pest Management Board. Military pest
management handbook. Washington, DC: Armed Forces
Pest Management Board; no date. Available from URL:
http://www.afpmb.org/ MPMH/toc.htm.
3. Indiana Department of Natural Resources. Rodent
pictures. Lafayette, IN: Indiana Department of Natural
Resources; no date. Available from URL: http://www.
entm.purdue.edu/ wildlife/rat_pictures.htm.
4. Arrow Services, Inc. Rats: roof rats. Plymouth, IN: Arrow
Services, Inc.; no date. Available from URL: http://www.
arrowpestcontrol.com/pages/rod/roofpic.html.
5. Cobb County Extension Service. Fact sheet on rodents:
rats and mice. Marietta, GA: Cobb County Extension
Service; 2003. Available from URL: http://www.griffin.
peachnet.edu/ga/cobb/Horticulture/Factsheets/
peskycritters/ratsmice.htm.
6. Kamble ST, Keith DL. Cockroaches and their control.
Lincoln, NE: University of Nebraska Cooperative
Extension; 1995.
7. University of Nebraska-Lincoln. Cockroach picture gallery.
Lincoln, NE: University of Nebraska-Lincoln; no date.
Available from URL: http://pested.unl.edu/roachind.htm.
8. Centers for Disease Control and Prevention. Reported
human plague cases by county: United States, 1970–1997.
Atlanta: US Department of Health and Human Services;
no date. Available from URL: http://www.cdc.gov/ncidod/
dvbid/plague/plagwest.htm.
9. Leslie M, editor. Netwatch: flys in the Web. Science
2004;306:1269. Available from URL: http://www.sel.barc.
usda.gov/diptera/names/images/ science1104.pdf.
10. Oderkirk A. Fly control in poultry barns: poultry fact
sheet. Truro, Nova Scotia, Canada: Nova Scotia
Department of Agriculture and Marketing; 2001.
11. Gold RE, Howell HN Jr, Glenn GJ. Subterranean
termites. College Station, TX: Texas Agricultural
Extension Service; 1999. Available from URL:
http://insects.tamu.edu/extension/bulletins/b6080.html.
12. Lyon WF. Termite control: HYG-2092-03. Columbus,
OH: The Ohio State University Extension; 2003.
Available from URL: http://ohioline.osu.edu/
hyg-fact/2000/2092.html.
13. Austin AR. Sample photos of structural foundation defects
and deficiences. Houston: Diligent Home Inspections; no
date.
14. Fumapest Group. Western subterranean termites. Revesby,
New South Wales, Australia: Fumapest Group Pty.; no
date. Available from URL: http://www.termite.com/
termites/western-subterranean-termite.html.
15. Oi FM, Castner JL, Koehler PG. The Eastern
subterranean termite. Gainesville, FL: University of Florida
Cooperative Extension Service; 1997. Available from
URL: http://edis.ifas.ufl.edu/BODY_IN031.
16. Ferster B, Deyrup M, Scheffrahn RH. How to tell the
difference between ant and termite alates. Fort Lauderdale,
FL: University of Florida; no date. Available from URL:
http://flrec.ifas.ufl.edu/entomo/ants/
Ant%20vs%20Termite.htm.
17. Su N-Y. Life cycle of the Formosan subterranean termite,
Coptotermes formosanus Shiraki. Gainesville, FL: University
of Florida; no date. Available from URL: http://creatures.
ifas.ufl.edu/urban/termites/fst10.htm.
18. Suiter DR, Jones SC, Forschler BT. Biology of
subterranean termites in the Eastern United States.
Bulletin 1209. Columbus, OH: The Ohio State
University Extension; no date. Available from URL:
http://ohioline.osu.edu/b1209/.
19. Potter MF. Protecting your home against termites.
Lexington, KY: University of Kentucky Department of
Entomology; 2004. Available from URL: http://www.uky.
edu/Agriculture/Entomology/entfacts/struct/ef605.htm.
20. HomeReports.com. Pest and termite control companies.
Atlanta: HomeReports.com; no date. Available from
URL: http://www.homereports.com/ge/ PestControl.htm.
21. North Carolina Cooperative Extension Service. Termite
prevention: approaches for new construction. Raleigh,
Healthy Housing Reference Manual4-18 Chapter 4: Disease Vectors and Pests
NC: North Carolina Cooperative Extension Service; no
date. Available from URL: http://www.ces.ncsu.edu/depts/
ent/notes/Urban/termites/pre-con.htm.
22. Core J. Update: hot on the trail of fire ants. Agric Res
2003; 51:20-23. Available from URL: http://ars.usda. gov/
is/AR/archive/Feb03/ants0203.htm.
23. California Department of Food and Agriculture. First
reported occurrence of red imported fire ant; Solenopsis
invicta. Sacramento, CA: California Department of Food
and Agriculture; no date. Available from URL: www.cdfa.
ca.gov/phpps/pdep/rifa/html/english/facts/rifaTIME.htm.
24. Sutherland DJ, Crans WJ. Mosquitoes in your life. New
Jersey Agricultural Experiment Station Publication
SA220-5M-86. New Brunswick, NJ: New Jersey
Agricultural Experiment Station, Cook College, Rutgers,
The State University of New Jersey; no date. Available at
URL: http://www.rci.rutgers.edu/~insects/moslife.htm.
5-1Chapter 5: Indoor Air Pollutants and Toxic MaterialsHealthy Housing Reference Manual
“Walking into a modern building can sometimes be compared to placing your head inside a plastic bag that is filled
with toxic fumes.”
John Bower
Founder, Healthy House Institute
Introduction
We all face a variety of risks to our health as we go about
our day-to-day lives. Driving in cars, flying in airplanes,
engaging in recreational activities, and being exposed to
environmental pollutants all pose varying degrees of risk.
Some risks are simply unavoidable. Some we choose to
accept because to do otherwise would restrict our ability
to lead our lives the way we want. Some are risks we
might decide to avoid if we had the opportunity to make
informed choices. Indoor air pollution and exposure to
hazardous substances in the home are risks we can do
something about.
In the last several years, a growing body of scientific evidence has indicated that the air within homes and other
buildings can be more seriously polluted than the outdoor air in even the largest and most industrialized cities.
Other research indicates that people spend approximately
90% of their time indoors. Thus, for many people, the
risks to health from exposure to indoor air pollution may
be greater than risks from outdoor pollution.
In addition, people exposed to indoor air pollutants for
the longest periods are often those most susceptible to
their effects. Such groups include the young, the elderly,
and the chronically ill, especially those suffering from
respiratory or cardiovascular disease [1].
Indoor Air Pollution
Numerous forms of indoor air pollution are possible in
the modern home. Air pollutant levels in the home
increase if not enough outdoor air is brought in to dilute
emissions from indoor sources and to carry indoor air
pollutants out of the home. In addition, high temperature and humidity levels can increase the concentration of
some pollutants. Indoor pollutants can be placed into
two groups, biologic and chemical.
Biologic Pollutants
Biologic pollutants include bacteria, molds, viruses, animal dander, cat saliva, dust mites, cockroaches, and pollen. These biologic pollutants can be related to some
Chapter 5: Indoor Air Pollutants and Toxic Materials
serious health effects. Some biologic pollutants, such as
measles, chickenpox, and influenza are transmitted
through the air. However, the first two are now preventable with vaccines. Influenza virus transmission, although
vaccines have been developed, still remains of concern in
crowded indoor conditions and can be affected by ventilation levels in the home.
Common pollutants, such as pollen, originate from plants
and can elicit symptoms such as sneezing, watery eyes,
coughing, shortness of breath, dizziness, lethargy, fever,
and digestive problems. Allergic reactions are the result of
repeated exposure and immunologic sensitization to particular biologic allergens.
Although pollen allergies can be bothersome, asthmatic
responses to pollutants can be life threatening. Asthma is
a chronic disease of the airways that causes recurrent and
distressing episodes of wheezing, breathlessness, chest
tightness, and coughing [2]. Asthma can be broken down
into two groups based on the causes of an attack: extrinsic (allergic) and intrinsic (nonallergic). Most people with
asthma do not fall neatly into either type, but somewhere
in between, displaying characteristics of both classifications. Extrinsic asthma has a known cause, such as allergies to dust mites, various pollens, grass or weeds, or pet
danders. Individuals with extrinsic asthma produce an
excess amount of antibodies when exposed to triggers.
Intrinsic asthma has a known cause, but the connection
between the cause and the symptoms is not clearly understood. There is no antibody hypersensitivity in intrinsic
asthma. Intrinsic asthma usually starts in adulthood without a strong family history of asthma. Some of the known
triggers of intrinsic asthma are infections, such as cold
and flu viruses, exercise and cold air, industrial and occupational pollutants, food additives and preservatives,
drugs such as aspirin, and emotional stress. Asthma is
more common in children than in adults, with nearly 1
of every 13 school-age children having asthma [3]. Lowincome African-Americans and certain Hispanic populations suffer disproportionately, with urban inner cities
having particularly severe problems. The impact on
neighborhoods, school systems, and health care facilities
from asthma is severe because one-third of all pediatric
emergency room visits are due to asthma, and it is the
fourth most prominent cause of physician office visits.
Additionally, it is the leading cause of school absenteeism— 14 million school days lost each year— from
chronic illness [4]. The U.S. population, on the average,
Healthy Housing Reference Manual5-2 Chapter 5: Indoor Air Pollutants and Toxic Materials
spends as much as 90% of its time indoors. Consquently,
allergens and irritants from the indoor environment may
play a significant role in triggering asthma episodes. A
number of indoor environmental asthma triggers are biologic pollutants. These can include rodents (discussed in
Chapter 4), cockroaches, mites, and mold.
Cockroaches
The droppings, body parts, and saliva of cockroaches can
be asthma triggers. Cockroaches are commonly found in
crowded cities and in the southern United States.
Allergens contained in the feces and saliva of cockroaches
can cause allergic reactions or trigger asthma symptoms.
A national study by Crain et al. [5] of 994 inner-city
allergic children from seven U.S. cities revealed that
cockroaches were reported in 58% of the homes. The
Community Environmental Health Resource Center
reports that cockroach debris, such as body parts and old
shells, trigger asthma attacks in individuals who are
sensitized to cockroach allergen [6]. Special attention to
cleaning must be a priority after eliminating the presence
of cockroaches to get rid of the presence of any allergens left
that can be asthma triggers.
House Dust Mites
Another group of arthropods linked to asthma is house
dust mites. In 1921, a link was suggested between
asthmatic symptoms and house dust, but it was not until
1964 that investigators suggested that a mite could be
responsible. Further investigation linked a number of mite
species to the allergen response and revealed that humid
homes have more mites and, subsequently, more
allergens. In addition, researchers established that fecal
pellets deposited by the mites accumulated in home
fabrics and could become airborne via domestic activities
such as vacuuming and dusting, resulting in inhalation by
the inhabitants of the home. House dust mites are
distributed worldwide, with a minimum of 13 species
identified from house dust. The two most common in
the United States are the North American house dust
mite (Dermatophagoides farinae) and the European house
dust mite (D. pteronyssinus). According to Lyon [7], house
dust mites thrive in homes that provide a source of food
and shelter and adequate humidity. Mites prefer relative
humidity levels of 70% to 80% and temperatures of 75°F
to 80°F (24°C to 27°C). Most mites are found in
bedrooms in bedding, where they spend up to a third of
their lives. A typical used mattress may have from
100,000 to 10 million mites in it. In addition, carpeted
floors, especially long, loose pile carpet, provide a
microhabitat for the accumulation of food and moisture
for the mite, and also provide protection from removal by
vacuuming. The house dust mite’s favorite food is human
dander (skin flakes), which are shed at a rate of
approximately 0.20 ounces per week.
A good microscope and a trained observer are imperative
in detecting mites. House dust mites also can be detected
using diagnostic tests that measure the presence and
infestation level of mites by combining dust samples
collected from various places inside the home with
indicator reagents [7]. Assuming the presence of mites,
the precautions listed below should be taken if people
with asthma are present in the home:
• Use synthetic rather than feather and down pillows.
• Use an approved allergen barrier cover to enclose the
top and sides of mattresses and pillows and the base of
the bed.
• Use a damp cloth to dust the plastic mattress cover
daily.
• Change bedding and vacuum the bed base and
mattress weekly.
• Use nylon or cotton cellulose blankets rather than
wool blankets.
• Use hot (120°F–130°F [49°C–54°C]) water to wash all
bedding, as well as room curtains.
• Eliminate or reduce fabric wall hangings, curtains, and
drapes.
• Use wood, tile, linoleum, or vinyl floor covering rather
than carpet. If carpet is present, vacuum regularly with
a high-efficiency particulate air (HEPA) vacuum or a
household vacuum with a microfiltration bag.
• Purchase stuffed toys that are machine washable.
• Use fitted sheets to help reduce the accumulation of
human skin on the mattress surface.
HEPA vacuums are now widely available and have also
been shown to be effective [8]. A conventional vacuum
tends to be inefficient as a control measure and results in
a significant increase in airborne dust concentrations, but
can be used with multilayer microfiltration collection
bags. Another approach to mite control is reducing
indoor humidity to below 50% and installing central
air conditioning.
Two products are available to treat house dust mites and
their allergens. These products contain the active
ingredients benzyl benzoate and tannic acid.
5-3Chapter 5: Indoor Air Pollutants and Toxic MaterialsHealthy Housing Reference Manual
Pets
According to the U.S. Environmental Protection Agency
(EPA) [9], pets can be significant asthma triggers because
of dead skin flakes, urine, feces, saliva, and hair. Proteins
in the dander, urine, or saliva of warm-blooded animals
can sensitize individuals and lead to allergic reactions or
trigger asthmatic episodes. Warm-blooded animals include
dogs, cats, birds, and rodents (hamsters, guinea pigs,
gerbils, rats, and mice). Numerous strategies, such as the
following, can diminish or eliminate animal allergens in
the home:
• Eliminate animals from the home.
• Thoroughly clean the home (including floors and
walls) after animal removal.
• If pets must remain in the home, reduce pet exposure
in sleeping areas. Keep pets away from upholstered
furniture, carpeted areas, and stuffed toys, and keep the
pets outdoors as much as possible.
However, there is some evidence that pets introduced early
into the home may prevent asthma. Several studies have
shown that exposure to dogs and cats in the first year of
life decreases a child’s chances of developing allergies [10]
and that exposure to cats significantly decreases sensitivity
to cats in adulthood [11]. Many other studies have shown
a decrease in allergies and asthma among children who
grew up on a farm and were around many animals [12].
Mold
People are routinely exposed to more than 200 species of
fungi indoors and outdoors [13]. These include moldlike
fungi, as well as other fungi such as yeasts and mushrooms. The terms “mold” and “mildew” are nontechnical
names commonly used to refer to any fungus that is growing in the indoor environment. Mold colonies may appear
cottony, velvety, granular, or leathery, and may be white,
gray, black, brown, yellow, greenish, or other colors. Many
reproduce via the production and dispersion of spores.
They usually feed on dead organic matter and, provided
with sufficient moisture, can live off of many materials
found in homes, such as wood, cellulose in the paper
backing on drywall, insulation, wallpaper, glues used to
bond carpet to its backing, and everyday dust and dirt.
Certain molds can cause a variety of adverse human
health effects, including allergic reactions and immune
responses (e.g., asthma), infectious disease (e.g., histoplasmosis), and toxic effects (e.g., aflatoxin-induced liver cancer from exposure to this mold-produced toxin in food)
[14]. A recent Institute of Medicine (IOM) review of the
scientific literature found sufficient evidence for an association between exposure to mold or other agents in damp
indoor environments and the following conditions: upper
respiratory tract symptoms, cough, wheeze, hypersensitivity pneumonitis in susceptible persons, and asthma symptoms in sensitized persons [15]. A previous scientific
review was more specific in concluding that sufficient evidence exists to support associations between fungal allergen exposure and asthma exacerbation and upper
respiratory disease [13]. Finally, mold toxins can cause
direct lung damage leading to pulmonary diseases other
than asthma [13].
The topic of residential mold has received increasing public and media attention over the past decade. Many news
stories have focused on problems associated with “toxic
mold” or “black mold,” which is often a reference to the
toxin-producing mold, Stachybotrys chartarum. This
might give the impression that mold problems in homes
are more frequent now than in past years; however, no
good evidence supports this. Reasons for the increasing
attention to this issue include high-visibility lawsuits
brought by property owners against builders and developers, scientific controversies regarding the degree to which
specific illness outbreaks are mold-induced, and an
increase in the cost of homeowner insurance policies due
to the increasing number of mold-related claims. Modern
construction might be more vulnerable to mold problems
because tighter construction makes it more difficult for
internally generated water vapor to escape, as well as the
widespread use of paper-backed drywall in construction
(paper is an excellent medium for mold growth when
wet), and the widespread use of carpeting.
Allergic Health Effects. Many molds produce numerous
protein or glycoprotein allergens capable of causing allergic reactions in people. These allergens have been measured in spores as well as in other fungal fragments. An
estimated 6%–10% of the general population and 15%–
50% of those who are genetically susceptible are sensitized to mold allergens [13]. Fifty percent of the 937
children tested in a large multicity asthma study sponsored by the National Institutes of Health showed sensitivity to mold, indicating the importance of mold as an
asthma trigger among these children [16]. Molds are
thought to play a role in asthma in several ways. Molds
produce many potentially allergenic compounds, and
molds may play a role in asthma via release of irritants
that increase potential for sensitization or release of toxins
(mycotoxins) that affect immune response [13].
Toxics and Irritants. Many molds also produce mycotoxins that can be a health hazard on ingestion, dermal contact, or inhalation [14]. Although common outdoor
Healthy Housing Reference Manual5-4 Chapter 5: Indoor Air Pollutants and Toxic Materials
molds present in ambient air, such as Cladosporium cladosporioides and Alternaria alternata, do not usually produce
toxins, many other different mold species do [17].
Genera-producing fungi associated with wet buildings,
such as Aspergillus versicolor, Fusarium verticillioides,
Penicillium aiurantiorisen, and S. chartarum, can produce
potent toxins [17]. A single mold species may produce
several different toxins, and a given mycotoxin may be
produced by more than one species of fungi.
Furthermore, toxin-producing fungi do not necessarily
produce mycotoxins under all growth conditions, with
production being dependent on the substrate it is metabolizing, temperature, water content, and humidity [17].
Because species of toxin-producing molds generally have
a higher water requirement than do common household
molds, they tend to thrive only under conditions of
chronic and severe water damage [18]. For example,
Stachybotrys typically only grows under continuously wet
conditions [19]. It has been suggested that very young
children may be especially vulnerable to certain mycotoxins [19,20]. For example, associations have been reported
for pulmonary hemorrhage (bleeding lung) deaths in
infants and the presence of S. chartarum [21–24].
Causes of Mold. Mold growth can be caused by any condition resulting in excess moisture. Common moisture
sources include rain leaks (e.g., on roofs and wall joints);
surface and groundwater leaks (e.g., poorly designed or
clogged rain gutters and footing drains, basement leaks);
plumbing leaks; and stagnant water in appliances (e.g.,
dehumidifiers, dishwashers, refrigerator drip pans, and
condensing coils and drip pans in HVAC systems).
Moisture problems can also be due to water vapor migration and condensation problems, including uneven
indoor temperatures, poor air circulation, soil air entry
into basements, contact of humid unconditioned air with
cooled interior surfaces, and poor insulation on indoor
chilled surfaces (e.g., chilled water lines). Problems can
also be caused by the production of excess moisture
within homes from humidifiers, unvented clothes dryers,
overcrowding, etc. Finished basements are particularly
susceptible to mold problems caused by the combination
of poorly controlled moisture and mold-supporting materials (e.g., carpet, paper-backed sheetrock) [15]. There is
also some evidence that mold spores from damp or wet
crawl spaces can be transported through air currents into
the upper living quarters. Older, substandard housing low
income families can be particularly prone to mold problems because of inadequate maintenance (e.g., inoperable
gutters, basement and roof leaks), overcrowding, inadequate insulation, lack of air conditioning, and poor heating. Low interior temperatures (e.g., when one or two
rooms are left unheated) result in an increase in the relative humidity, increasing the potential for water to condense on cold surfaces.
Mold Assessment Methods. Mold growth or the potential for mold growth can be detected by visual inspection
for active or past microbial growth, detection of musty
odors, and inspection for water staining or damage. If it is
not possible or practical to inspect a residence, this information can be obtained using occupant questionnaires.
Visual observation of mold growth, however, is limited by
the fact that fungal elements such as spores are microscopic, and that their presence is often not apparent until
growth is extensive and the fact that growth can occur in
hidden spaces (e.g., wall cavities, air ducts).
Portable, hand-held moisture meters, for the direct measurement of moisture levels in materials, may also be useful in qualitative home assessments to aid in pinpointing
areas of potential biologic growth that may not otherwise
be obvious during a visual inspection [14].
For routine assessments in which the goal is to identify
possible mold contamination problems before remediation, it is usually unnecessary to collect and analyze air or
settled dust samples for mold analysis because decisions
about appropriate intervention strategies can typically be
made on the basis of a visual inspection [25]. Also, sampling and analysis costs can be relatively high and the
interpretation of results is not straightforward. Air and
dust monitoring may, however, be necessary in certain situations, including 1) if an individual has been diagnosed
with a disease associated with fungal exposure through
inhalation, 2) if it is suspected that the ventilation systems
are contaminated, or 3) if the presence of mold is suspected but cannot be identified by a visual inspection or
bulk sampling [26]. Generally, indoor environments contain large reservoirs of mold spores in settled dust and
contaminated building materials, of which only a relatively small amount is airborne at a given time.
Common methods for sampling for mold growth include
bulk sampling techniques, air sampling, and collection of
settled dust samples. In bulk sampling, portions of materials with visual or suspected mold growth (e.g., sections
of wallboard, pieces of duct lining, carpet segments, or
return air filters) are collected and directly examined to
determine if mold is growing and to identify the mold
species or groups that are present. Surface sampling in
mold contamination investigations may also be used when
a less destructive technique than bulk sampling is desired.
For example, nondestructive samples of mold may be collected using a simple swab or adhesive tape [14].
5-5Chapter 5: Indoor Air Pollutants and Toxic MaterialsHealthy Housing Reference Manual
Air can also be sampled for mold using pumps that pull
air across a filter medium, which traps airborne mold
spores and fragments. It is generally recommended that
outdoor air samples are collected concurrent with indoor
samples for comparison purposes for measurement of
baseline ambient air conditions. Indoor contamination
can be indicated by indoor mold distributions (both species and concentrations) that differ significantly from the
distributions in outdoor samples [14]. Captured mold
spores can be examined under a microscope to identify
the mold species/groups and determine concentrations or
they can be cultured on growth media and the resulting
colonies counted and identified. Both techniques require
considerable expertise.
Dust sampling involves the collection of settled dust samples (e.g., floor dust) using a vacuum method in which
the dust is collected onto a porous filter medium or into
a container. The dust is then processed in the laboratory
and the mold identified by culturing viable spores.
Mold Standards. No standard numeric guidelines exist
for assessing whether mold contamination exists in an
area. In the United States, no EPA regulations or standards exist for airborne mold contaminants [26]. Various
governmental and private organizations have, however,
proposed guidance on the interpretation of fungal measures of environmental media in indoor environments
(quantitative limits for fungal concentrations).
Given evidence that young children may be especially
vulnerable to certain mycotoxins [18] and in view of the
potential severity or diseases associated with mycotoxin
exposure, some organizations support a precautionary
approach to limiting mold exposure [19]. For example,
the American Academy of Pediatrics recommends that
infants under 1 year of age are not exposed at all to
chronically moldy, water-damaged environments [18].
Mold Mitigation. Common intervention methods for
addressing mold problems include the following:
• maintaining heating, ventilating, and air conditioning
(HVAC) systems;
• changing HVAC filters frequently, as recommended by
manufacturer;
• keeping gutters and downspouts in working order and
ensuring that they drain water away from the
foundation;
• routinely checking, cleaning, and drying drip pans in
air conditioners, refrigerators, and dehumidifiers;
• increasing ventilation (e.g., using exhaust fans or open
windows to remove humidity when cooking,
showering, or using the dishwasher);
• venting clothes dryers to the outside; and
• maintaining an ideal relative humidity level in the
home of 40% to 60%.
• locating and removing sources of moisture (controlling
dampness and humidity and repairing water leakage
problems);
• cleaning or removing mold-contaminated materials;
• removing materials with severe mold growth; and
• using high-efficiency air filters.
Moisture Control. Because one of the most important
factors affecting mold growth in homes is moisture level,
controlling this factor is crucial in mold abatement
strategies. Many simple measures can significantly control
moisture, for example maintaining indoor relative
humidity at no greater than 40%–60% through the use of
dehumidifiers, fixing water leakage problems, increasing
ventilation in kitchens and bathrooms by using exhaust
fans, venting clothes dryers to the outside, reducing the
number of indoor plants, using air conditioning at times
of high outdoor humidity, heating all rooms in the winter
and adding heating to outside wall closets, sloping
surrounding soil away from building foundations, fixing
gutters and downspouts, and using a sump pump in
basements prone to flooding [27]. Vapor barriers, sump
pumps, and aboveground vents can also be installed in
crawlspaces to prevent moisture problems [28].
Removal and Cleaning of Mold-contaminated
Materials. Nonporous (e.g., metals, glass, and hard plastics) and semiporous (e.g., wood and concrete) materials
contaminated with mold and that are still structurally
sound can often be cleaned with bleach-and-water solutions. However, in some cases, the material may not be easily cleaned or may be so severely contaminated that it may
have to be removed. It is recommended that porous materials (e.g., ceiling tiles, wallboards, and fabrics) that cannot
be cleaned be removed and discarded [29]. In severe cases,
clean-up and repair of mold-contaminated buildings may
be conducted using methods similar to those used for
abatement of other hazardous substances such as asbestos
[30]. For example, in situations of extensive colonization
(large surface areas greater than 100 square feet or where
the material is severely degraded), extreme precautions may
be required, including full containment (complete isolation
of work area) with critical barriers (airlock and decontamiHealthy Housing Reference Manual5-6 Chapter 5: Indoor Air Pollutants and Toxic Materials
nation room) and negative pressurization, personnel
trained to handle hazardous wastes, and the use of full-face
respirators with HEPA filters, eye protection, and disposable full-body covering [26].
Worker Protection When Conducting Mold
Assessment and Mitigation Projects. Activities such as
cleaning or removal of mold-contaminated materials in
homes, as well as investigations of mold contamination
extent, have the potential to disturb areas of mold growth
and release fungal spores and fragments into the air.
Recommended measures to protect workers during mold
remediation efforts depend on the severity and nature of
the mold contamination being addressed, but include the
use of well fitted particulate masks or respirators that
retain particles as small as 1 micrometer or less, disposable
gloves and coveralls, and protective eyewear [31].
Following are examples of guidance documents for
remediation of mold contamination:
• New York City Department of Health and Mental
Hygiene. Guidelines on Assessment and Remediation
of Fungi in Indoor Environments (available from
URL: http://www.nyc.gov/html/doh/html/epi/
moldrpt1.shtml).
• American Conference of Governmental Industrial
Hygienists (ACGIH) 1999 document, Biosaerosols:
Assessment and Control (can be ordered at URL
http://www.acgih.org/home.htm).
• American Industrial Hygiene Association (AIHA) 2004
document, Assessment, Remediation, and PostRemediation Verification of Mold in Buildings (can be
ordered at URL http://www.aiha.org)
• Environmental Protection Agency guidance, Mold
Remediation in Schools and Commercial Buildings
(includes many general principles also applicable to
residential mold mitigation efforts; available at URL:
http://www.epa.gov/iaq/molds/mold_remediation.
html)
• Environmental Protection Agency guidance, A Brief
Guide to Mold, Moisture, and Your Home (for
homeowners and renters on how to clean up residential
mold problems and how to prevent mold growth;
available at URL: http://www.epa.gov/iaq/molds/
images/moldguide.pdf)
• Canada Mortgage and Housing Corporation, Clean-up
Procedures for Mold in Houses, (provides qualitative
guidance for mold mitigation; can be ordered at URL:
https://www.cmhc-schl.gc.ca:50104/b2c/b2c/init.
do?language=en).
Figure 5.1 shows mold growth in the home.
Chemical Pollutants
Carbon Monoxide
Carbon monoxide (CO) is a significant combustion pollutant in the United States. CO is a leading cause of poisoning deaths [32]. According to the National Fire
Protection Association (NFPA), CO-related nonfire
deaths are often attributed to heating and cooking equipment. The leading specific types of equipment blamed for
CO-related deaths include gas-fueled space heaters, gasfueled furnaces, charcoal grills, gas-fueled ranges, portable
kerosene heaters, and wood stoves.
As with fire deaths, the risk for unintentional CO death is
highest for the very young (ages 4 years and younger) and
the very old (ages 75 years and older). CO is an odorless,
colorless gas that can cause sudden illness and death. It is a
result of the incomplete combustion of carbon. Headache,
dizziness, weakness, nausea, vomiting, chest pain, and confusion are the most frequent symptoms of CO poisoning.
According to the American Lung Association (ALA) [33],
breathing low levels of CO can cause fatigue and increase
chest pain in people with chronic heart disease. Higher
levels of CO can cause flulike symptoms in healthy people.
In addition, extremely high levels of CO cause loss of consciousness and death. In the home, any fuel-burning appliance that is not adequately vented and maintained can be
a potential source of CO. The following steps should be
followed to reduce CO (as well as sulfur dioxide and
oxides of nitrogen) levels:
• Never use gas-powered equipment, charcoal grills,
hibachis, lanterns, or portable camping stoves in
enclosed areas or indoors.
Figure 5.1. Mold Growth in the Home
5-7Chapter 5: Indoor Air Pollutants and Toxic MaterialsHealthy Housing Reference Manual
Ozone
Inhaling ozone can damage the
lungs. Inhaling small amounts of
ozone can result in chest pain,
coughing, shortness of breath, and
throat irritation. Ozone can also
exacerbate chronic respiratory diseases such as asthma. Susceptibility
to the effects of ozone varies from
person to person, but even healthy
people can experience respiratory
difficulties from exposure.
According to the North Carolina
Department of Health and
Human Services [34], the major
source of indoor ozone is outdoor
ozone. Indoor levels can vary from
10% of the outdoor air to levels as high as 80% of the
outdoor air. The Food and Drug Administration has set a
limit of 0.05 ppm of ozone in indoor air. In recent years,
there have been numerous advertisements for ion generators that destroy harmful indoor air pollutants. These
devices create ozone or elemental oxygen that reacts with
pollutants. EPA has reviewed the evidence on ozone generators and states: “available scientific evidence shows that
at concentrations that do not exceed public health standards, ozone has little potential to remove indoor air contaminants,” and “there is evidence to show that at
concentrations that do not exceed public health standards, ozone is not effective at removing many odor causing chemicals” [35].
Ozone is also created by the exposure of polluted air to
sunlight or ultraviolet light emitters. This ozone produced
outside of the home can infiltrate the house and react
with indoor surfaces, creating additional pollutants.
Environmental Tobacco Smoke or Secondhand Smoke
Like CO, environmental tobacco smoke (ETS; also
known as secondhand smoke), is a product of combustion. The National Cancer Institute (NCI) [36], states
that ETS is the combination of two forms of smoke from
burning tobacco products:
• Sidestream smoke, or smoke that is emitted between
the puffs of a burning cigarette, pipe, or cigar; and
• Mainstream smoke, or the smoke that is exhaled by
the smoker.
• Install a CO monitor (Figure 5.2) in appropriate areas
of the home. These monitors are designed to provide a
warning before potentially life-threatening levels of
CO are reached.
• Choose vented appliances when possible and keep gas
appliances properly adjusted to decrease the
combustion to CO. (Note: Vented appliances are
always preferable for several reasons: oxygen levels,
carbon dioxide buildup, and humidity management).
• Only buy certified and tested combustion appliances
that meet current safety standards, as certified by
Underwriter’s Laboratories (UL), American Gas
Association (AGA) Laboratories, or equivalent.
• Assure that all gas heaters possess safety devices that
shut off an improperly vented gas heater. Heaters
made after 1982 use a pilot light safety system known
as an oxygen depletion sensor. When inadequate fresh
air exists, this system shuts off the heater before large
amounts of CO can be produced.
• Use appliances that have electronic ignitions instead of
pilot lights. These appliances are typically more energy
efficient and eliminate the continuous low-level
pollutants from pilot lights.
• Use the proper fuel in kerosene appliances.
• Install and use an exhaust fan vented to the outdoors
over gas stoves.
• Have a trained professional annually inspect, clean,
and tune up central heating systems (furnaces, flues,
and chimneys) and repair them as needed.
• Do not idle a car inside a garage.
The U.S. Consumer Product Safety Commission (CPSC)
recommends installing at least one CO alarm per household near the sleeping area. For an extra measure of
safety, another alarm should be placed near the home’s
heating source. ALA recommends weighing the benefits
of using models powered by electrical outlets versus models powered by batteries that run out of power and need
replacing. Battery-powered CO detectors provide continuous protection and do not require recalibration in the
event of a power outage. Electric-powered systems do not
provide protection during a loss of power and can take
up to 2 days to recalibrate. A device that can be easily
self-tested and reset to ensure proper functioning should
be chosen. The product should meet Underwriters
Laboratories Standard UL 2034.
Figure 5.2. Home Carbon
Monoxide Monitor
Source: U.S. Navy
Healthy Housing Reference Manual5-8 Chapter 5: Indoor Air Pollutants and Toxic Materials
art supplies, cleaners, spot removers, floor waxes, polishes,
and air fresheners. The health effects of these chemicals
are varied. Trichlorethylene has been linked to childhood
leukemia. Exposure to toluene can put pregnant women
at risk for having babies with neurologic problems,
retarded growth, and developmental problems. Xylenes
have been linked to birth defects. Styrene is a suspected
endocrine disruptor, a chemical that can block or mimic
hormones in humans or animals. EPA data reveal that
methylene chloride, a common component of some paint
strippers, adhesive removers, and specialized aerosol spray
paints, causes cancer in animals [38]. Methylene chloride
is also converted to CO in the body and can cause symptoms associated with CO exposure. Benzene, a known
human carcinogen, is contained in tobacco smoke, stored
fuels, and paint supplies. Perchloroethylene, a product
uncommonly found in homes, but common to dry cleaners, can be a pollution source by off-gassing from newly
cleaned clothing. Environmental Media Services [39] also
notes that xylene, ketones, and aldehydes are used in
aerosol products and air fresheners.
To lower levels of VOCs in the home, follow these steps:
• use all household products according to directions;
• provide good ventilation when using these products;
• properly dispose of partially full containers of old or
unneeded chemicals;
• purchase limited quantities of products; and
• minimize exposure to emissions from products
containing methylene chloride, benzene, and
perchlorethylene.
A prominent VOC found in household products and
construction products is formaldehyde. According to
CPSC [40], these products include the glue or adhesive
used in pressed wood products; preservatives in paints,
coating, and cosmetics; coatings used for permanent-press
quality in fabrics and draperies; and the finish on paper
products and certain insulation materials. Formaldehyde
The physiologic effects of ETS are numerous. ETS can
trigger asthma; irritate the eyes, nose, and throat; and
cause ear infections in children, respiratory illnesses, and
lung cancer. ETS is believed to cause asthma by irritating
chronically inflamed bronchial passages. According to the
EPA [37], ETS is a Group A carcinogen; thus, it is a
known cause of cancer in humans. Laboratory analysis
has revealed that ETS contains in excess of 4,000 substances, more than 60 of which cause cancer in humans
or animals. The EPA also estimates that approximately
3,000 lung cancer deaths occur each year in nonsmokers
due to ETS. Additionally, passive smoking can lead to
coughing, excess phlegm, and chest discomfort. NCI also
notes that spontaneous abortion (miscarriage), cervical
cancer, sudden infant death syndrome, low birth weight,
nasal sinus cancer, decreased lung function, exacerbation
of cystic fibrosis, and negative cognitive and behavioral
effects in children have been linked to ETS [36].
The EPA [37] states that, because of their relative body
size and respiratory rates, children are affected by ETS
more than adults are. It is estimated that an additional
7,500 to 15,000 hospitalizations resulting from increased
respiratory infections occur in children younger than 18
months of age due to ETS exposure. Figure 5.3 shows the
ETS exposure levels in homes with children under age 7
years. The following actions are recommended in the
home to protect children from ETS:
• if individuals insist on smoking, increase ventilation in
the smoking area by opening windows or using
exhaust fans; and
• refrain from smoking in the presence of children and
do not allow babysitters or others who work in the
home to smoke in the home or near children.
Volatile Organic Compounds
In the modern home, many organic chemicals are used as
ingredients in household products. Organic chemicals
that vaporize and become gases at normal room
temperature are collectively known as VOCs.
Examples of common items that can release VOCs
include paints, varnishes, and wax, as well as in many
cleaning, disinfecting, cosmetic, degreasing, and hobby
products. Levels of approximately a dozen common
VOCs can be two to five times higher inside the home, as
opposed to outside, whether in highly industrialized areas
or rural areas. VOCs that frequently pollute indoor air
include toluene, styrene, xylenes, and trichloroethylene.
Some of these chemicals may be emitted from aerosol
products, dry-cleaned clothing, paints, varnishes, glues,
Figure 5.3. Environmental Tobacco Smoke and Children’s Exposure [37]
5-9Chapter 5: Indoor Air Pollutants and Toxic MaterialsHealthy Housing Reference Manual
is contained in urea-formaldehyde (UF) foam insulation
installed in the wall cavities of homes as an energy conservation measure. Levels of formaldehyde increase soon
after installation of this product, but these levels decline
with time. In 1982, CPSC voted to ban UF foam insulation. The courts overturned the ban; however, the publicity has decreased the use of this product.
More recently, the most significant source of formaldehyde in homes has been pressed wood products made
using adhesives that contain UF resins [41]. The most
significant of these is medium-density fiberboard, which
contains a higher resin-to-wood ratio than any other UF
pressed wood product. This product is generally recognized as being the highest formaldehyde-emitting pressed
wood product. Additional pressed wood products are produced using phenol-formaldehyde resin. The latter type
of resin generally emits formaldehyde at a considerably
slower rate than those containing UF resin. The emission
rate for both resins will change over time and will be
influenced by high indoor temperatures and humidity.
Since 1985, U.S. Department of Housing and Urban
Development (HUD) regulations (24 CFR 3280.308,
3280.309, and 3280.406) have permitted only the use of
plywood and particleboard that conform to specified
formaldehyde emission limits in the construction of prefabricated and manufactured homes [42]. This limit was
to ensure that indoor formaldehyde levels are below 0.4
ppm.
CPSC [40] notes that formaldehyde is a colorless, strongsmelling gas. At an air level above 0.1 ppm, it can cause
watery eyes; burning sensations in the eyes, nose, and
throat; nausea; coughing; chest tightness; wheezing; skin
rashes; and allergic reactions. Laboratory animal studies
have revealed that formaldehyde can cause cancer in animals and may cause cancer in humans. Formaldehyde is
usually present at levels less than 0.03 ppm indoors and
outdoors, with rural areas generally experiencing lower
concentrations than urban areas. Indoor areas that contain products that release formaldehyde can have levels
greater than 0.03 ppm. CPSC also recommends the following actions to avoid high levels of exposure to
formaldehyde:
• Purchase pressed wood products that are labeled or
stamped to be in conformance with American
National Standards Institute criteria ANSI A208.11993. Use particleboard flooring marked with ANSI
grades PBU, D2, or D3. Medium-density fiberboard
should be in conformance with ANSI A208.2-1994
and hardwood plywood with ANSI/HPVA HP-11994 (Figure 5.4).
• Purchase furniture or cabinets that contain a high
percentage of panel surface and edges that are
laminated or coated. Unlaminated or uncoated (raw)
panels of pressed wood panel products will generally
emit more formaldehyde than those that are laminated
or coated.
• Use alternative products, such as wood panel products
not made with UF glues, lumber, or metal.
• Avoid the use of foamed-in-place insulation containing
formaldehyde, especially UF foam insulation.
• Wash durable-press fabrics before use.
CPSC also recommends the following actions to reduce
existing levels of indoor formaldehyde:
• Ventilate the home well by opening doors and
windows and installing an exhaust fan(s).
• Seal the surfaces of formaldehyde-containing products
that are not laminated or coated with paint, varnish,
or a layer of vinyl or polyurethane-like materials.
• Remove products that release formaldehyde in the
indoor air from the home.
Radon
According to the EPA [43], radon is a colorless, odorless
gas that occurs naturally in soil and rock and is a decay
product of uranium. The U.S. Geological Survey (USGS)
[44] notes that the typical uranium content of rock and
the surrounding soil is between 1 and 3 ppm. Higher levels of uranium are often contained in rock such as lightcolored volcanic rock, granite, dark shale, and
sedimentary rock containing phosphate. Uranium levels
as high as 100 ppm may be present in various areas of the
United States because of these rocks. The main source of
high-level radon pollution in buildings is surrounding
uranium-containing soil. Thus, the greater the level of
uranium nearby, the greater the chances are that buildings
in the area will have high levels of indoor radon. Figure
5.5 demonstrates the geographic variation in radon levels
in the United States. Maps of the individual states and
areas that have proven high for radon are available at
Figure 5.4. Wood Products Label [42]
Healthy Housing Reference Manual5-10 Chapter 5: Indoor Air Pollutants and Toxic Materials
http://www.epa.gov/iaq/radon/ zonemap.html. A free
video is available from the U.S. EPA: call 1-800-4384318 and ask for EPA 402-V-02-003 (TRT 13.10).
Radon, according to the California Geological Survey
[45], is one of the intermediate radioactive elements
formed during the radioactive decay of uranium-238,
uranium-235, or thorium-232. Radon-222 is the radon
isotope of most concern to public health because of its
longer half-life (3.8 days). The mobility of radon gas is
much greater than are uranium and radium, which are
solids at room temperature. Thus, radon can leave rocks
and soil, move through fractures and pore spaces, and
ultimately enter a building to collect in high concentrations. When in water, radon moves less than 1 inch
before it decays, compared to 6 feet or more in dry rocks
or soil. USGS [44] notes that radon near the surface of
soil typically escapes into the atmosphere. However,
where a house is present, soil air often flows toward the
house foundation because of
• differences in air pressure between the soil and the
house, with soil pressure often being higher;
• presence of openings in the house’s foundation; and
• increases in permeability around the basement
(if present).
Figure 5.5. EPA Map of Radon Zones [43]
Zone 1: predicted average indoor radon screening level greater than
4 pCi/L [picocuries per liter]
Zone 2: predicted average indoor radon screening level between 2
and 4 pCi/L
Zone 3: predicted average indoor radon screening level less than 2
pCi/L
Important: Consult the EPA Map of Radon Zones document [EPA402-R-93-071] before using this map. This document contains information on radon potential variations within counties.
EPA also recommends that this map be supplemented with any available local data to further understand and predict the radon potential
of a specific area.
Houses are often constructed with loose fill under a basement slab and between the walls and exterior ground.
This fill is more permeable than the original ground.
Houses typically draw less than 1% of their indoor air
from the soil. However, houses with low indoor air pressures, poorly sealed foundations, and several entry points
for soil air may draw up to 20% of their indoor air from
the soil.
USGS [44] states that radon may also enter the home
through the water systems. Surface water sources typically
contain little radon because it escapes into the air. In
larger cities, radon is released to the air by municipal processing systems that aerate the water. However, in areas
where groundwater is the main water supply for communities, small public systems and private wells are typically
closed systems that do not allow radon to escape. Radon
then enters the indoor air from showers, clothes washing,
dishwashing, and other uses of water. Figure 5.6 shows
typical entry points of radon.
Health risks of radon stem from its breakdown into
“radon daughters,” which emit high-energy alpha particles. These progeny enter the lungs, attach themselves,
and may eventually lead to lung cancer. This exposure to
radon is believed to contribute to between 15,000 and
21,000 excess lung cancer deaths in the United States
each year. The EPA has identified levels greater than 4
picocuries per liter as levels at which remedial action
should be taken. Approximately 1 in 15 homes nationwide have radon above this level, according to the U.S.
Surgeon General’s recent advisory [46]. Smokers are at
significantly higher risk for radon-related lung cancer.
Figure 5.6. Radon Entry [30]
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Radon in the home can be measured either by the occupant or by a professional. Because radon has no odor or
color, special devices are used to measure its presence.
Radon levels vary from day to day and season to season.
Short-term tests (2 to 90 days) are best if quick results are
needed, but long-term tests (more than 3 months) yield
better information on average year-round exposure.
Measurement devices are routinely placed in the lowest
occupied level of the home. The devices either measure
the radon gas directly or the daughter products. The simplest devices are passive, require no electricity, and include
a charcoal canister, charcoal liquid scintillation device,
alpha tract detector, and electret ion detectors [47].
All of these devices, with the exception of the ion detector, can be purchased in hardware stores or by mail. The
ion detector generally is only available through laboratories. These devices are inexpensive, primarily used for
short-term testing, and require little to no training. Active
devices, however, need electrical power and include continuous monitoring devices. They are customarily more
expensive and require professionally trained testers for
their operation. Figure 5.7 shows examples of the charcoal
tester (a; left) and the alpha tract detector (b; right).
After testing and evaluation by a professional, it may be
necessary to lower the radon levels in the structure. The
Pennsylvania Department of Environmental Protection
[48] states that in most cases, a system with pipes and a
fan is used to reduce radon. This system, known as a subslab depressurization system, requires no major changes to
the home. The cost typically ranges from $500 to $2,500
and averages approximately $1,000, varying with geographic region. The typical mitigation system usually has
only one pipe penetrating through the basement floor; the
pipe also may be installed outside the house. The
Connecticut Department of Public Health [49] notes that
it is more cost effective to include radon-resistant techniques while constructing a building than to install a
Figure 5.7. Home Radon Detectors [31]
Figure 5.8. Radon-resistant Construction [50]
reduction system in an existing home. Inclusion of
radon-resistant techniques in initial construction costs
approximately $350 to $500 [50]. Figure 5.8 shows
examples of radon-resistant construction techniques.
A passive radon-resistant system has five major parts:
1. A layer of gas-permeable material under the foundation.
2. The foundation (usually 4 inches of gravel).
3. Plastic sheeting over the foundation, with all openings in
the concrete foundation floor sealed and caulked.
4. A gas-tight, 3- or 4-inch vent pipe running from under
the foundation through the house to the roof.
5. A roughed-in electrical junction box for the future
installation of a fan, if needed.
These features create a physical barrier to radon entry.
The vent pipe redirects the flow of air under the foundation, preventing radon from seeping into the house.
Pesticides
Much pesticide use could be reduced if integrated pest
management (IPM) practices were used in the home.
IPM is a coordinated approach to managing roaches,
rodents, mosquitoes, and other pests that integrates
inspection, monitoring, treatment, and evaluation, with
special emphasis on the decreased use of toxic agents.
However, all pest management options, including natural,
biologic, cultural, and chemical methods, should be considered. Those that have the least impact on health and
the environment should be selected. Most household
Healthy Housing Reference Manual5-12 Chapter 5: Indoor Air Pollutants and Toxic Materials
pests can be controlled by eliminating the habitat for the
pest both inside and outside, building or screening them
out, eliminating food and harborage areas, and safely
using appropriate pesticides if necessary.
EPA [51] states that 75% of U.S. households used at
least one pesticide indoors during the past year and that
80% of most people’s exposure to pesticides occurs
indoors. Measurable levels of up to a dozen pesticides
have been found in the air inside homes. Pesticides used
in and around the home include products to control
insects (insecticides), termites (termiticides), rodents
(rodenticides), fungi (fungicides), and microbes (disinfectants). These products are found in sprays, sticks, powders, crystals, balls, and foggers.
Delaplane [52] notes that the ancient Romans killed
insect pests by burning sulfur and controlled weeds with
salt. In the 1600s, ants were controlled with mixtures of
honey and arsenic. U.S. farmers in the late 19th century
used copper actoarsenite (Paris green), calcium arsenate,
nicotine sulfate, and sulfur to control insect pests in field
crops. By World War II and afterward, numerous pesticides had been introduced, including DDT, BHC,
aldrin, dieldrin, endrin, and 2,4-D. A significant factor
with regard to these pesticides used in and around the
home is their impact on children. According to a 2003
EPA survey, 47% of all households with children under
the age of 5 years had at least one pesticide stored in an
unlocked cabinet less than 4 feet off the ground. This is
within easy reach of children. Similarly, 74% of households without children under the age of 5 also stored
pesticides in an unlocked cabinet less than 4 feet off the
ground. This issue is significant because 13% of all pesticide poisoning incidents occur in homes other than the
child’s home. The EPA [53] notes a report by the
American Association of Poison Control Centers indicating that approximately 79,000 children were involved in
common household pesticide poisonings or exposures.
The health effects of pesticides vary with the product.
However, local effects from most of the products will be
on eyes, noses, and throats; more severe consequences,
such as on the central nervous system and kidneys and
on cancer risks, are possible. The active and inert ingredients of pesticides can be organic compounds, which can
contribute to the level of organic compounds in indoor
air. More significantly, products containing cyclodiene
pesticides have been commonly associated with misapplication. Individuals inadvertently exposed during this misapplication had numerous symptoms, including
headaches, dizziness, muscle twitching, weakness, tingling sensations, and nausea. In addition, there is concern that these pesticides may cause long-term damage to
the liver and the central nervous system, as well as an
increased cancer risk. Cyclodiene pesticides were developed for use as insecticides in the 1940s and 1950s. The
four main cyclodiene pesticides— aldrin, dieldrin, chlordane, and heptachlor— were used to guard soil and seed
against insect infestation and to control insect pests in
crops. Outside of agriculture they were used for ant control; farm, industrial, and domestic control of fleas, flies,
lice, and mites; locust control; termite control in buildings, fences, and power poles; and pest control in home
gardens. No other commercial use is permitted for cyclodiene or related products. The only exception is the use
of heptachlor by utility companies to control fire ants in
underground cable boxes.
An EPA survey [53] revealed that bathrooms and kitchens are areas in the home most likely to have improperly
stored pesticides. In the United States, EPA regulates pesticides under the pesticide law known as the Federal
Insecticide, Fungicide, and Rodenticide Act. Since 1981,
this law has required most residential-use pesticides to
bear a signal word such as “danger” or “warning” and to
be contained in child-resistant packaging. This type of
packaging is designed to prevent or delay access by most
children under the age of 5 years. EPA offers the following recommendations for preventing accidental
poisoning:
• store pesticides away from the reach of children in a
locked cabinet, garden shed, or similar location;
• read the product label and follow all directions exactly,
especially precautions and restrictions;
• remove children, pets, and toys from areas before
applying pesticides;
• if interrupted while applying a pesticide, properly
close the package and assure that the container is not
within reach of children;
• do not transfer pesticides to other containers that
children may associate with food or drink;
• do not place rodent or insect baits where small
children have access to them;
• use child-resistant packaging properly by closing the
container tightly after use;
• assure that other caregivers for children are aware of
the potential hazards of pesticides;
5-13Chapter 5: Indoor Air Pollutants and Toxic MaterialsHealthy Housing Reference Manual
• teach children that pesticides are poisons and should
not be handled; and
• keep the local Poison Control Center telephone
number available.
Toxic Materials
Asbestos
Asbestos, from the Greek word meaning “inextinguishable,” refers to a group of six naturally occurring mineral
fibers. Asbestos is a mineral fiber of which there are several types: amosite, crocidiolite, tremolite, actinolite,
anthrophyllite, and chrysotile. Chrysotile asbestos, also
known as white asbestos, is the predominant commercial
form of asbestos. Asbestos is strong, flexible, resistant to
heat and chemical corrosion, and insulates well. These
features led to the use of asbestos in up to 3,000 consumer products before government agencies began to
phase it out in the 1970s because of its health hazards.
Asbestos has been used in insulation, roofing, siding,
vinyl floor tiles, fireproofing materials, texturized paint
and soundproofing materials, heating appliances (such as
clothes dryers and ovens), fireproof gloves, and ironing
boards. Asbestos continues to be used in some products,
such as brake pads. Other mineral products, such as talc
and vermiculite, can be contaminated with asbestos.
The health effects of asbestos exposure are numerous and
varied. Industrial studies of workers exposed to asbestos
in factories and shipyards have revealed three primary
health risk concerns from breathing high levels of asbestos
fibers: lung cancer, mesothelioma (a cancer of the lining
of the chest and the abdominal cavity), and asbestosis (a
condition in which the lungs become scarred with fibrous
tissue).
The risk for all of these conditions is amplified as the
number of fibers inhaled increases. Smoking also
enhances the risk for lung cancer from inhaling asbestos
fibers by acting synergistically. The incubation period
(from time of exposure to appearance of symptoms) of
these diseases is usually about 20 to 30 years. Individuals
who develop asbestosis have typically been exposed to
high levels of asbestos for a long time. Exposure levels to
asbestos are measured in fibers per cubic centimeter of
air. Most individuals are exposed to small amounts of
asbestos in daily living activities; however, a preponderance of them do not develop health problems. According
to the Agency for Toxic Substances and Disease Registry
(ATSDR), if an individual is exposed, several factors
determine whether the individual will be harmed [54].
These factors include the dose (how much), the duration
(how long), and the fiber type (mineral form and distribution). ATSDR also states that children may be more
adversely affected than adults [54]. Children breathe differently and have different lung structures than adults;
however, it has not been determined whether these differences cause a greater amount of asbestos fibers to stay in
the lungs of a child than in the lungs of an adult. In addition, children drink more fluids per kilogram of body
weight than do adults and they can be exposed through
asbestos-contaminated drinking water. Eating asbestoscontaminated soil and dust is another source of exposure
for children. Certain children intentionally eat soil and
children’s hand-to-mouth activities mean that all young
children eat more soil than do adults. Family members
also have been exposed to asbestos that was carried home
on the clothing of other family members who worked in
asbestos mines or mills. Breathing asbestos fibers may
result in difficulty in breathing. Diseases usually appear
many years after the first exposure to asbestos and are
therefore not likely to be seen in children. But people who
have been exposed to asbestos at a young age may be
more likely to contract diseases than those who are first
exposed later in life. In the small number of studies that
have specifically looked at asbestos exposure in children,
there is no indication that younger people might develop
asbestos-related diseases more quickly than older people.
Developing fetuses and infants are not likely to be
exposed to asbestos through the placenta or breast milk of
the mother. Results of animal studies do not indicate that
exposure to asbestos is likely to result in birth defects.
A joint document issued by CPSC, EPA, and ALA, notes
that most products in today’s homes do not contain asbestos. However, asbestos can still be found in products and
areas of the home. These products contain asbestos that
could be inhaled and are required to be labeled as such.
Until the 1970s, many types of building products and
insulation materials used in homes routinely contained
asbestos. A potential asbestos problem both inside and
outside the home is that of vermiculite. According to the
USGS [55], vermiculite is a claylike material that expands
when heated to form wormlike particles. It is used in concrete aggregate, fertilizer carriers, insulation, potting soil,
and soil conditioners. This product ceased being mined in
1992, but old stocks may still be available. Common
products that contained asbestos in the past and conditions that may release fibers include the following:
• Steam pipes, boilers, and furnace ducts insulated with
an asbestos blanket or asbestos paper tape. These
materials may release asbestos fibers if damaged,
repaired, or removed improperly.
Healthy Housing Reference Manual5-14 Chapter 5: Indoor Air Pollutants and Toxic Materials
• Resilient floor tiles (vinyl asbestos, asphalt, and
rubber), the backing on vinyl sheet flooring, and
adhesives used for installing floor tile. Sanding tiles can
release fibers, as may scraping or sanding the backing
of sheet flooring during removal.
• Cement sheet, millboard, and paper used as insulation
around furnaces and wood-burning stoves. Repairing
or removing appliances may release asbestos fibers, as
may cutting, tearing, sanding, drilling, or sawing
insulation.
• Door gaskets in furnaces, wood stoves, and coal stoves.
Worn seals can release asbestos fibers during use.
• Soundproofing or decorative material sprayed on walls
and ceilings. Loose, crumbly, or water-damaged
material may release fibers, as will sanding, drilling, or
scraping the material.
• Patching and joint compounds for walls, ceilings, and
textured paints. Sanding, scraping, or drilling these
surfaces may release asbestos.
• Asbestos cement roofing, shingles, and siding. These
products are not likely to release asbestos fibers unless
sawed, drilled, or cut.
• Artificial ashes and embers sold for use in gas-fired
fireplaces in addition to other older household
products such as fireproof gloves, stove-top pads,
ironing board covers, and certain hair dryers.
• Automobile brake pads and linings, clutch facings, and
gaskets.
Homeowners who believe material in their home may be
asbestos should not disturb the material. Generally, material in good condition will not release asbestos fibers, and
there is little danger unless the fibers are released and
inhaled into the lungs. However, if disturbed, asbestos
material may release asbestos fibers, which can be inhaled
into the lungs. The fibers can remain in the lungs for a
long time, increasing the risk for disease. Suspected asbestos-containing material should be checked regularly for
damage from abrasions, tears, or water. If possible, access
to the area should be limited. Asbestos-containing products
such as asbestos gloves, stove-top pads, and ironing board
covers should be discarded if damaged or worn. Permission
and proper disposal methods should be obtainable from
local health, environmental, or other appropriate officials.
If asbestos material is more than slightly damaged, or if
planned changes in the home might disturb it, repair or
removal by a professional is needed. Before remodeling,
determine whether asbestos materials are present.
Only a trained professional can confirm suspected asbestos materials that are part of a home’s construction. This
individual will take samples for analysis and submit them
to an EPA-approved laboratory.
If the asbestos material is in good shape and will not be
disturbed, the best approach is to take no action and continue to monitor the material. If the material needs action
to address potential exposure problems, there are two
approaches to correcting the problem: repair and removal.
Repair involves sealing or covering the asbestos material.
Sealing or encapsulation involves treating the material
with a sealant that either binds the asbestos fibers
together or coats the material so fibers are not released.
This is an approach often used for pipe, furnace, and
boiler insulation; however, this work should be done only
by a professional who is trained to handle asbestos safely.
Covering (enclosing) involves placing something over or
around the material that contains asbestos to prevent
release of fibers. Exposed insulated piping may be covered
with a protective wrap or jacket. In the repair process, the
approach is for the material to remain in position undisturbed. Repair is a less expensive process than is removal.
With any type of repair, the asbestos remains in place.
Repair may make later removal of asbestos, if necessary,
more difficult and costly. Repairs can be major or minor.
Both major and minor repairs must be done only by a
professional trained in methods for safely handling
asbestos.
Removal is usually the most expensive and, unless
required by state or local regulations, should be the last
option considered in most situations. This is because
removal poses the greatest risk for fiber release. However,
removal may be required when remodeling or making
major changes to the home that will disturb asbestos
material. In addition, removal may be called for if asbestos material is damaged extensively and cannot be otherwise repaired. Removal is complex and must be done only
by a contractor with special training. Improper removal
of asbestos material may create more of a problem than
simply leaving it alone.
Lead
Many individuals recognize lead in the form often seen in
tire weights and fishing equipment, but few recognize its
various forms in and around the home. The MerriamWebster Dictionary [56] defines lead as “a heavy soft malleable ductile plastic but inelastic bluish white metallic
element found mostly in combination and used especially
in pipes, cable sheaths, batteries, solder, and shields
5-15Chapter 5: Indoor Air Pollutants and Toxic MaterialsHealthy Housing Reference Manual
against radioactivity.” Lead is a metal with many uses. It
melts easily and quickly. It can be molded or shaped into
thin sheets and can be drawn out into wire or threads.
Lead also is very resistant to weather conditions. Lead
and lead compounds are toxic and can present a severe
hazard to those who are overexposed to them. Whether
ingested or inhaled, lead is readily absorbed and distributed throughout the body.
Until 1978, lead compounds were an important component of many paints. Lead was added to paint to promote adhesion, corrosion control, drying, and covering.
White lead (lead carbonate), linseed oil, and inorganic
pigments were the basic components for paint in the
18th and 19th centuries, and continued until the middle
of the 20th century. Lead was banned by CPSC in 1978.
Lead-based paint was used extensively on exteriors and
interior trim-work, window sills, sashes, window frames,
baseboards, wainscoting, doors, frames, and high-gloss
wall surfaces, such as those found in kitchens and bathrooms. The only way to determine which building components are coated with lead paint is through an
inspection for lead-based paint. Almost all painted metals were primed with red lead or painted with lead-based
paints. Even milk (casein) and water-based paints (distemper and calcimines) could contain some lead, usually
in the form of hiding agents or pigments. Varnishes
sometimes contained lead. Lead compounds also were
used as driers in paint and window-glazing putty.
Lead is widespread in the environment. People absorb
lead from a variety of sources every day. Although lead
has been used in numerous consumer products, the most
important sources of lead exposure to children and others today are the following:
• contaminated house dust that has settled on
horizontal surfaces,
• deteriorated lead-based paint,
• contaminated bare soil,
• food (which can be contaminated by lead in the air or
in food containers, particularly lead-soldered food
containers),
• drinking water (from corrosion of plumbing systems),
and
• occupational exposure or hobbies.
Federal controls on lead in gasoline, new paint, food
canning, and drinking water, as well as lead from industrial air emissions, have significantly reduced total
human exposure to lead. The number of children with
blood lead levels above 10 micrograms per deciliter (µg/
dL), a level designated as showing no physiologic toxicity,
has declined from 1.7 million in the late 1980s to
310,000 in 1999–2002. This demonstrates that the controls have been effective, but that many children are still
at risk. CDC data show that deteriorated lead-based paint
and the contaminated dust and soil it generates are the
most common sources of exposure to children today.
HUD data show that the number of houses with lead
paint declined from 64 million in 1990 to 38 million in
2000 [57].
Children are more vulnerable to lead poisoning than are
adults. Infants can be exposed to lead in the womb if
their mothers have lead in their bodies. Infants and children can swallow and breathe lead in dirt, dust, or sand
through normal hand-to-mouth contact while they play
on the floor or ground. These activities make it easier for
children to be exposed to lead. Other sources of exposure
have included imported vinyl miniblinds, crayons, children’s jewelry, and candy. In 2004, increases in lead in
water service pipes were observed in Washington, D.C.,
accompanied by increases in blood lead levels in children
under the age of 6 years who were served by the water
system [58].
In some cases, children swallow nonfood items such as
paint chips. These may contain very large amounts of
lead, particularly in and around older houses that were
painted with lead-based paint. Many studies have verified
the effect of lead exposure on IQ scores in the United
States. The effects of lead exposure have been reviewed by
the National Academy of Sciences [59].
Generally, the tests for blood lead levels are from drawn
blood, not from a finger-stick test, which can be unreliable if performed improperly. Units are measured in
micrograms per deciliter and reflect the 1991 guidance
from the Centers of Disease Control [60]:
• Children: 10 µg/dL (level of concern)— find source of
lead;
• Children: 15 µg/dL and above— environmental
intervention, counseling, medical monitoring;
• Children: 20 µg/dL and above— medical treatment;
• Adults: 25 µg/dL (level of concern)— find source of
lead; and
• Adults: 50 µg/dL— Occupational Safety and Health
Administration (OSHA) standard for medical removal
from the worksite.
Healthy Housing Reference Manual5-16 Chapter 5: Indoor Air Pollutants and Toxic Materials
Adults are usually exposed to lead from occupational
sources (e.g., battery construction, paint removal) or at
home (e.g., paint removal, home renovations).
In 1978, CPSC banned the use of lead-based paint in
residential housing. Because houses are periodically
repainted, the most recent layer of paint will most likely
not contain lead, but the older layers underneath probably will. Therefore, the only way to accurately determine
the amount of lead present in older paint is to have it
analyzed.
It is important that owners of homes built before 1978
be aware that layers of older paint can contain a great
deal of lead. Guidelines on identifying and controlling
lead-based paint hazards in housing have been published
by HUD [61].
Controlling Lead Hazards
The purpose of a home risk assessment is to determine,
through testing and evaluation, where hazards from lead
warrant remedial action. A certified inspector or risk
assessor can test paint, soil, or lead dust either on-site or
in a laboratory using methods such as x-ray fluorescence
(XRF) analyzers, chemicals, dust wipe tests, and atomic
absorption spectroscopy. Lists of service providers are
available by calling 1-800-424-LEAD. Do-it-yourself test
kits are commercially available; however, these kits do
not tell you how much lead is present, and their reliability at detecting low levels of lead has not been determined. Professional testing for lead in paint is
recommended. The recommended sampling method for
dust is the surface wet wipe. Dust samples are collected
from different surfaces, such as bare floors, window sills,
and window wells. Each sample is collected from a measured surface area using a wet wipe, which is sent to a
Lead in paint. Differing methods report results in differing
units. Lead is considered a potential hazard if above the following levels, but can be a hazard at lower levels if improperly handled. Below are the current action levels identified by
HUD [62] and EPA (40 CFR Part 745):
Lab analysis of samples:
5,000 milligram per kilogram (mg/kg) or 5,000 parts per
million (ppm) 0.5% lead by weight.
X-ray fluorescence:
1 milligram per square centimeter (mg/cm2)
Lead in dust:
Floors, 40 micrograms per square foot (µg/ft2)
Window sills, 250 µg/ft2 Window troughs, 400 µg/ft2
(clearance only)
Lead in soil:
High-contact bare play areas: 400 ppm
Other yard areas: 1,200 ppm
Action Levels for Lead
laboratory for testing. Risk assessments can be fairly lowcost investigations of the location, condition, and severity
of lead hazards found in house dust, soil, water, and deteriorating paint. Risk assessments also will address other
sources of lead from hobbies, crockery, water, and work
environments. These services are critical when owners are
seeking to implement measures to reduce suspected lead
hazards in housing and day-care centers or when extensive rehabilitation is planned.
HUD has published detailed protocols for risk assessments and inspections [61].
It is important from a health standpoint that future tenants, painters, and construction workers know that leadbased paint is present, even under treated surfaces, so
they can take precautions when working in areas that will
generate lead dust. Whenever mitigation work is completed, it is important to have a clearance test using the
dust wipe method to ensure that lead-laden dust generated during the work does not remain at levels above
those established by the EPA and HUD. Such testing is
required for owners of most housing that is receiving federal financial assistance, such as Section 8 rental housing.
A building or housing file should be maintained and
updated whenever any additional lead hazard control
work is completed. Owners are required by law to disclose information about lead-based paint or lead-based
paint hazards to buyers or tenants before completing a
sales or lease contract [62].
All hazards should be controlled as identified in a risk
assessment.
Whenever extensive amounts of lead must be removed
5-17Chapter 5: Indoor Air Pollutants and Toxic MaterialsHealthy Housing Reference Manual
from a property, or when methods of removing toxic
substances will affect the environment, it is extremely
important that the owner be aware of the issues surrounding worker safety, environmental controls, and
proper disposal. Appropriate architectural, engineering,
and environmental professionals should be consulted
when lead hazard projects are complex.
Following are brief explanations of the two approaches
for controlling lead hazard risks. These controls are recommended by HUD in HUD Guidelines for the
Evaluation and Control of Lead-Based Paint Hazards in
Housing [61], and are summarized here to focus on special considerations for historic housing:
Interim Controls. Short-term solutions include thorough dust removal and thorough washdown and
cleanup, paint film stabilization and repainting, covering
of lead-contaminated soil, and informing tenants about
lead hazards. Interim controls require ongoing maintenance and evaluation.
Hazard Abatement. Long-term solutions are defined as
having an expected life of 20 years or more and involve
permanent removal of hazardous paint through chemicals, heat guns, or controlled sanding or abrasive methods; permanent removal of deteriorated painted features
through replacement; removal or permanent covering of
contaminated soil; and the use of enclosures (such as
drywall) to isolate painted surfaces. The use of specialized encapsulant products can be considered as permanent abatement of lead.
Deteriorated lead-based paint: Paint known to contain lead above the regulated level that shows signs of peeling, chipping,
chalking, blistering, alligatoring, or otherwise separating from its substrate.
Dust removal: The process of removing dust to avoid creating a greater problem of spreading lead particles; usually through
wet or damp collection and use of HEPA vacuums.
Hazard abatement: Long-term measures to remove the hazards of lead-based paint through replacement of building components, enclosure, encapsulation, or paint removal.
Interim control: Short-term methods to remove lead dust, stabilize deteriorating painted surfaces, treat friction and impact
surfaces that generate lead dust, and repaint surfaces. Maintenance can ensure that housing remains lead-safe.
Lead-based paint: Any existing paint, varnish, shellac, or other coating that is equal to or greater than 1.0 milligrams per
square centimeter (mg/cm2) or greater than 0.5% by weight (5,000 ppm, 5,000 micrograms per gram [µg/g], or 5,000 milligrams per kilogram [mg/kg]). For new paint, CPSC has established 0.06% as the maximum amount of lead allowed in new
paint. Lead in paint can be measured by x-ray fluorescence analyzers or laboratory analysis by certified personnel and approved laboratories.
Risk assessment: An on-site investigation to determine the presence and condition of lead-based paint, including limited test
samples and an evaluation of the age, condition, housekeeping practices, and uses of a residence.
Definitions Related to Lead
Reducing and controlling lead hazards can be successfully
accomplished without destroying the character-defining
features and finishes of historic buildings. Federal and
state laws generally support the reasonable control of
lead-based paint hazards through a variety of treatments,
ranging from modified maintenance to selective substrate
removal. The key to protecting children, workers, and the
environment is to be informed about the hazards of lead,
to control exposure to lead dust and lead in soil and lead
paint chips, and to follow existing regulations.
The following summarizes several important regulations
that affect lead-hazard reduction projects. Owners should
be aware that regulations change, and they have a responsibility to check state and local ordinances as well. Care
must be taken to ensure that any procedures used to
release lead from the home protect both the residents and
workers from lead dust exposure.
Residential Lead-Based Paint Hazard Reduction Act of
1992, Title X [62]. Part of the Housing and Community
Development Act of 1992 (Public Law 102-550) [63]. It
established that HUD issue Guidelines for the Evaluation
and Control of Lead-Based Paint Hazards in Housing [61]
to outline risk assessments, interim controls, and abatement of lead-based paint hazards in housing. Title X calls
for the reduction of lead in federally supported housing.
It outlines the federal responsibility toward its own residential units and the need for disclosure of lead in residences, even private residences, before a sale. Title X also
required HUD to establish regulations for federally
assisted housing (24 CFR Part 35) and EPA to establish
Healthy Housing Reference Manual5-18 Chapter 5: Indoor Air Pollutants and Toxic Materials
standards for lead in paint, dust, and soil, as well as standards for laboratory accreditation (40 CFR Part 745).
EPA’s residential lead hazard standards are available at
http://www.epa.gov/lead/leadhaz.htm.
Interim Final Rule on Lead in Construction (29 Code
of Federal Regulations [CFR] 1926.62) [64]. Issued by
OSHA, these regulations address worker safety, training,
and protective measures. The regulations are based in part
on personal-air sampling to determine the amount of lead
dust exposure to workers.
State Laws. States generally have the authority to regulate
the removal and transportation of lead-based paint and
the generated waste through the appropriate state environmental and public health agencies. Most requirements
are for mitigation in the case of a lead-poisoned child, for
protection of children, or for oversight to ensure the safe
handling and disposal of lead waste. When undertaking a
lead-based paint reduction program, it is important to
determine which laws are in place that may affect the
project.
Local Ordinances. Check with local health departments,
poison control centers, and offices of housing and community development to determine whether any laws
require compliance by building owners. Determine
whether projects are considered abatements and will
require special contractors and permits.
Owner’s Responsibility. Owners are ultimately responsible for ensuring that hazardous waste is properly disposed
of when it is generated on their own sites. Owners should
check with their state government to determine whether
an abatement project requires a certified contractor.
Owners should establish that the contractor is responsible
for the safety of the crew, to ensure that all applicable
laws are followed, and that transporters and disposers of
hazardous waste have liability insurance as a protection
for the owner. The owner should notify the contractor
that lead-based paint may be present and that it is the
contractor’s responsibility to follow appropriate work
practices to protect workers and to complete a thorough
cleanup to ensure that lead-laden dust is not present after
the work is completed. Renovation contractors are
required by EPA to distribute an informative educational
pamphlet (Protect Your Family from Lead in Your Home)
to occupants before starting work that could disturb leadbased paint (http://www.epa.gov/lead/ leadinfo.
htm#remodeling).
Arsenic
Lead arsenate was used legally up to 1988 in most of the
orchards in the United States. Often 50 applications or
more of this pesticide were applied each year. This toxic
heavy metal compound has accumulated in the soil
around houses and under the numerous orchards in the
country, contaminating both wells and land. These
orchards are often turned into subdivisions as cities
expand and sprawl occurs. Residues from the pesticide
lead arsenate, once used heavily on apple, pear, and other
orchards, contaminate an estimated 70,000 to 120,000
acres in the state of Washington alone, some of it in areas
where agriculture has been replaced with housing, according to state ecology department officials and others.
Lead arsenate, which was not banned for use on food
crops until 1988, nevertheless was mostly replaced by the
pesticide dichlorodiphenyltrichloroethane (DDT) and its
derivatives in the late 1940s. DDT was banned in the
United States in 1972, but is used elsewhere in the world.
For more than 20 years, the wood industry has infused
green wood with heavy doses of arsenic to kill bugs and
prevent rot. Numerous studies show that arsenic sticks to
children’s hands when they play on treated wood, and it
is absorbed through the skin and ingested when they put
their hands in their mouths. Although most uses of arsenic wood treatments were phased out by 2004, an estimated 90% of existing outdoor structures are made of
arsenic-treated wood [65].
In a study conducted by the University of North Carolina
Environmental Quality Institute in Asheville, wood samples were analyzed and showed that
• Older decks and play sets (7 to 15 years old) that were
preserved with chromated copper arsenic expose
people to just as much arsenic on the wood surface as
do newer structures (less than 1 year old). The amount
of arsenic that testers wiped off a small area of wood
about the size of a 4-year-old’s handprint typically far
exceeds what EPA allows in a glass of water under the
Safe Drinking Water Act standard. Figure 5.9 shows a
safety warning label placed on wood products.
• Arsenic in the soil from two of every five backyards or
parks tested exceeded EPA’s Superfund cleanup level of
20 ppm.
Arsenic is not just poisonous in the short term, it causes
cancer in the long term. Arsenic is on EPA’s short list of
chemicals known to cause cancer in humans. According
to the National Academy of Sciences, exposure to arsenic
5-19Chapter 5: Indoor Air Pollutants and Toxic MaterialsHealthy Housing Reference Manual
6. Community Environmental Health Resource Center.
Cockroaches: tools for detecting hazards. Washington,
DC: Community Environmental Health Resource
Center; no date. Available from URL: http://www.cehrc.
org/tools/cockroaches/index.cfm.
7. Lyon WF. Entomology, House Dust Mites HYG
2157-97. Columbus, OH: The Ohio State University
Extension; 1997. Available from URL: http://ohioline.osu.
edu/hyg-fact/2000/2157.html.
8. Morgan WJ, Crain EF, Gruchalla RS, O’Connor GT,
Kattan M, et al. Results of a home-based environmental
intervention among urban children with asthma. N Engl J
Med 2004;351:1068–80.
9. US Environmental Protection Agency. Sources of indoor
air pollution— biological pollutants. Washington, DC: US
Environmental Protection Agency; no date. Available from
URL: http://www.epa.gov/iaq/biologic.html.
10. Ownby DR. Exposure to dogs and cats in the first year of
life and risk of allergic sensitization at 6 to 7 years of age.
JAMA 2002;288(8):963–72.
11. Roost HP. Role of current and childhood exposure to cat
and atopic sensitization. J Allergy Clin Immunol
1999;104(5):94.
12. Downs SH. Having lived on a farm and protection
against allergic diseases in Australia. Clin Exp Allergy
2001;31(4):570–5.
13. Institute of Medicine. Clearing the air: asthma and indoor
air exposures. Washington, DC: National Academies Press;
2000.
14. American Conference of Governmental and Industrial
Hygienists. Macher J, editor. Bioaerosols: assessment and
control. Cincinnati, OH: American Conference of
Governmental and Industrial Hygienists; 1999.
15. Institute of Medicine. Damp indoor spaces and health.
Washington, DC: National Academies Press; 2004.
16. Morgan WJ, Crain EF, Gruchalla RS, O’Connor GT,
Kattan M, Evans R 3rd, et al. Results of home-based
environmental intervention among urban children with
asthma. N Engl J Med 2004;351:1068–80.
17. Burge HA, Ammann HA. Fungal toxins and ß (1→3)d-glucans. In: Macher J, editor. Bioaerosols: assessment
and control. Cincinnati, OH: American Conference of
Governmental and Industrial Hygienists; 1999.
18. American Academy of Pediatrics, Committee on
Environmental Health. Toxic effects of indoor molds.
Pediatrics 1998;101:712–14.
causes lung, bladder, and skin cancer in humans, and is
suspected as a cause of kidney, prostate, and nasal passage
cancer.
References
1. US Environmental Protection Agency and the US
Consumer Product Safety Commission. The inside
story: a guide to indoor air quality. Washington, DC:
US Environmental Protection Agency and the US
Consumer Product Safety Commission, Office of
Radiation and Indoor Air; 1995. Document
#402-K-93-007. Available from URL: http://www.
epa.gov/iaq/pubs/insidest.html.
2. Centers for Disease Control and Prevention. Asthma:
speaker’s kit for health care professionals; preface. Atlanta:
US Department of Health and Human Services; no date.
Available from URL: http://www.cdc.gov/asthma/speakit/
intro.htm.
3. US Environmental Protection Agency. Washington, DC:
US Environmental Protection Agency; 2004. Asthma
facts. EPA #402-F-04-019. Available from URL: http://
www.epa.gov/asthma/pdfs/asthma_fact_sheet_en.pdf.
4. Centers for Disease Control and Prevention. Asthma:
speaker’s kit for health care professionals; epidemiology.
Atlanta: US Department of Health and Human Services;
no date. Available from URL: http://www.cdc.gov/
asthma/speakit/epi.htm.
5. Crain EF, Walter M, O’Connor GT, Mitchell H,
Gruchalla RS, Kattan M, et al. Home and allergic
characteristics of children with asthma in seven U.S. urban
communities and design of an environmental
intervention: The Inner-City Asthma Study. Environ
Health Perspect 2002;119:939–45.
Figure 5.9. Arsenic Label
Healthy Housing Reference Manual5-20 Chapter 5: Indoor Air Pollutants and Toxic Materials
29. US Environmental Protection Agency. Mold remediation
in schools and commercial buildings (EPA
402-K-01-001). Washington, DC: US Environmental
Protection Agency; 2001.
30. Shaughnessy RJ, Morey PR. Remediation of microbial
contamination. In: Macher J, editor. Bioaerosols:
assessment and control. Cincinnati, OH: American
Conference of Governmental and Industrial Hygienists;
1999.
31. National Institute of Environmental Health Sciences.
Interim final guidelines for the protection and training of
workers engaged in maintenance and remediation work
associated with mold. Report of a national technical
workshop, National Institute of Environmental Health
Sciences, New York City, 2004 Jan 27–28.
32. Mott JA, Wolfe MI, Alverson CJ, Macdonald SC, Bailey
CR, Ball LB, et al. National vehicle emissions policies and
practices and declining US carbon monoxide mortality.
JAMA 2002;288:988–95.
33. American Lung Association. Carbon monoxide fact sheet.
New York: American Lung Association; 2004. Available
from URL: http://www.lungusa.org/site/pp.
asp?c=dvLUK9O0E&b=35375.
34. North Carolina Department of Health and Human
Services. Indoor ozone. Raleigh, NC: North Carolina
Department of Health and Human Services; 2003.
Available from URL: http://www.epi.state.nc.us/epi/oee/
ozone/indoor.html.
35. US Environmental Protection Agency. Ozone generators
that are sold as air cleaners: an assessment of effectiveness
and health consequences. Washington, DC: US
Environmental Protection Agency; no date. Available from
URL: http://www.epa.gov/iaq/pubs/ozonegen.html.
36. National Cancer Institute. Secondhand smoke: questions
and answers. Bethesda, MD: National Cancer Institute;
no date. Available from URL: http://www.cancer.gov/
cancertopics/factsheet/Tobacco/ETS.
37. US Environmental Protection Agency. What you can do
about secondhand smoke as parents, decision-makers, and
building occupants. Washington, DC: US Environmental
Protection Agency; 1993. Available from URL: http://
www.epa.gov/smokefree/pubs/etsbro.html.
38. US Environmental Protection Agency. Methylene chloride
(dichloromethane). Washington, DC: US Environmental
Protection Agency; 1992. Available from URL: http://
www.epa.gov/ttnatw01/hlthef/methylen.html.
19. Burge HA, Otten JA. 1999. Fungi. In: Macher J, editor.
Bioaerosols: assessment and control. Cincinnati, OH:
American Conference of Governmental and Industrial
Hygienists; 1999.
20. Etzel RA. The “fatal four” indoor air pollutants. Pediatr
Ann 2000;29(6):344–50.
21. Dearborn DG, Smith PG, Dahms BB, Allan TM,
Sorenson WG, Montana E, et al. Clinical profile of thirty
infants with acute pulmonary hemorrhage in Cleveland.
Pediatrics 2002;110:627–37.
22. Etzel RA, Montana E, Sorenson WG, Kullman GJ, Allan
TM, Dearborn DG. Acute pulmonary hemorrhage in
infants associated with exposure to Stachybotrys atra and
other fungi. Arch Pediatr Adolesc Med 1998;152:757–62.
23. Flappan SM, Portnoy J, Jones P, Barnes C. Infant
pulmonary hemorrhage in a suburban home with water
damage and mold (Stachybotrys atra). Environ Health
Perspect 1999;107:927–30.
24. Vesper S, Dearborn DG, Yike I, Allan T, Sobolewski J,
Hinkley SF, et al. Evaluation of Stachybotrys chartarum in
the house of an infant with pulmonary hemorrhage:
quantitative assessment before, during, and after
remediation. J. Urban Health Bull N Y Acad Med
2000;77(1):68–85.
25. US Environmental Protection Agency. A brief guide to
mold, moisture, and your home (EPA 402-K-02-003).
Washington, DC: US Environmental Protection Agency;
2002. Available from URL: http://www.epa.gov/iaq/
molds/images/moldguide.pdf.
26. NYC. 2000. Guidelines on assessment and remediation of
fungi in indoor environments. New York City
Department of Health, Bureau of Environmental &
Occupational Disease Epidemiology. Available from URL:
http://www.ci.nyc.ny.us/html/doh/html/epi/moldrpt1.
shtml.
27. Bush RK, Portnoy JM. The role and abatement of fungal
allergens in allergic diseases. J Allerg Clin Immunol Suppl
2001;107(3 pt 2):430.
28. Department of Housing and Urban Development, Office
of Native American Programs. Mold detection and
prevention: a guide for housing authorities in Indian
Country. Washington, DC: Department of Housing and
Urban Development; 2001. Available from URL: http://
www2.ihs.gov/IEH/documents/HUD%20Mold%20
Detection.pdf.
5-21Chapter 5: Indoor Air Pollutants and Toxic MaterialsHealthy Housing Reference Manual
39. Environmental Media Services. Four to avoid.
Washington, DC: Environmental Media Services; 2002.
40. US Consumer Product Safety Commission. An update on
formaldehyde: 1997 revision. Washington, DC:
Consumer Product Safety Commission; 1997. CPSC
Document 725. Available from URL: http://www.cpsc.
gov/cpscpub/pubs/725.html.
41. US Environmental Protection Agency. Sources of indoor
air pollution— formaldehyde. Washington, DC: US
Environmental Protection Agency. Available from URL:
http://www.epa.gov/iaq/formalde.html.
42. US Department of Housing and Urban Development.
Formaldehyde emission controls for certain wood
products. 24 CFR3280.308. Washington, DC: US
Department of Housing and Urban Development;
2001. Available from URL: http://www.hudclips.org/cgi/
index.cgi.
43. US Environmental Protection Agency. Assessment of risks
from radon in homes. Washington, DC: US
Environmental Protection Agency; 2003. Available from
URL: http://www.epa.gov/radon/risk_assessment.html.
44. US Geological Survey. The geology of radon. Reston, VA:
US Geological Survey; 1995. Available from URL: http://
energy.cr.usgs.gov/radon/georadon/3.html.
45. California Geological Survey. Radon. Sacramento, CA:
California Geological Survey; no date. Available from
URL: http://www.consrv.ca.gov/ cgs/minerals/hazardous_
minerals/radon/.
46. US Department of Health and Human Services. Surgeon
General releases national health advisory on radon.
Washington, DC: US Department of Health and Human
Services; 2005. Available from URL: http://www.hhs.gov/
surgeongeneral/pressreleases/sg01132005.html.
47. Brain M, Freudenrich C. How radon works. Atlanta:
How Stuff Works; no date. Available from URL: http://
home.howstuffworks.com/radon.htm.
48. Pennsylvania Department of Environmental Protection.
Mitigating your home or office. Harrisburg, PA:
Pennsylvania Department of Environmental Protection;
no date. Available from URL: http://www.dep.state.pa.us/
dep/deputate/airwaste/rp/radon_division/Mitigation_Info.
htm.
49. Connecticut Department of Public Health. Why should
you build homes with radon-resistant techniques?
Hartford, CT: Connecticut Department of Public Health
Radon Program; no date. Available from URL: http://
www.dph.state.ct.us/BRS/radon/radon_techniques.htm.
50. US Environmental Protection Agency. Radon-resistant
new construction. Washington, DC: US Environmental
Protection Agency; no date. Available from URL: http://
www.epa.gov/radon/construc.html.
51. US Environmental Protection Agency. Pesticides and child
safety. Washington, DC: US Environmental Protection
Agency; no date. Available from URL: http://www.epa.
gov/pesticides/factsheets/childsaf.htm.
52. Delaplane KS. Pesticide usage in the United States: history,
benefits, risks, and trends. Athens, GA: Cooperative
Extension Service, The University of Georgia College of
Agriculture and Environmental Sciences; no date.
Available from URL: http://pubs.caes.uga.edu/caespubs/
pubcd/B1121.htm.
53. US Environmental Protection Agency. Sources of indoor
air pollution— pesticides. Washington, DC: US
Environmental Protection Agency; no date. Available from
URL: http://www.epa.gov/iaq/pesticid.html.
54. Agency for Toxic Substances and Disease Registry. Public
health statement for asbestos. Atlanta: US Department of
Health and Human Services; 2001. Available from URL:
http://www.atsdr.cdc.gov/toxprofiles/phs61.html.
55. US Geological Survey. Some facts about asbestos. USGS
fact sheet FS-012-01, online version 1.1. Reston, VA: US
Geological Survey; March 2001. Available from URL:
http://pubs.usgs.gov/fs/fs012-01/.
56. Merriam-Webster, Inc. Merriam-Webster dictionary.
Springfield, MA: Merriam-Webster, Inc.; no date.
Available from URL: http://www.m-w.com/home.htm.
57. Jacobs DE, Clickner RP, Zhou JY, Viet SM, Marker DA,
Rogers JW, et al. The prevalence of lead-based paint
hazards in U.S. housing. Environ Health Perspect
2002;100:A599–606.
58. Centers for Disease Control and Prevention. Blood lead
levels in residents of homes with elevated lead in tap
water— District of Columbia, 2004. MMWR 2004;
53(12):268–70. Available from URL: http://www.cdc.gov/
mmwr/preview/ mmwrhtml/mm5312a6.htm.
Healthy Housing Reference Manual5-22 Chapter 5: Indoor Air Pollutants and Toxic Materials
59. National Research Council. Measuring lead exposure in
infants, children and other sensitive populations.
Washington, DC: National Academy Press; 1993.
60. Centers for Disease Control. Preventing lead poisoning in
young children. Report No. 99-2230. Atlanta: US
Department of Health and Human Services; 1991.
61. US Department of Housing and Urban Development.
HUD technical guidelines for the evaluation and control
of lead-based paint hazards in housing. Washington, DC:
US Department of Housing and Urban Development;
1995. Available from URL: http://www.hud.gov/offices/
lead/guidelines/hudguidelines/index.cfm.
62. US Department of Housing and Urban Development.
The lead-based paint disclosure rule (Section 1018 of the
Residential Lead-Based Paint Hazard Reduction Act of
1992). Washington, DC: US Department of Housing
and Urban Development; no date. Available from URL:
http://www.hud.gov/offices/lead/disclosurerule/index.cfm.
63. Residential Lead-Based Paint Hazard Reduction Act of
1992, Title X of the Housing and Community
Development Act of 1992, Pub. L. No. 102-550 (Oct 28,
1992).
64. Occupational Safety and Health Administration. Lead
exposure in construction: interim final rule. Fed Reg
1993;58:26590–649.
65. Environmental Working Group. Nationwide consumer
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arsenic on old wood. Washington, DC: Environmental
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ewg.org/reports/allhandsondeck/.
6-1Chapter 6: Housing StructureHealthy Housing Reference Manual
Chapter 6: Housing Structure
“The Palace of Fine Arts in Mexico City has sunk more than
10 feet into the ground since it was built 60 years ago and
the most noticeable effect is that the grand stone stairway has
disappeared and the entrance is now at street level.”
C.B. Crawford,
Canadian Building Digest
Introduction
The principal function of a house is to provide protection
from the elements. Our present society, however, requires
that a home provide not only shelter, but also privacy,
safety, and reasonable protection of our physical and
mental health. A living facility that fails to offer these
essentials through adequately designed and properly
maintained interiors and exteriors cannot be termed
“healthful housing.”
In this chapter, the home is considered in terms of the
parts that have a bearing on its soundness, state of repair,
and safety. These are some of the elements that the housing inspector must examine when making a thorough
housing inspection.
Figure 6.1 shows a typical house being built and
inspected today and includes a terminology key. Both the
Figure 6.1. Housing Structure Terminology, Typical House Being Built Today [1]
figure and the key are available in an interactive format in
the glossary on the U.S. Inspect Web site [1].
Figure 6.2 shows a typical house built between 1950 and
1980 and also includes a terminology key. The figures
show the complexity and the numerous components of a
home. These components form the vocabulary that is
necessary to discuss housing structure inspection issues.
Key to Figure 6.1 (New Housing Terminology)
1. Ash dump (see 35)— A door or opening in the firebox
that leads directly to the ash pit, through which the ashes
are swept after the fire is burned out. All fireboxes are not
equipped with an ash dump.
2. Attic space— The open space within the attic area.
3. Backfill— The material used to refill an excavation around
the outside of a foundation wall or pipe trench.
4. Baluster— One of a series of small pillars that is attached
to and runs between the stairs and the handrails. The
spacing between the balusters should be less than 4 inches
to prevent small children from getting stuck between the
balusters. Balusters are considered a safety item and
provide an additional barrier.
Healthy Housing Reference Manual6-2 Chapter 6: Housing Structure
5. Baseboard trim— Typically a wood trim board that is
placed against the wall around the perimeter of a room
next to the floor. The intent is to conceal the joint
between the floor and wall finish.
6. Basement window— A window opening installed in the
basement wall. Basement windows are occasionally below
the finish grade level and will be surrounded on the
exterior by a window well.
7. Blind or shutter— A lightweight frame in the form of a
door located on each side of a window. They are most
commonly constructed of wood (solid or louvered panels)
or plastic. Originally they were designed to close and
secure over the windows for security and foul weather.
Most shutters now are more likely decorative pieces that
are secured to the house beside the windows.
8. Bridging— Small pieces of wood or metal strapping
placed in an X-pattern between the floor joists at midspan
to prevent the joists from twisting and squeaking and to
provide reinforcement and distribution of stress.
9. Building paper/underlayment— Building material,
usually a felt paper that is used as a protective barrier
against air and moisture passage from the area beneath the
flooring as well as providing a movement/noise isolator in
hardwood flooring.
10. Ceiling joist— A horizontally placed framing members at
the ceiling of the top-most living space of a house that
provides a platform to which the finished ceiling material
can be attached.
11. Chair rail (not shown)— Decorative trim applied around
the perimeter of a room such as a formal dining room or
kitchen/breakfast nook at the approximate same height as
the back of a chair. It is sometimes used as a cap trim for
wainscoting (see wainscoting).
12. Chimney— A masonry or in more modern construction
wood framed enclosure that surrounds and contains one
or more flues and extends above the roofline.
13. Chimney cap— The metal or masonry protective
coveringat the top of the chimney that seals the chimney
shaft from water entry between the chimney enclosure and
the flue tiles.
14. Chimney flues— The space or channel in a chimney that
carries off the smoke and other combustion gases to the
outside air. Most homes will have a terra cotta tile flue or a
metal flue.
15. Collar beam/tie— A horizontal piece of framing lumber
that provides intermediate support for opposite rafters.
They are usually located in the middle to upper third
portion of the rafters. It is also known as a collar beam or
collar brace.
16. Concrete slab floor— Typically approximately 4 inches
thick, the concrete slab floor provides a number of uses. It
creates a solid level surface to walk and work on. It
provides a separation between the grade/soil and a
potentially livable area. It also provides lateral compression
resistance for the foundation walls, preventing soil pressure
from outside the foundation from pushing the foundation
walls and footings inward.
17. Corner brace— Diagonal braces placed at the corners of
framed walls to stiffen them and provide extra strength.
18. Cornice— An overhang of a pitched roof at the eave line
that usually consists of a fascia board, a soffit, and any
appropriate moldings or vents.
19. Cornice molding— The individual pieces of wood trim
that are applied to the cornice area at the eaves.
20. Door casing/trim— The finish trim details around the
perimeter of the door on the interior finished wall.
21. Door frame/jamb— The top and sides of the door to
include the wall framing as well as the actual door frame
and trim.
22. Downspout— A pipe, usually of metal or vinyl, that is
connected to the gutters and is used to carry the
roof-water runoff down and away from the house.
23. Downspout gooseneck— Segmented section of
downspout that is bent at a radius to allow the downspout
to be attached to the house and to follow the bends and
curves of the eaves and ground.
24. Downspout shoe— The bottom downspout gooseneck
that directs the water from the downspout to the
extension or splash block at the grade.
25. Downspout strap— Strap used to secure the downspout
to the side of the house.
26. Drain tile— A tube or cylinder that is normally installed
around the exterior perimeter of the foundation footings
that collects and directs ground water away from the
foundation of the house. The tile can be individual
sections of clay or asphalt tubing or, in more recent
construction, a perforated-plastic drain tile that is
approximately 4 inches in diameter. The drain tile leads
either towards a sump or to an exterior discharge away
from the house.
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27. Entrance canopy— A small overhanging roof that shelters
the front entrance.
28. Entrance stoop— An elevated platform constructed of
wood framing or masonry at the front entry that allows
visitors to stand above or out of the elements. The
platform should be wide enough to allow someone to
stand on the platform while opening an outward swinging
door such as a storm door even if one is not present.
29. Exterior siding— The decorative exterior finish on a
house. Its primary function is to protect the shell of the
house from the elements. The choice of siding materials
varies widely to include wood, brick, metal, vinyl,
concrete, stucco, and a variety of manufactured
compositions such as compressed wood, compressed
cellulose (paper), fiber-reinforced cement, and synthetic
stucco.
30. Fascia— The visible flat front board that caps the rafter
tail ends and encloses the overhang under the eave that
runs along the roof edge. The gutter is usually attached at
this location.
31. Fascia/rake board— The visible flat front board that caps
the rafter tail ends and encloses the overhang under the
eave that runs along the roof edge and at the edge of the
roofing at the gables. The gutter is usually attached to this
board at the eaves.
32. Finish flooring (not shown)— The final floor covering
inside the living space of a house. The most common
types of finishes are carpeting; hardwood flooring; ceramic,
composite, or laminate stone tile; parquet panels; or vinyl
sheet flooring.
33. Finished grade line— A predetermined line indicating the
proposed elevation of the ground surface around a
building.
34. Firebox— The cavity in the open face of the fireplace in
which the fire is maintained. The firebox leads directly to
the fireplace flue. The firebox is constructed of fire or
refractory brick set in fireclay or reinforced mortar in
traditional masonry fireplaces. The firebox may also be
constructed of metal or ceramic-coated metal panels in
more modern prefabricated fireplaces. The walls of the
firebox are usually slanted toward the living space both to
direct smoke up toward the flue and to reflect heat into
the room.
35. Fireplace cleanout door— The access door to the ash pit
beneath the fireplace. On a fireplace that is located inside
the house, the cleanout door is usually located in the
lowest accessible level of the house such as the basement or
crawl space. On a fireplace that is located at the outside of
the house, the cleanout door will be located at the exterior
of the chimney. Not all fireplaces are equipped with a
cleanout door.
36. Fireplace hearth— The inner or outer floor of a fireplace,
usually made of brick, tile, or stone.
37. Flashing (not shown)— The building component used to
connect and cover portions of a deck, roof, or siding
material to another surface such as a wall, a chimney, a
vent pipe, or anywhere that runoff is heavy or where two
dissimilar materials meet. The flashing is mainly intended
to prevent water entry and is usually made of rubber, tar,
asphalt, or various metals.
38. Floor joists— The main subfloor framing members that
support the floor span. Joists are usually made of
engineered wood I-beams or 2×8 or larger lumber.
39. Foundation footing— The base on which the foundation
walls rests. The foundation is wider than the foundation
wall to spread out the load it is bearing and to help
prevent settling.
40. Foundation wall— The concrete block, concrete slab or
other nonwood material that extends below or partly
below grade, which provides support for exterior walls and
other structural pans of the building.
41. Framing studs— A 2×4 or 2×6 vertical framing member
used to construct walls and partitions, usually spaced 12 to
24 inches apart.
42. Gable framing— The vertical and horizontal framing
members that make up and support the end of a building
as distinguished from the front or rear side. A gable is the
triangular end of an exterior wall above the eaves.
43. Garage door— The door for the vehicle passage into the
garage area. Typical garage doors consist of multiple
jointed panels of wood, metal, or fiberglass.
44. Girder— A large beam supporting floor joists at the same
level as the sills. A larger or principal beam used to support
concentrated loads at isolated points along its length.
45. Gravel fill— A bed of coarse rock fragments or pebbles
that is laid atop the existing soil before pouring the
concrete slab. The gravel serves a dual purpose of breaking
surface tension on the concrete slab and providing a layer
that interrupts capillary action of subsurface moisture from
reaching the concrete slab. Typically, a polyethylene
sheeting will be installed between the gravel fill and the
concrete slab for further moisture proofing.
Healthy Housing Reference Manual6-4 Chapter 6: Housing Structure
46. Gutter— A channel used for carrying water run-off.
Usually located at the eaves of a house and connected to a
downspout. The primary purpose of the gutters and
downspouts is to carry roof water run-off as far away from
the house as possible.
47. Insulation— A manufactured or natural material that
resists heat flow that is installed in a house’s shell to keep
the heat in a house in the winter and the coolness in the
house in the summer. The most common form of
insulation is fiberglass, whether in batts or blown-in
material, along with cellulose, rigid foam boards,
sprayed-in foam, and rock wool.
48. Jack/king stud— The framing stud, sometimes called the
trimmer, that supports the header above a window, door,
or other opening within a bearing wall. Depending on the
size of the opening, there may be several jack studs on
either side of the opening.
49. Mantel— The ornamental or decorative facing around a
fireplace including a shelf that is attached to the breast or
backing wall above the fireplace.
50. Moisture/vapor barrier— A nonporous material, such as
plastic or polyethylene sheeting, that is used to retard the
movement of water vapor into walls and attics and prevent
condensation in them. A vapor barrier is also installed in
crawl space areas to prevent moisture vapor from entering
up through the ground.
51. Newel post— The post at the top and bottom of the
handrails and anywhere along the stair run that creates a
directional change in the handrails is called the newel post.
The newel post is securely anchored into the underlying
floor framing or the stair stringer to provide stability to the
handrails.
52. Reinforcing lath— A strip of wood or metal attached to
studs and used as a foundation for plastering, slating or
tiling. Lath has been replaced by gypsum board in most
modern construction.
53. Ridge board/beam— The board placed on edge at the
top-most point of the roof framing, into which the upper
ends of the rafters are joined or attached.
54. Roofing— The finished surface at the top of the house
that must be able to withstand the effects of the elements
(i.e., wind, rain, snow, hail, etc.). A wide variety of
materials are available, including asphalt shingles, wood
shakes, metal roofing, ceramic and concrete tiles, and slate,
with asphalt shingles making up the bulk of the material
used.
55. Roof rafters— Inclined structural framing members that
support the roof, running from the exterior wall the to the
ridge beam. Rafters directly support the roof sheathing
and create the angle or slope of the roof.
56. Roof sheathing— The material used to cover the outside
surface of the roof framing to provide lateral and rack
support to the roof, as well as to provide a nailing surface
for the roofing material. This material most commonly
consists of plywood OSB or horizontally laid wood
boards.
57. Sidewalk— A walkway that provides a direct, all-weather
approach to an entry. The sidewalk can be constructed of
poured concrete, laid stone, concrete pavers, or gravel
contained between borders or curbs.
58. Sill plate— The horizontal wood member that is
anchored to the foundation masonry to provide a nailing
surface for floors or walls built above.
59. Silt fabric— A porous fabric that acts as a barrier between
the backfilled soil (see backfill) and the gravel surrounding
the drain tile. This barrier prevents soil particles from
blocking the movement of groundwater to the drain tile.
60. Soffit/lookout block— Rake cross-bracing between the
fly rafters and end gable rafters that the soffit is nailed to.
61. Stair rail— A sturdy handhold and barrier that follows the
outside, and sometimes inside, perimeter of the stairs. The
stair rail is used to prevent falls and to provide a means of
additional support when walking up or down the stairs.
62. Stair riser— The vertical boards that close the space
between each stair tread on a set of stairs (see stair stringer
and stair tread).
63. Stair stringer— The supporting members in a set of stairs
that are cut or notched to accept the individual treads and
risers (see stair riser and stair tread).
64. Stair tread— The horizontal board in a stairway that is
walked upon (see stair riser and stair stringer).
65. Subfloor— Boards or plywood, installed over joists, on
which the finish floor rests.
66. Support post— A vertical framing member usually
designed to carry or support a beam or girder. In newer
construction a metal lally (pronounced “lolly”) column is
commonly used, as well as 4×4- or 6×6-inch wood posts.
67. Tar— Otherwise known as asphalt, tar is a very thick, dark
brown/black substance that is used as a sealant or
waterproofing agent. It is usually produced naturally by
the breakdown of animal and vegetable matter that has
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been buried and compressed deep underground. Tar is
also manufactured— a hydrocarbon by-product or residue
that is left over after the distillation of petroleum. It is
commonly used as a sealant or patch for roof penetrations,
such as plumbing vents and chimney flashing. Tar is also
used as a sealer on concrete and masonry foundation walls
before they have been backfilled.
68. Termite shield— A metal flashing that is installed below
the sill plate that acts as a deterrent to keep termites from
reaching the sill plate.
69. Top plate— The topmost horizontal framing members of
a framed wall. Most construction practices require the top
plate to be doubled in thickness.
70. Wainscoting— The wooden paneling of the lower part of
an interior wall up to approximately waist-height or
between 36 and 48 inches from the floor.
71. Wall insulation— A manufactured or natural material
that resists heat flow that is installed in a house’s shell to
keep the heat in a house in the winter and the coolness in
the house in the summer. Fiberglass batts are the most
common form of wall insulation.
72. Wall sheathing— The material used to cover the outside
surface of the wall framing that provides lateral and shear
support to the wall as well as a nailing surface for the
exterior siding.
73. Window casing/trim— The finish trim details around
the perimeter of the window on the interior finished wall.
74. Window cripple— Short studs placed between the header
and a top plate or between a sill and sole plate.
75. Window frame/jamb— The top and sides of the
window, to include the wall framing and the actual
window frame and trim.
76. Window header— A beam placed perpendicular to wall
studs above doors, windows, or other openings to carry
the weight of structural loads above the window or door.
77. Window sash— The framework that holds the glass in a
door or window.
78. Window well (not shown)— An excavation around a
basement window that prevents the surrounding soils
from collapsing into the window. The window well
surround is normally constructed of formed corrugated
galvanized metal, built-up masonry, or pressure-treated
wood.
Figure 6.2. Housing Structure and Terminology, Typical House Built Between 1950 and 1980 [2]
Healthy Housing Reference Manual6-6 Chapter 6: Housing Structure
Key to Figure 6.2 (Old Housing Terminology)
Fireplace
1. Chimney— A vertical masonry shaft of reinforced
concrete or other approved noncombustible, heat resisting
material enclosing one or more flues. It removes the
products of combustion from solid, liquid or gaseous fuel.
2. Flue liner— The flue is the hole in the chimney. The
liner, made of terra cotta or metal, protects the brick from
harmful smoke gases.
3. Chimney cap— This top is generally of concrete. It
protects the brick from weather.
4. Chimney flashing— Sheet metal flashing provides a tight
joint between chimney and roof.
5. Firebrick— An ordinary brick cannot withstand the heat
of direct fire, and so special firebrick is used to line the
fireplace. In newer construction, fireplaces are constructed
of prefabricated metal inserts.
6. Ash dump— A trap door to let the ashes drop to a pit
below, where they may be easily removed.
7. Cleanout door— The door to the ash pit or the bottom
of a chimney through which the chimney can be cleaned.
8. Chimney breast— The inside face or front of a fireplace
chimney.
9. Hearth— The floor of a fireplace that extends into the
room for safety purposes.
Roof
10. Ridge— The top intersection of two opposite adjoining
roof surfaces.
11. Ridge board— The board that follows along under the
ridge.
12. Roof rafters— The structural members that support the
roof.
13. Collar beam— Not a beam at all; this tie keeps the roof
from spreading and connects similar rafters on opposite
sides of the roof.
14. Roof insulation— An insulating material (usually rock
wool or fiberglass) in a blanket form placed between the
roof rafters to keep a house warm in the winter and cool
in the summer.
15. Roof sheathing— The boards that provide the base for
the finished roof. In newer construction, roof sheathing is
composed of sheets of plywood, or oriented strand board
(OSB).
16. Roofing— The wood, asphalt or asbestos shingles— or
tile, slate, or metal— that form the outer protection
against the weather.
17. Cornice— A decorative element made of molded
members, usually placed at or near the top of an exterior
or interior wall.
18. Gutter— The trough that gathers rainwater from a roof.
19. Downspout— The pipe that leads the water down from
the gutter.
20. Storm sewer tile— The underground pipe that receives
the water from the downspouts and carries it to the sewer.
In newer construction, plastic-type material have replaced
tile.
21. Gable— The triangular end of a building with a sloping
roof.
22. Barage board— The fascia or board at the gable just
under the edge of the roof.
23. Louvers— A series of slanted slots arranged to keep out
rain, yet allow ventilation.
Walls and Floors
24. Corner post— The vertical member at the corner of the
frame, made up to receive inner and outer covering
materials.
25. Studs— The vertical wood members of the house, usually
2×4s at minimum and spaced every 16 inches.
26. Sill— The board that is laid first on the foundation, and
on which the frame rests.
27. Plate— The board laid across the top ends of the studs to
hold them even and tight.
28. Corner bracing— Diagonal strips to keep the frame
square and plumb.
29. Sheathing— The first layer of outer wall covering nailed
to the studs.
30. Joist— The structural members or beams that hold up the
floor or ceiling, usually 2×10s or 2×12s spaced
16 inches apart.
31. Bridging— Cross-bridging or solid. Members at the
middle or third points of joist spans to brace one to the
next and to prevent them from twisting.
32. Subflooring— Typically plywood or particle wood that is
laid over the joists.
33. Flooring paper— A felt paper laid on the rough floor to
stop air infiltration and, to some extent, noise.
6-7Chapter 6: Housing StructureHealthy Housing Reference Manual
34. Finish flooring— Hardwood, of tongued and grooved
strips, carpet, or vinyl products (tile, linoleum).
35. Building paper or sheathing— Paper or plasticized
material placed outside the sheathing, not as a vapor
barrier, but to prevent water and air from leaking in.
Building paper is also used as a tarred felt under shingles
or siding to keep out moisture or wind.
36. Beveled siding— Sometimes called clapboards, with a
thick butt and a thin upper edge lapped to shed water. In
newer construction, vinyl, aluminum, or fiber cement
siding and stucco are more prevalent.
37. Wall insulation— A blanket of wool or reflective foil
placed inside the walls.
38. Metal lath— A mesh made from sheet metal onto which
plaster or other composite surfacing materials can be
applied. In newer construction, plaster sheetrock 4-×8-foot
sheets have replaced lath.
Foundation and Basement
39. Finished grade line— The top of the ground at the
foundation.
40. Foundation wall— The wall of poured concrete (shown)
or concrete blocks that rests on the footing and supports
the remainder of the house.
41. Termite shield— A metal baffle to prevent termites from
entering the frame.
42. Footing— The concrete pad that carries the entire weight
of the house upon the earth.
43. Footing drain tile— A pipe with cracks at the joints, or
perforated plastic pipe to allow underground water to
drain away before it gets into the basement.
44. Basement floor slab— The 4- or 5-inch layer of concrete
that forms the basement floor.
45. Gravel fill— Placed under the slab to allow drainage and
to guard against a damp floor.
46. Girder— A main beam upon which floor joists rest.
Usually of steel, but also of wood.
47. Backfill— Earth, once dug out, that has been replaced
and tamped down around the foundation.
48. Areaway— An open space to allow light and air to a
window. Also called a light well.
49. Area wall— The wall, of metal or concrete, that forms the
open area.
Windows and Doors
50. Window— An opening in a building for admitting light
and air. It usually has a pane or panes of glass and is set in
a frame or sash that is generally movable for opening and
shutting.
51. Window frame— The lining of the window opening.
52. Window sash— The inner frame, usually movable, that
holds the glass.
53. Lintel— The structural beam over a window or door
opening.
54. Window casing— The decorative strips surrounding a
window opening on the inside.
Stairs and Entry
55. Entrance canopy— A roof extending over the entrance
door.
56. Furring— Falsework or framework necessary to bring the
outer surface level to the inner surface.
57. Stair tread— The horizontal part of a step that the foot
hits when climbing up or down the stairs.
58. Stair riser— The vertical board connecting one tread to
the next.
59. Stair stringer— The sloping board that supports the ends
of the steps.
60. Newel— The post that terminates the railing.
61. Stair rail— The bar used for a handhold when using the
stairs.
62. Balusters— Vertical rods or spindles supporting a rail.
Foundation
The word “foundation” is used to mean
• construction below grade, such as footings, cellar, or
basement;
• the composition of the earth on which the building
rests; and
• special construction, such as pilings and piers used to
support the building.
The foundation bed may be composed of solid rock, sand,
gravel, or unconsolidated sand or clay. Rock, sand, or
gravel are the most reliable foundation materials. Figure
6.3 shows the three most common foundations for homes.
Unconsolidated sand and clay, though found in many sections of the country, are not as desirable for foundations
Healthy Housing Reference Manual6-8 Chapter 6: Housing Structure
because they are subject to sliding and settling [1].
Capillary breaks have been identified as a key way of
reducing moisture incursion in new construction [3].
The footing distributes the weight of the building over a
sufficient area of ground to ensure that the foundation
walls will stand properly. Footings are usually concrete;
however, in the past, wood and stone have been used.
Some older houses were constructed without footings.
Although it is usually difficult to determine the condition
of a footing without excavating the foundation, a footing
in a state of disrepair or lack of a footing will usually be
indicated either by large cracks or by settlement in the
foundation walls. This type of crack is called a “Z” crack.
Foundation wall cracks are usually diagonal, starting from
the top, the bottom, or the end of the wall (Figure 6.4).
Figure 6.4. Foundation Cracks [4]
Figure 6.3. Foundation [3]
Cracks that do not extend
to at least one edge of the
wall may not be caused by
foundation problems. Such
wall cracks may be due to
other structural problems
and should also be reported.
The foundation walls support the weight of the structure and transfer this weight
to the footings. The foundation walls may be made
of stone, brick, concrete, or
concrete blocks. The exterior should be moisture
proofed with either a membrane of waterproof material or a coating of portland
cement mortar. The membrane may consist of plastic
sheeting or a sandwich of
standard roofing felt joined
and covered with tar or
asphalt. The purpose of
waterproofing the foundation and walls is to prevent
water from penetrating the wall material and leaving the
basement or cellar walls damp.
Holes in the foundation walls are common in many old
houses. These holes may be caused by missing bricks or
blocks. Holes and cracks in a foundation wall are undesirable because they make a convenient entry for rats and
other rodents and also indicate the possibility of further
structural deterioration. Basement problems are a major
complaint of homeowners [4–9].
Concrete is naturally porous (12%–18% air). When it
cures, surplus water creates a network of interconnected
capillaries. These pores let in liquid water, water vapor,
and radon gas. Like a sponge, concrete draws water from
several feet away. As concrete ages, the pores get bigger as
a result of freezing, thawing, and erosion.
Concrete paints, waterproofing sealers, or cement coatings are a temporary fix. They crack or peel and cannot
stop gases such as water vapor and radon.
Damp basement air spreads mold and radon through the
house. Efflorescence (white powder stains) and musty
odors are telltale signs of moisture problems.
6-9Chapter 6: Housing StructureHealthy Housing Reference Manual
potential problem, 6-mil plastic sheets should be laid as
vapor barriers over the entire crawl space floor. The sheets
should overlap each other by at least 6 inches and should
be taped in place. The plastic should extend up the
perimeter walls by about 6 inches. The plastic sheets
should be attached to the interior walls of the crawl space
with mastic or batten strips. All of the perimeter walls
should be insulated, and insulation should be between
the joists at the top of the walls. Vents, which may need
to be opened in the late spring and closed in the fall,
should not be blocked. If not properly managed, moisture originating in the crawl space can cause problems
with wood flooring and create many biologic threats to
health and property. A properly placed vapor barrier can
prevent or reduce problem moisture from entering the
home.
Vapor Barriers for Concrete Slab Homes
Strip flooring and related products should be protected
from moisture migration by a slab. Proper on-grade or
above-grade construction requires that a vapor barrier be
placed beneath the slab. Moisture tests should be done to
determine the suitability of the slab before installing
wood products. A vapor barrier equivalent to 4- or 6-mil
polyethylene should be installed on top of the slab to further protect the wood products and the residents of the
home.
Wall and Ceiling Vapor Barriers
Wall and ceiling vapor barriers should go on the heated
side of the insulation and are necessary in cold climates.
Water vapor flows from areas of high pressure (indoors in
winter) through the wall to an area of low pressure (outdoors in winter). People and their pets produce amazing
quantities of water vapor by breathing. Additional moisture in considerable quantities is created in the home
from everyday activities such as washing clothes, cooking,
and personal hygiene. The purpose of the vapor barrier is
to prevent this moisture from entering the wall and freezing, then draining, causing damage. In addition, wet
insulation has very little insulating value. Insulation with
the vapor barrier misplaced will allow the vapor to condense in the insulation and then freeze. In cold climates,
this ice can actually build up all winter and run out on
the floor in the spring. Such moisture buildup blisters
paint, rots sheathing, and destroys the insulating value of
insulation.
Basement remodeling traps invisible water vapor, causing
mold and mildew. Most basements start leaking within
10 to 15 years. The basement walls and floors should be
sealed and preserved before they deteriorate. The basement floor should be concrete placed on at least 6 inches
of gravel. The gravel distributes groundwater movement
under the concrete floor, reducing the possibility of the
water penetrating the floor. A waterproof membrane,
such as plastic sheeting, should be laid before the concrete is placed for additional protection against flooding
and the infiltration of radon and other gases.
The basement floor should be gradually, but uniformly,
sloped from all directions toward a drain or a series of
drains. These drains permit the basement or cellar to
drain if it becomes flooded.
Water or moisture marks on the floor and walls are signs
of ineffective waterproofing or moisture proofing. Cellar
doors, hatchways, and basement windows should be
weather-tight and rodent-proof. A hatchway can be
inspected by standing at the lower portion with the doors
closed; if daylight can be seen, the door needs to be
sealed or repaired.
Vapor Barriers
Crawl Space Vapor Barriers
Throughout the United States, even in desert areas, there
is moisture in the ground from groundwater being
absorbed. Even in an apparently dry crawl space, a large
amount of water is entering. The moisture is drying out
as fast as it is entering, which causes high moisture levels
in the crawl space and elsewhere in the house. A solid
vapor barrier is recommended in all crawl spaces and
should be required if moisture problems exist [10]. This
vapor barrier, if properly installed, also reduces the infiltration of radon gas. Of course, if the moisture is coming
from above ground, a vapor barrier will collect and hold
the moisture. Therefore, any source of moisture must be
found and eliminated. The source may be as obvious as
sweating pipes, or may be more difficult to spot, such as
condensation on surfaces. The solution can be as simple
as applying insulation to exposed sections of the piping or
complex enough to require power exhaust fans and the
addition of insulation and vapor barriers.
The more common causes of moisture problems in a new
home are moisture trapped within the structure during
construction and a continuing source of excess moisture
from the basement, crawl space, or slab. To resolve this
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House Framing
Many types of house-framing systems are found in
various sections of the country; however, most framing
systems include the elements described in this section.
Foundation Sills
The purpose of the sill is to provide support or a bearing
surface for the outside walls of the building. The sill is
the first part of the frame to be placed and rests directly
on the foundation wall. It is often bolted to the foundation wall by sill anchors. In many homes, metal straps are
cemented into the foundation wall that are bent around
and secured to the sill. It is good practice to protect the
sill against termites by extending the foundation wall to
at least 18 inches above the ground and using a noncorroding metal shield continuously around the outside top
of the foundation wall.
Flooring Systems
The flooring system is composed of a combination of
girders, joists, subflooring, and finished flooring that may
be made up of concrete, steel, or wood. Joists are laid perpendicular to the girders, at about 16 inches on center,
and the subflooring is attached to them. If the subfloor is
wood, it may be nailed, glued, or screwed at either right
angles or diagonally to the joists. Many homes are built
with wood I-joists or trusses rather on than solid wood
joists.
In certain framing systems, a girder supports the joists
and is usually a larger section than the joists it supports.
Girders are found in framing systems where there are no
interior bearing walls or where the span between bearing
walls is too great for the joists. The most common application of a girder is to support the first floor. Often a
board known as a ledger is applied to the side of a wood
girder or beam to form a ledge for the joists to rest upon.
The girder, in turn, is supported by wood posts or steel
“lally columns” that extend from the cellar or basement
floor to the girder.
Studs
For years, wall studs were composed of wood and were
2×4 inches; but, with the demand for greater energy efficiency in homes, that standard no longer holds true.
Frame studs up to 6 inches wide are used to increase the
area available for placing insulation material. The increased
size in the studs allow for larger spaces between joists.
There are now alternatives to conventional wood studs,
specifically, insulated concrete forms, structural insulated
panels, light-gauge steel, and combined steel and wood
[11–13]. The advantages of light-gauge steel include the
following:
• weighs 60% less than equivalent wood units and has
greater strength and durability;
• is impervious to termites and other damage-causing
pests;
• stays true and does not warp;
• is noncombustible; and
• is recyclable.
The disadvantages of steel include these:
• steel is an excellent thermal conductor and requires
additional external insulation;
• as a new product, it is unfamiliar to craftsmen,
engineers, and code officials; and
• a different type of construction tools are required.
The combined steel and wood framing system includes
light-gauge steel studs with 6-inch wooden stud pieces
attached to the top and bottom to allow easy attachment
to traditional wood frame materials.
There are two types of walls or partitions: bearing and
nonbearing. A bearing wall is constructed at right angles
to support the joists. A nonbearing wall, or partition, acts
as a screen or enclosure; hence, the headers in it are often
parallel to the joists of the floor above.
In general, studs, like joists, are spaced 16 inches on center. In light construction, such as garages and summer
cottages, wider spacing on studs is common.
Openings for windows or doors must be framed in studs.
This framing consists of horizontal members (headers)
and vertical members (trimmers or jack studs).
Because the vertical spaces between studs can act as flues
to transmit flames in the event of a fire, fire stops are
important in preventing or retarding fire from spreading
through a building by way of air passages in walls, floors,
and partitions. Fire stops are wood obstructions placed
between studs or floor joists to block fire from spreading
in these natural flue spaces.
Interior Walls
Many types of materials are used for covering interior
walls and ceilings, but the principal type is drywall. The
generic term “drywall” is typically used when talking
about gypsum board. It is also called wallboard or referred
6-11Chapter 6: Housing StructureHealthy Housing Reference Manual
to by the brand name Sheetrock. Gypsum board is a sheet
material composed of a gypsum filler faced with paper. In
drywall construction, gypsum boards are fastened to the
studs either vertically or horizontally and then painted.
The edges along the length of the sheet are slightly
recessed to receive joint cement and tape.
Drywall finish, composed of gypsum board, is a material
that requires little, if any, wait for application. Other drywall finishes include plywood, fiberboard, or wood in
various sizes and forms. Plaster was once quite popular
for interior walls. Plaster is a mixture (usually of lime,
sand, and water) applied in two or three coats to lath to
form a hard-wall surface. A plaster finish requires a base
on which plaster can be spread. Wood lath at one time
was the plaster base most commonly used, but today gypsum-board lath is more popular. Gypsum lath may be
perforated to improve the bond and thus lengthen the
time the plaster can remain intact when exposed to fire.
Building codes in some cities require that gypsum lath be
perforated. Expanded-metal lath also may be used as a
plaster base. Expanded-metal lath consists of sheet metal
slit and expanded to form openings to hold the plaster.
Plaster is applied over the base to a minimum thickness
of ½ inch. Because wood-framing members may dry after
the house is completed, some shrinkage can be expected,
which, in turn, may cause plaster cracks to develop
around openings and in corners. Strips of lath embedded
in the plaster at these locations prevent cracks. Bathrooms
have unique moisture exposure problems and local code
approved cement board should be used around bath and
shower enclosures.
Stairways
The purpose of stairway dimension standards is to ensure
adequate headroom and uniformity in riser and tread size.
Interior stairways (Figure 6.5) should be no less than 44
inches wide. The width of a stairway may be reduced to
36 inches when permitted by local or state code in oneand two-family dwellings. Stairs with closed risers should
have maximum risers of 8¼ inches and minimum treads
of 9 inches plus 1 inch nosing. Basement stairs are often
constructed with open risers. These stairs should have
maximum risers of 8¼ inches and minimum treads of 9
inches plus 1-inch nosing. The headroom in all parts of
the stair enclosure should be no less than 80 inches.
Dimensions of exterior stairways should be the same as
those of interior stairways, except that the headroom
requirement does not apply.
Staircases should have handrails that are between 1¼ and
25/8 inches wide, particularly if the staircases have more
than four steps. Handrails should be shaped so they can
be readily grasped for safety and placed so they are easily
accessible. Handrails should be 4⅛ inches from the wall
and be 34 to 38 inches above the leading edge of the
stairway treads. Handrails should not end in any manner
or have projections that can snag clothing.
Windows
The six general classifications of windows (Figure 6.6) are
as follows [1]:
• Double-hung sash windows that move up or down,
balanced by weights hung on chains, ropes, or springs
on each side;
• Casement sash windows that are hinged at the side and
can be hung so they will swing out or in;
• Awning windows that usually have two or more glass
panes that are hinged at the top and swing out
horizontally;
• Sliding windows that usually have two or more glass
panes that slide past one another on a horizontal track;
• Fixed windows that are generally for increased light
entry and decorative effect; and
• Skylight windows for increased room illumination and
decoration that can be built to open.
Figure 6.5. Interior Stairway [4]
Healthy Housing Reference Manual6-12 Chapter 6: Housing Structure
The principal parts of a
window, shown in threedimensional view in
Figure 6.7 and face-on and
side view in Figure 6.8, are
the following:
Drip cap— A separate
piece of wood projecting
over the top of the window; a component of the
window casing. The drip
cap protects against
moisture.
Window trough— The
cut or groove in which the
sash of the window slides
or rests.
Window sill— The shelf
on the bottom edge of a
window, either a projecting part of the window
frame or the bottom of
the wall recess that the
window fits into. The sill
contains the trough and
protects against moisture.
Recent technological advancements— new materials,
coatings, design, and construction features— make it possible to choose windows that allow you to balance winter
heating and summer cooling needs without sacrificing
versatility or style. To ensure that windows, doors, or skylights selected are appropriate for the region in which
they are to be installed, Energy Star Certification labels
include a climate region map.
Some window glass is made of tempered glass to resist
breakage. Some windows are made of laminated glass,
which resists breakage, but if broken produces glass
shards too small to cause injury [14]. The glazing, or
glass, can be a solid glass sheet (single glazed) or have two
layers of glass (double glazed) separated by a spacer. Air
trapped between the glass layers provides some insulation
value. Triple-glazed windows have three pieces of glass, or
two layers of glass with a low emissivity film suspended
between them. Triple-glazed windows have advantages
where extremes in weather and temperature are the norm.
They also can reduce sound transmission to a greater
degree than can single- or double-glazed windows.
Figure 6.8. Window Details [3]
Figure 6.6. Classifications of Windows [1]
Figure 6.7. Three Dimensional View of a Window [1]
6-13Chapter 6: Housing StructureHealthy Housing Reference Manual
becomes difficult to lift and lower. This may be something that can be resolved with simple adjustments, or it
may be more serious. If the door is connected to an electric opener, the opener mechanism can be disconnected
from the door by pulling the release cord or lever. If the
door then works manually, the problem is with the electric opener. A door that seems unusually hard to lift may
have a problem with spring tension. Wood doors should
be properly painted or stained both outside and inside. If
only the outside of a garage door is finished, the door
may warp and moisture may cause the paint to peel.
Rules issued by the Consumer Product Safety
Commission on December 3, 1992, specify entrapment
protection requirements for garage doors [15].
The rules require that residential garage door openers
contain one of the following:
• An external entrapment protection device, such as an
electric eye that sees an object obstructing the door
without having actual contact with the object. A
door-edge sensor is a similar device. The door-edge
sensor acts much like the door-edge sensors on elevator
doors.
• A constant contact control button, which is a
wall-mounted button requiring a person to hold in the
control button continuously for the door to close
completely. If the button is released before the door
closes, the door reverses and opens to the highest
position.
• A sticker on all newly manufactured garage door
openers warning consumers of the potential entrapment
hazard. The sticker is to be placed near the
wall-mounted control button.
The variety of exterior door systems has increased significantly over the past 5 to 10 years. Many combine several
different materials to make a realistic, if not actual wood,
door that provides both beauty and enhanced security.
Exterior House Doors
Exterior door frames are ordinarily of softwood plank,
with the side rabbitted to receive the door in the same
way as casement windows. At the foot is a sill, made of
hardwood or other material, such as aluminum, to withstand the wear of traffic and sloped down and out to shed
water. Doors often come equipped with door sweeps to
conserve energy.
The four primary categories of modern exterior doors are
steel, fiberglass, composites, and wood.
Doors
There are many styles of doors both for exterior and interior use. Exterior doors must, in addition to offering privacy, protect the interior of the structure from the
elements. Various parts of a door are the same as the corresponding parts of a window. A door’s function is best
determined by the material from which it is made, how it
looks, and how it operates. When doors are used for security, they are typically made from heavy materials and
have durable, effective locks and hinges. A door that lets
in light or allows people to look out onto the yard, such
as a sliding glass door or a french door, will have multiple
panes (also called lights) or be made almost completely of
glass.
Houses have many exterior and interior door options.
Exterior doors are typically far sturdier than interior
doors and need to be weather tight and ensure security
for the home. Exterior doors are also more decorative
than most interior doors and may cost a considerable
amount. Typical exterior doors include front entry doors,
back doors, french doors, dutch doors, sliding glass doors,
patio doors, and garage doors.
French doors and sliding doors are examples of the two
primary ways doors open. French doors swing on hinges;
sliding doors glide along a track. Some doors, such as
dutch doors, have tops and bottoms that swing open
independently.
Most doors are made of wood or materials made to look
like wood. Fiberglass composite and steel doors often
have polymer or vinyl coatings embossed with wood
grain; some even have cellulose-based coatings that can be
stained like wood doors. Wood doors are made from
every kind of wood imaginable, hardwoods being the
most durable and elegant. Wood doors insulate better
than glass; composite and steel doors provide even more
insulation and durability, as well as better security than
does wood.
Garage Doors
Garage doors open in almost any configuration needed
for the design of the home. Installing most garage doors
is complex and dangerous enough that only a building
professional should attempt it. Garage doors often
include very strong springs that can come loose and
severely injure the unsuspecting installer. Garage door
springs are under extreme tension because of the heavy
loads they must lift, which makes them dangerous to
adjust. A garage door may suffer from any of several
problems. The most common problem is that the door
Healthy Housing Reference Manual6-14 Chapter 6: Housing Structure
Steel— The most common exterior door sold today is
steel. Humidity will not cause a steel door to warp or
twist. Steel doors often have synthetic wood-grain
embossed finishes that accept stain. Just about every steel
exterior door is filled with some type of foam. This foam
allows the doors to achieve R-values almost five times
that of an ordinary wood door. Metal is often used as a
veneer frame. In general, the horizontal members are
called rails and the vertical members are called stiles.
Every door has a top and bottom rail, and some may have
intermediate rails. There are always at least two stiles, one
on each side of the door.
Fiberglass— The second most frequently selected exterior
door is fiberglass. Fiberglass doors are similar to steel
doors, but tend to be much more resistant to denting.
(Steel doors can be dented quite easily.) Fiberglass doors
also are stainable and have rich, realistic wood graining.
Fiberglass doors are insulated with foam and have high
R-values.
Composite materials— The third most common exterior
door is made of composite materials. These doors often
are of two materials blended together. Their composite
fiber-reinforced core can be twice as strong as wood. This
composite core will not rot, warp, or twist when subjected to high levels of humidity.
Wood— The last major category of doors is wood. Solid
wood doors range from inexpensive to true works of art.
Their downside is that they can warp and bow if not
sealed properly from humidity and will then fit poorly in
their frames.
Other types of wooden doors are described below.
• Batten doors are often found on older homes. They
are made of boards nailed together in various ways.
The simplest is two layers nailed to each other at right
angles, usually with each layer at 45° to the vertical.
Another type of batten door consists of vertical boards
nailed at right angles to several (two to four) cross
strips called ledgers, with diagonal bracing members
nailed between the ledgers. If vertical members
corresponding to ledgers are added at the sides, the
verticals are called frames. Batten doors are often
found in cellars and other places where appearance is
not a factor and economy is desired.
• Solid flush doors are perfectly flat, usually on both
sides, although occasionally they are made flush on
one side and are paneled on the other. Flush doors
sometimes are solid planking, but they are commonly
veneered and possess a core of small pieces of white
pine or other wood. These pieces are glued together
with staggered end joints. Along the sides, top, and
bottom are glued ¾ inch edge strips of the same
wood, used to create a smooth surface that can be cut
or planed. The front and back faces are then covered
with a ⅛-inch to ¼-inch layer of veneer. Solid flush
doors may be used on both the interior and exterior.
• Hollow-core doors, like solid flush doors, are
perfectly flat; but, unlike solid doors, the core consists
mainly of a grid of crossed wooden slats or some other
type of grid construction. Faces are three-ply plywood
instead of one or two plies of veneer, and the surface
veneer may be any species of wood, usually hardwood.
The edges of the core are solid wood and are made
wide enough at the appropriate places to accommodate
locks and butts. Doors of this kind are considerably
lighter than solid flush doors. Hollow-core doors are
usually used as interior doors.
Many doors are paneled, with most panels consisting of
solid wood or plywood, either raised or flat, although
exterior doors frequently have one or more panels of
glass. One or more panels may be used, although some
have as many as nine panels. Paneled doors may be used
both on the interior or exterior.
The frame of a doorway is the portion to which the door
is hinged. It consists of two side jambs and a head jamb,
with an integral or attached stop against which the door
closes.
Roof Framing
Rafters
One of a series of structural roof members spanning from
an exterior beam or a ridge board. Rafters serve the same
purpose for the roof as joists do for floors, that is, providing support for sheathing and roofing material. They are
typically placed on 16-inch centers.
Collar Beam
Collar beams are ties between rafters on opposite sides of
the roof. If the attic is to be used for rooms, the collar
beam may double as the ceiling joist.
Purlin
A purlin is the horizontal member that forms the support
for the rafters at the intersection of the two slopes of a
gambrel roof.
6-15Chapter 6: Housing StructureHealthy Housing Reference Manual
Ridge Board
A ridge board is a horizontal member that forms a lateral
tie to make rafters secure.
Hip
A hip is like a ridge, except that it slopes. It is the intersection of two adjacent, rather than two opposite, roof planes.
Roof Sheathing
The manner in which roof sheathing is applied depends
upon the type of roofing material. Roof boards may vary
from tongue-and-groove lumber to plywood panels.
Dormer
The term “dormer window” is applied to all windows in
the roof of a building, whatever their size or shape.
Roofs
Asphalt Shingle
The principal damage to asphalt shingle roofs is caused
by strong winds on shingles nailed close to the ridge line
of the roof. Usually the shingles affected by winds are
those in the four or five courses nearest the ridge and in
the area extending about 5 feet down from the edge or
rake of the roof.
EPDM
Ethylene propylene diene monomer (EPDM) is a singleply roofing system. EPDM allows extreme structural
movement without splitting or cracking and retains its
pliability in a wide range of temperatures.
Asphalt Built-up Roofs
Asphalt roofs may be unsurfaced (a coating of bitumen
being exposed directly to the weather) or surfaced (with
slag or gravel embedded in the bituminous coating).
Using surfacing material is desirable as a protection
against wind damage and the elements. This type of roof
should have enough pitch to drain water readily.
Coal Tar Pitch Built-up Roofs
This type of roof must be surfaced with slag or gravel. A
coal tar pitch built-up roof should always be used on a
deck pitched less than ½ inch per foot; that is, where
water may collect and stand. This type of roof should be
inspected on completion, 6 months later, and then at
least once a year, preferably in the fall. When the top
coating of bitumen shows damage or has become badly
weathered, it should be renewed.
Slate Roofs
The most common problem with slate roofs is the
replacement of broken slates. Otherwise, slate roofs normally render long service with little or no repair.
Tile Roofs
Replacement of broken shingle tiles is the main maintenance problem with tile roofs. This is one of the most
expensive roofing materials. It requires very little maintenance and gives long service.
Copper Roofs
Usually made of 16-ounce copper sheeting and applied to
permanent structures, copper roofs require practically no
maintenance or repair when properly installed. Proper
installation allows for expansion and contraction with
changes in temperature.
Galvanized Iron Roofs
The principal maintenance for galvanized iron roofs
involves removing rust and keeping the roof well painted.
Leaks can be corrected by renailing, caulking, or replacing
all or part of the sheet or sheets in disrepair.
Wood Shingle Roofs
The most important factors of wood shingle roofs are
their high pitch and exposure, the character of wood, the
kind of nails used and the preservative treatment given
the shingles. At one time these roofs were treated with
creosote and coal tar preservatives. Because they are made
from a flammable material, insurance companies frequently have higher rates for wood shingle roofs.
Roof Flashing
Valleys in roofs (such as gambrel roofs, which have two
pitches designed to provide more space on upper floors
and are steeper on their lower slope and flatter toward the
ridge) that are formed by the junction of two downward
slopes may be open or closed. In a closed valley, the
slates, tiles, or shingles of one side meet those of the
other, and the flashing below them may be comparatively
narrow. In an open valley, the flashing, which may be
made of zinc, copper, or aluminum, is laid in a continuous strip, extending 12 to 18 inches on each side of the
valley, while the tiles or slates do not come within 4 to 6
inches of it. The ridges built up on a sloping roof where
it runs down against a vertical projection, like a chimney
or a skylight, should be weatherproofed with flashing.
Failure of roof flashing is usually due to exposed nails
that have come loose. The loose nails allow the flashing
Healthy Housing Reference Manual6-16 Chapter 6: Housing Structure
to lift, resulting in leakage. Flashings made of lead or
coated with lead should not be used.
The use of a thin, self-sticking rubber ice and water
shield under flashings and on the edge of roofs is now
common practice. The shield helps reduce leakage and
ice backup in cold climates, preventing serious damage
to this part of the home.
Gutters and Leaders
Gutters and leaders should be of noncombustible materials and should not be made of lead, lead-coated copper,
or any other formulation containing lead. They should
be securely fastened to the structure and spill into a
storm sewer, not a sanitary sewer, if the neighborhood
has one. When there is no storm sewer, a concrete or
stone block placed on the ground beneath the leader
prevents water from eroding the lawn. This stone block
is called a splash block. Gutters should be checked every
spring and fall and cleaned when necessary. Gutters must
be placed or installed to ensure that water drainage is
taken away from the foundation of the house. Soil
around the home should be graded in a manner that also
drains the water away from the foundation of the home.
Exterior Walls
and Trim
Exterior walls are enclosure walls whose purpose
is not only to make the
building weather tight,
but to also allow the
building to dry out. In
most one- to three-story
buildings they also serve
as bearing walls. These
walls may be made of
many different materials
(Figure 6.9).
Brick is often used to
cover framed exterior
walls. In this situation,
the brick is only one
course thick and is called
a brick veneer. It supports nothing but itself
and is kept from toppling by ties connected
to the frame wall.
In frame construction, the base material of the exterior
walls is called sheathing. The sheathing material may be
square-edge, shiplap, tongue-and-groove boards, or plywood or oriented strand board (OSB). Sheathing, in
addition to serving as a base for the finished siding material, stiffens the frame to resist sway caused by wind. It is
for this reason that sheathing is applied diagonally on
frame buildings. Its role is to brace the walls effectively
to keep them from racking.
Many types of sidings, shingles, and other exterior coverings are applied over the sheathing. Vinyl siding; wood
siding; brick, cedar, and other wood shingles or shakes;
asphalt; concrete; clapboard; common siding (called
bevel siding); composition siding; cement shingles; fiber
cement (e.g., Hardiplank); and aluminum siding are
commonly used for exterior coverings. In older homes,
asbestos-cement siding shingles can still be found as an
exterior application or underneath various types of aluminum or vinyl siding.
Clapboard and common siding differ only in the length
of the pieces. Composition siding is made of felt, grit,
and asphalt, which are often shaped to look like brick.
Asbestos and cement shingles, which were used until the
early 1970s, are rigid and produce a siding that is fireresistant, but also a health hazard. Cedar wood shingles
and aluminum are manufactured with a backer board
that gives insulation and fire-resistant qualities. Vinyl
siding is manufactured from polyvinyl chloride (PVC),
a building material that has replaced metal as the prime
material for many industrial, commercial, and consumer
products. PVC has many years of performance as a construction material, providing impact-resistance, rigidity,
and strength. The use of vinyl siding is not without controversy, because PVC is known to cause cancer in
humans. Accidental fires in vinyl-sided buildings are
more dangerous because vinyl produces toxic vapors
when heated.
Putting It All Together
The next section shows a home being built by Habitat
for Humanity.
This small, one-family home represents all of the processes that would also be used for a far more expensive
and elaborate dwelling. The homebuilding demonstrated
by the following pictures was by an industrial arts class
to educate and train a new generation of construction
specialists and homebuilders.
Figure 6.9. Wall Framing [4]
6-17Chapter 6: Housing StructureHealthy Housing Reference Manual
A.
The foundation trench for a new home has horizontal
metal rods, also called reinforcement rods or rebar, to
increase the strength of the concrete. After the concrete
hardens, a perforated pipe 4 to 6 inches in diameter is
placed beside it to collect water and allow it to drain
away from the foundation. This pipe is the footing
drain, and the poured concrete beside it is the footer.
The footing drain is important in removing water from
the base of the home. It also serves the secondary
purpose of moisture control in the home and provides a
venting route for radon gas. The holes dug near the legs
of the workers will be filled with concrete and form the
footer that will hold up the porch of the home.
To assist in preventing capillary action from wicking
water from the foundation to the wooden structure,
a polyethylene sheet is placed over the footer before
pouring the concrete foundation, or building a
cinderblock foundation.
B.
The concrete on top of the footer is leveled to establish
a surface for the foundation of the home. Once the
footer has hardened, the perforated drainage pipe will
be laid on the outside of the poured foundation wall.
The reinforcing rods were positioned in the trench
before pouring the concrete.
C.
Concrete will be poured into this form on top of the
footer to create the foundation of the home. Again,
reinforcing rods are added to ensure that the concrete
has both lateral strength, as well as the strength to
support the home. Once the concrete has hardened
and becomes seasoned, the forms will be removed to
reveal the finished poured concrete foundation over
the perforated drainage pipe. Not shown is a newer
technique of using insulating polystyrene forms and ties
in a building foundation.
Healthy Housing Reference Manual6-18 Chapter 6: Housing Structure
E.
Gravel fill is placed outside the finished poured concrete
foundation. This ensures that moisture does not stand
around the foundation for any time. The moisture is
routed to the footing drain for fast dispersal.
F.
A termite shield is established on top of the concrete
wall (foundation) just below the sill of the home. The
sill is typically made of pressure- and insecticide-treated
wood to ensure stability and long life.
A cinderblock foundation will be used to support the
storage shed attached to the house. Note the potential
for inadvertent sabotage of the termite shield if a
shield is not installed on the top of the cinder block
foundation.
G.
OSB subfloor, the joist supporting the floor, and the
metal bridging that is used to keep the joist from
twisting can be seen from the crawl space under the
home.
If the material used for the flooring or external
sheathing of the home is made of plywood or a
composition that is not waterproof, the material must
be protected from rain to prevent deterioration and
germination of mold spores. Some glues or resins
release toxic vapors for years if deterioration is allowed
to begin.
D.
Foundations are not always poured concrete, but are
often cinderblock or similar materials that are cemented
in place to form the load-bearing wall. The arrow
shows the concrete chute delivering concrete into the
form. Long poles are pushed into the freshly poured
concrete to remove air pockets that would weaken the
foundation.
Care must be taken to ensure that the forms are
appropriately supported before pouring the concrete.
Often tar, plastic, or other waterproof materials are
placed on the outside of the foundation to the ground
level to further divert moisture from the house to the
footing drains.
6-19Chapter 6: Housing StructureHealthy Housing Reference Manual
H.
The flooring material of the first floor of the home is
OSB applied to the subfloor with both glue and wood
screws. Where possible, the screws should extend into
the subfloor and the joist below the subfloor to prevent
squeaking.
J.
The exterior wall framing is composed of studs that
are 2x6-inch boards. The horizontal member extending
from one exterior wall to the other is called a girder
and is a prime support for the second floor of the home.
The larger studs in the exterior wall are used both for
greater strength and to provide greater energy efficiency
for the home.
The lintels above the windows and doors distribute the
weight of the second floor and roof across the studs
that are located on each side of the openings in the
frame.
K.
The joists above the first floor are connected to the
central girder of the home by steel brackets. These
brackets provide a far more effective alternative than
does toenailing nails to hold the joists in place or to
notching the girder to hold them.
I.
The interior wall framing is composed of studs
traditionally referred to as 2×4s. The horizontal member
at the top of the studs is called a girt or a ribbon. In
this case the builders have used two 2×4s, placing
one on top of the other. Because the outside walls
have used studs that are 2×6-inch boards, the girts
or ribbons on top of these are also double 2×6-inch
boards.
Healthy Housing Reference Manual6-20 Chapter 6: Housing Structure
L.
The subroof or roof sheathing is applied from the
bottom up with temporary traction boards nailed to the
subroof to allow safe installation of the material.
The subroof is placed on the rafters up to the ridge
board of the roof. A waterproof material will be added to
the subroof before installing the final roofing material.
M.
An interior wall is installed to create second-floor
rooms.
The subroof has been installed.
The exterior wood of the home has been covered with
plastic sheathing or a housewrap to protect it from
moisture.
N.
Flashing material, such as sheet metal, is installed at
critical locations to make sure that water does not enter
the home where the joints and angles of a roof meet:
where the dormer roof meets the roof and the walls of
the dormer meet the roof, where windows penetrate the
walls, where the vent stack penetrates the roof, where
the porch roof meets the front wall, skylights, and eaves
of the house.
O.
A safety scaffold is standing at the rear of the home,
and the final roofing material has been applied, in
addition to the exterior vinyl siding.
6-21Chapter 6: Housing StructureHealthy Housing Reference Manual
References
1. US Inspect. Glossary of terms. Chantilly, VA: US Inspect;
no date. Available from URL: http://www.usinspect.com/
Glossary/glossary.asp.
2. Center for Disease Control. Housing construction
terminology. In: Basic housing inspection. Atlanta: US
Department of Health and Human Services; 1976.
3. Building Science Corporation. Read this before you
design, build, or renovate. Westford, MA: Building
Science Corporation; 2004.
4. Center for Disease Control. Basic housing inspection.
Atlanta: US Department of Health and Human Services;
1976.
5. Wagner JD. Drying out a wet basement. New York: This
Old House Ventures, Inc.; no date. Available from URL:
http://www.thisoldhouse.com/toh/knowhow/interiors/
article/0,16417,220912,00.html.
6. Friedman D. Inspecting foundations for structural defects.
Poughkeepsie, NY: Daniel Friedman; 2001. Available
from URL: http://www.inspect-ny.com/structure/
foundation.htm.
7. Association of Bay Area Governments. Foundations:
section 5. Oakland, CA: Association of Bay Area
Governments; 1998. Available from URL: http://www.
abag.ca.gov/bayarea/eqmaps/ fixit/ch5.
8. Crawford CB. CBD-148: foundation measurements.
Ottawa, Ontario, Canada: National Research Council;
1972. Available from URL: http://irc.nrc-cnrc.gc.ca/cbd/
cbd148e.html.
9. Hamilton JJ. CBD-184: foundations on swelling or
shrinking subsoils. Ottawa, Ontario, Canada: National
Research Council; 1977. Available from URL: http://irc.
nrc-cnrc.gc.ca/pubs/cbd/cbd184_e.html.
P.
The front porch of the home is constructed of pressuretreated, insect-resistant lumber. The use of such lumber
should be carefully evaluated with respect to what
chemicals have been used and the potential for human
exposure to the treated wood. Composite wood products
and plastic decking materials, collectively called Trex,
are available as an alternative to pressure-treated wood.
A proper hand railing and balusters will be installed.
10. US Department of Housing and Urban Development.
Basements and crawl spaces. Washington, DC: US
Department of Housing and Urban Development; 2000.
Available from URL: http://www.hud.gov/offices/hsg/sfh/
ref/sfhp1-25.cfm.
11. Bateman BW. Light-gauge steel verses conventional wood
framing in residential construction. J Construction Educ
1997;2(2):99–108.
12. National Association of Home Builders Research Center.
Integrated steel/wood combination framing. Upper
Marlboro, MD: National Association of Home Builders;
no date. Available from URL: http://www.toolbase.org/
tertiaryT.asp?DocumentID=4249&CategoryID=1142.
13. Steel Wood Studs. Why use steel wood studs? Reno, NV:
Steel Wood Studs; 2001.
14. Canadian Mortgage and Housing Corporation.
Understanding window terminology. Ottawa, Ontario,
Canada: Canadian Mortgage and Housing Corporation;
no date. Available from URL: http://www.cmhc-schl.gc.
ca/en/burema/gesein/abhose/abhose_061.cfm.
15. US Consumer Product Safety Commission. Safety
commission publishes Final Rules for automatic garage
door openers. Washington, DC: US Consumer Product
Safety Commission; 1992. Available from URL: http://
www.cpsc.gov/cpscpub/prerel/prhtml93/93024.html.
Additional Sources of Information
Carmody J, Christian J, Labs K, editors. Builder’s foundation handbook. Oak Ridge, TN: Oak Ridge National
Laboratory; 1991.
US Department of Housing and Urban Development.
Basements and crawl spaces. Washington, DC: US
Department of Housing and Urban Development; 2000.
Available from URL: http://www.hud.gov/offices/ hsg/
sfh/ref/sfhp1-25.cfm.
Healthy Housing Reference Manual6-22 Chapter 6: Housing Structure
7-1Chapter 7: Environmental BarriersHealthy Housing Reference Manual
“The physician can bury his mistakes, but the architect can
only advise his client to plant vines— so they should go as far
as possible from home to build their first buildings.”
Frank Lloyd Wright
New York Times, October 4, 1953
Introduction
Damaging moisture originates not only from outside a
home; it is created inside the home as well. Moisture is
produced by smoking; breathing; burning candles; washing and drying clothes; and using fireplaces, gas stoves,
furnaces, humidifiers, and air conditioning. Leaks from
plumbing, unvented bathrooms, dishwashers, sinks,
toilets, and garbage disposal units also create moisture
problems because they are not always found before water
damage or mold growth occurs. Figure 7.1 provides an
overview of the sources of moisture and types of air pollutants that can enter a home.
Solving moisture problems is often expensive and timeconsuming. The first step is to do a moisture inventory to
eliminate problems in their order of severity. Problems
that are easiest and least expensive to resolve should be
addressed first. For example, many basement leaks have
been eliminated by making sure sump pumps and downspouts drain away from the house. On the other hand,
moisture seeping though basement or foundation walls
often is very expensive to repair. Eliminating such moisChapter 7: Environmental Barriers
Figure 7.1. Sources of Moisture and Air Pollutants [1]
ture is seldom as simple as coating the interior wall, but
often requires expert consultation and excavating around
the perimeter of the house to install or clean clogged
footing drains. Sealing the outside of the basement walls
and coating the exterior foundation wall with tar or other
waterproofing compounds are often the only solutions to
eliminate moisture.
Moisture condensation occurs in both winter and summer. The following factors increase the probability of
condensation:
• Homes that are ineffectively insulated and are not
sealed against air infiltration in cold climates can result
in major moisture problems.
• Cool interior surfaces such as pipes, windows, tile
floors, and metal appliances; air conditioner coils with
poor outside drainage; masonry or concrete surfaces;
toilet tanks; and, in the winter, outside walls and
ceilings can result in moisture buildup from
condensation. If the temperature of an interior surface
is low enough to reach the dew point, moisture in the
air will condense on it and enhance the growth of
mold.
• Dehumidifiers used in regions where outside humidity
levels are normally 80% or higher have a moisturecollecting tank that should be cleaned and disinfected
regularly to prevent the growth of mold and bacteria.
Healthy Housing Reference Manual7-2 Chapter 7: Environmental Barriers
It is best if dehumidifiers have a drain line
continuously discharging directly to the outside or into
a properly plumbed trap. This is also true in climates
where air conditioning units are used on a full-time or
seasonal basis. Their cooling pans provide an excellent
environment for the growth of allergenic or pathogenic
organisms.
• Moisture removed from clothing by clothes driers ends
up in the dryer vent if it is clogged by lint or
improperly configured. Moisture buildup in this vent
can result in mold growth and, if leakage occurs,
damage to the structure of the home. The vent over
the cooking area of the kitchen also should be checked
routinely for moisture or grease buildup.
Roof
The control of moisture in a home is of paramount
importance. It is no surprise that moisture control begins
with the design and integrity of the roof. Many types of
surfacing materials are used for roofs-stone, composition
asphalt, plastic, or metal, for example. Some have relatively short lives and some, such as slate and tile, have
extraordinarily long lives. As in nearly all construction
materials, tradeoffs must be made in terms of cost, thermal efficiency, and longevity. However, all roofs have two
things in common: the need to shed moisture and protect
the interior from the environment.
When evaluating the roof of a home, the first thing to
observe is the roofline against the sky to see if the roof ’s
ridge board is straight and level. If the roofline is not
straight, it could mean that serious deterioration has
taken place in the structure of the home as a result of
1. Is the roofline of the house straight?
2. Are there ripples or waves in the roof?
3. What is the condition of the gutters and downspouts?
4. What is the condition of the boards the gutters are attached to?
5. Does the flashing appear to be separated or damaged?
6. s there any apparent damage in the attic or can sunlight be seen through the roof?
7. Is there mold or discoloration on the rafters or roof sheathing?
8. Is there evidence of corrosion between the gutter and downspouts and any metal roofing or aluminum siding?
9. Do the downspouts route the water away from the base or foundation of the home?
10. Are the gutters covered or free of leaves? Are they sagging or separating from the fascia?
11. Does the gutter provide a mosquito-breeding area by holding water?
Roof Inspection
improper construction, weight buildup, a deteriorated or
broken ridge beam, or rotting rafters. Whatever the cause,
the focus of an inspection must be to locate the extent of
the damage.
The next area to inspect is around the flashing on the roof.
Flashing is used around any structure that penetrates the
surface of a roof or where the roofline takes another direction. These areas include chimneys, gas vents, attic vents,
dormers, and raised and lowered roof surfaces. One of the
best ways to locate a leak around flashing is to go into the
attic and look carefully. Leaks often are discovered when it
rains; but if it is not raining, the underside of the roof can
be examined with the attic lights off for pinpoints of
daylight.
Roofing material should lay relatively flat and should not
wave or ripple. The roof should be checked for missing or
damaged shingles, areas where flashing should be installed,
elevation changes in roof surfaces, and evidence of decomposing or displaced surfaces around the edge of the roof
[1–3].
Insulation
A house must be able to breathe; therefore, air must not be
trapped inside, but must be allowed to exit the home with
its moisture. Moisture buildup in the home will lead to
both mold and bacteria growth. Figure 7.2 demonstrates
insulation blown into an attic, to a depth of approximately
12 inches (Figure 7.3). Figure 7.4 shows the area extending from a house under the roof, known as the soffit. The
soffit is perforated so that air can flow into the attic and
up through the ridge vents to ventilate the attic.
7-3Chapter 7: Environmental BarriersHealthy Housing Reference Manual
If insulation is too thick or installed improperly, it restricts
proper air turnover in the attic and moisture or extreme
temperatures could result in mold or bacteria growth, as
well as delamination of the plywood and particleboards
and premature aging of the roof ’s subsurface and shingles.
Care also must be taken in cold climates to ensure that
the insulation has a vapor barrier and that it is installed
face down. When insulation is placed in the walls of a
home, a thin plastic vapor barrier should be placed over
the insulation facing the inside of the home. The purpose
of this vapor barrier is to keep moisture produced inside
the house from compromising the insulation. If the barrier is not installed, warm, moist air will move through
the drywall and into the insulated wall cavity. When the
air cools, moisture will condense on the fibers of the insulation making it wet; and, if it is cellulose insulation, it
will absorb and hold the moisture. Wetness reduces the
effectiveness of the insulation and provides a favorable
environment for the growth of bacteria and mold [4,5].
Siding
Good siding should be attractive, durable, insect- and vermin-resistant, waterproof, and capable of holding a
weather-resistant coating. Fire-resistant siding and roofing
are important in many areas where wildfires are common
and are required by many local building codes.
All exterior surfaces will eventually deteriorate, regardless
of manufacturer warranties or claims. Leaks in the home
from the outside occur in many predictable locations. The
exterior siding or brick should be checked for cracks or
gaps in protective surfaces. Where plumbing, air vents,
electrical outlets, or communication lines extend through
an exterior wall, they should be carefully checked to
Figure 7.2. Blown Attic Insultation
Figure 7.3. Depth of Attic Insulation
Figure 7.4. Attic ventilation
ensure an airtight seal around those openings. The exterior surface of the home has doors, windows, and other
openings. These openings should be caulked routinely,
and the drainage gutters along the top should be checked
to ensure that they drain properly.
Exterior surface materials include stucco, vinyl, asbestos
shingles, brick, metal (aluminum), fiber cement, exterior
plywood, hardwood, painted or coated wood, glass, and
tile, some of which are discussed in this chapter [6,7].
Healthy Housing Reference Manual7-4 Chapter 7: Environmental Barriers
Stucco
Synthetic stucco (exterior insulation and finish system;
EIFS) is a multilayered exterior finish that has been used
in Europe since shortly after World War II, when contractors found it to be a good repair choice for buildings damaged during the war. North American builders began using
EIFS in the 1980s, first in commercial buildings, then as
an exterior finish to wood frame houses.
EIFS has three layers:
• Inner layer— foam insulation board secured to the
exterior wall surface, often with adhesive;
• Middle layer— a polymer and cement base coat
applied to the top of the insulation, then reinforced
with glass fiber mesh; and
• Exterior layer— a textured finish coat.
EIFS layers bond to form a covering that does not breathe.
If moisture seeps in, it can become trapped behind the layers. With no place to go, constant exposure to moisture
can lead to rot in wood and other vulnerable materials
within the home. Ripples in the stucco could be a sign of
a problem. On the surface it may look like nothing is
wrong, but beneath the surface, the stucco may have
cracked from settling of the house. With a properly
installed moisture barrier, no moisture should be able to
seep behind the EIFS, including moisture originating
inside the home. Drains in the foundation can be designed
to enable moisture that does seep in to escape.
Other signs of problems are mold or mildew on the interior or exterior of the home, swollen wood around door
and window frames, blistered or peeling paint; and
cracked EIFS or cracked sealant.
Vinyl
Standard vinyl siding is made from thin, flexible sheets of
plastic about 2 mm thick, precolored and bent into shape
during manufacturing. The sheets interlock as they are
placed above one another. Because temperature and sunlight cause vinyl to expand and contract, it fits into deep
channels at the corners and around windows and doors.
The channels are deep enough that as the siding contracts,
it remains within the channel.
Siding composed of either vinyl or aluminum will expand
and contract in response to temperature change. This
requires careful attention to the manufacturer’s specifications during application. Cutting the siding too short
causes exposed surfaces when the siding contracts, resulting in moisture damage and eventual leakage. Even small
cracks exposing the undersurface can create major damage.
Fiber Cement
Fiber cement siding is engineered composite-material
products that are extremely stable and durable. Fiber
cement siding is made from a combination of cellulose
fiber material, cement and silica sand, water, and other
additives. Fiber cement siding is fire resistant and useful
in high-moisture areas.
The fiber cement mixture is formed into siding or individual boards, then dried and cured using superheated steam
under pressure. The drying and curing process assures that
the fiber cement siding has very low moisture content,
which makes the product is stable— no warping or excessive movement— and its surface good for painting.
Weight is a minor concern with fiber cement products:
they weigh about 1½ times what comparably sized composite wood products do. Other concerns relate to cutting
fiber cement: cutting produces a fine dust with microscopic silica fibers, so personal protective equipment (respirator and goggles) are necessary. In addition, special
tools are needed for cutting.
Brick
Brick homes may seem on the surface to be nearly maintenance free. This is true in some cases, but, like all surfaces, brick also degrades. Although this degradation takes
longer in brick than in other materials, repairing brick is
complex and quite expensive. There are two basic types of
brick homes. One is brick veneer, which is a thin brick set
to the outside of a wooden stud wall. The brick is not
actually the supporting wall. Brick veneer typically has the
same pattern of bricks around the doors and windows; a
true brick wall will have brick arches or heavy steel plates
above the doors and other openings of the building. Some
brick walls have wooden studs behind the brick to provide an area for insulation, plumbing, vents, and wiring.
It is important that weep holes and flashing be installed
in brick homes to control moisture.
Improperly constructed building footers can result in
major damage to the exterior brick surface of a home by
allowing moisture, insects, and vermin to enter. A crack,
such as the one in Figure 7.5, is an example of such a failure. This type of damage will require much more than
just a mortar patch. Buildings constructed of concrete
block also experience footer failure.
The damage is reason to not skimp
when installing and inspecting the
footing and reinforces the need for
appropriate concrete mix, rebar, and
footing drains.
Figure 7.5. Brick
Structural Defect
7-5Chapter 7: Environmental BarriersHealthy Housing Reference Manual
rent, it will gradually dissolve into ions in the electrolyte
and, at the same time, produce electrons, which the least
active (cathode) will receive through the metallic connection with the anode. The result is that the cathode will be
negatively polarized and hence be protected against
corrosion.
Thus, less noble metals are more susceptible to corrosion.
An example of protecting an appliance such as an ironbodied water heater would be to ensure that piping connections are of similar material when possible and follow
the manufacturer’s good practice and instructions on
using dielectric (not conductors of electricity) unions [8].
Figure 7.6 shows examples of electrochemical kinetics in
pipes that were connected to dissimilar metals.
Vinyl has some environmental and health concerns, as do
most exterior treatments. Vinyl chloride monomer, of
which polyvinyl chloride siding is made, is a strong carcinogen and, when heated, releases toxic gases and vapors.
Under normal conditions, significant exposures to vinyl
chloride monomer are unlikely.
Asbestos
Older homes were often sided with composites containing asbestos. This type of siding was very popular in the
early 1940s. It was heavily used through the 1950s and
decreasingly used up until the early 1960s. The siding is
typically white, although it may be painted. It is often
about ¼-inch thick and very brittle and was sold in sections of about 12×18 inches. The composite is quite
heavy and very slatelike in difficulty of application. As it
ages, it becomes even more brittle, and the surface erodes
and becomes powdery. This siding, when removed, must
be disposed of in accordance with local, state, and federal
laws regulating the disposal of asbestos materials. The
workers and the site must be carefully managed and protected from contamination. The composite had several
virtues as siding. It was quite resistant to fire, was not
attractive to insects or vermin, provided very good insulation, and did not grow mold readily. Because of its very
brittle nature, it could be damaged by children playing
and, as a result, often was covered later with aluminum
siding.
Metal
If metal siding is used, the mounting fasteners (nails or
screws) must be compatible with the metal composition
of the siding, or the siding or fasteners will corrode. This
corrosion is due to galvanic response.
Galvanic response (corrosion) can produce devastating
results that often are only noticed when it is too late. It
should always be considered in inspections and is preventable in nearly all cases.
When two dissimilar metals, such as aluminum and steel,
are coupled and subjected to a corrosive environment
(such as air, water, salt spray, or cleaning solutions), the
more active metal (aluminum) becomes an anode and
corrodes through exfoliation or pitting. This can happen
with plumbing, roofing, siding, gutters, metal venting,
and heating and air conditioning systems.
When two metals are electrically connected to each other
in a conductive environment, electrons flow from the
more active metal to the less active because of the difference in the electrical potential, the so-called “driving
force.” When the most active metal (anode) supplies curFigure 7.6. Corrosion in Piping Resulting From Galvanic Response
Use like metals when possible
Use metals with similar electronegativity levels
Use dielectric unions for plumbing
Use anodes that are inexpensive to replace
Remember: Use metals with less susceptibility to protect
metals that are more susceptible to corrosion.
Metal Corrosion Prevention
References
1. Lawrence Berkeley National Laboratory. Cool roofing
materials database. Berkeley, CA: Lawrence Berkeley
National Laboratory, Environmental Energy Technologies
Division; 2000. Available from URL: http://eetd.lbl.gov/
coolroof/.
2. California Energy Commission. Roofing. Sacramento:
California Energy Commission; no date. Available from
URL: http://www.consumerenergycenter.org/
homeandwork/homes/construction/roofing.html.
Healthy Housing Reference Manual7-6 Chapter 7: Environmental Barriers
3. Cazayoux EJ, Bilello RA. Roof materials. Baton Rouge,
LA: Louisiana State University; no date. Available from
URL: http://www.leeric.lsu.edu/ bgbb/7/ecep/carpntry/i/i.
htm.
4. Department of Energy. Insulation fact sheet. Washington,
DC: Department of Energy; 2002. Available from URL:
http://www.ornl.gov/sci/roofs+walls/insulation/ins_01.htm.
5. The Old House Web. Insulation: stories and more from the
Old House Web. Gardiner, ME: The Old House Web; no
date. Available from URL: http://www.oldhouseweb.com/
stories/HowTo/HVAC_and_Insulation/Insulation/.
6. The Old House Web. Siding: stories and more from the
Old House Web. Gardiner, ME: The Old House Web; no
date. Available from URL: http://www.oldhouseweb.com/
stories/How-To/Siding/.
7. Vandervort D. House siding and architectural details.
Glendale, CA: Hometips.com; no date. Available from
URL: http://www.hometips.com/home_improvement/
siding.html.
8. University of Wisconsin-Stevens Point. Corrosion, lead,
copper: in-home water supplies— are you at risk? Stevens
Point, WI: University of Wisconsin-Stevens Point; no date.
Available from URL: https://www.uwsp.edu/cnr/etf/corros.
htm.
8-1Chapter 8: Rural Water Supplies and Water-quality IssuesHealthy Housing Reference Manual
“We never know the worth of water till the well is dry.”
Thomas Fuller
Gnomologia, 1732
Introduction
One of the primary differences between rural and urban
housing is that much infrastructure that is often taken for
granted by the urban resident does not exist in the rural
environment. Examples range from fire and police protection to drinking water and sewage disposal. This chapter
is intended to provide basic knowledge about the sources
of drinking water typically used for homes in the rural
environment. It is estimated that at least 15% of the population of the United States is not served by approved
public water systems. Instead, they use individual wells
and very small drinking water systems not covered by the
Safe Water Drinking Act (SDWA); these wells and systems are often untested and contaminated [1]. Many of
these wells are dug rather than drilled. Such shallow
sources frequently are contaminated with both chemicals
and bacteria. Figure 8.1 shows the change in water supply
source in the United States from 1970 to 1990.
According to the 2003 American Housing Survey, of the
105,843,000 homes in the United States, water is provided to 92,324,000 (87.2%) by a public or private business; 13,097,000 (12.4%) have a well (11,276,000
drilled, 919,000 dug, and 902,000 not reported) [3].
Water Sources
The primary sources of drinking water are groundwater
and surface water. In addition, precipitation (rain and
snow) can be collected and contained. The initial quality
Chapter 8: Rural Water Supplies and Water-quality Issues
Figure 8.1. U.S. Water Supply by Source [2]
of the water depends on the source. Surface water (lakes,
reservoirs, streams, and rivers), the drinking water source
for approximately 50% of our population, is generally of
poor quality and requires extensive treatment.
Groundwater, the source for the other approximately 50%
of our population, is of better quality. However, it still
may be contaminated by agricultural runoff or surface
and subsurface disposal of liquid waste, including leachate
from solid waste landfills. Other sources, such as spring
water and rain water, are of varying levels of quality, but
each can be developed and treated to render it potable.
Most water systems consist of a water source (such as a
well, spring, or lake), some type of tank for storage, and a
system of pipes for distribution. Means to treat the water
to remove harmful bacteria or chemicals may also be
required. The system can be as simple as a well, a pump,
and a pressure tank to serve a single home. It may be a
complex system, with elaborate treatment processes, multiple storage tanks, and a large distribution system serving
thousands of homes. Regardless of system size, the basic
principles to assure the safety and potability of water are
common to all systems. Large-scale water supply systems
tend to rely on surface water resources, and smaller water
systems tend to use groundwater.
Groundwater is pumped from wells drilled into aquifers.
Aquifers are geologic formations where water pools, often
deep in the ground. Some aquifers are actually higher
than the surrounding ground surface, which can result in
flowing springs or artesian wells. Artesian wells are often
drilled; once the aquifer is penetrated, the water flows
onto the surface of the ground because of the hydrologic
pressure from the aquifer.
Healthy Housing Reference Manual8-2 Chapter 8: Rural Water Supplies and Water-quality Issues
SDWA defines a public water system as one that provides
piped water to at least 25 persons or 15 service connections for at least 60 days per year. Such systems may be
owned by homeowner associations, investor-owned water
companies, local governments, and others. Water not
from a public water supply, and which serves one or only
a few homes, is called a private supply. Private water supplies are, for the most part, unregulated. Community
water systems are public systems that serve people yearround in their homes. The U.S. Environmental
Protection Agency (EPA) also regulates other kinds of
public water systems-such as those at schools, factories,
campgrounds, or restaurants-that have their own water
supply.
The quantity of water in an aquifer and the water produced by a well depend on the nature of the rock, sand,
or soil in the aquifer where the well withdraws water.
Drinking water wells may be shallow (50 feet or less) or
deep (more than 1,000 feet).
On average, our society uses almost 100 gallons of drinking water per person per day. Traditionally, water use rates
are described in units of gallons per capita per day (gallons used by one person in 1 day). Of the drinking water
supplied by public water systems, only a small portion is
actually used for drinking. Residential water consumers
use most drinking water for other purposes, such as toilet
flushing, bathing, cooking, cleaning, and lawn watering.
The amount of water we use in our homes varies during
the day:
• Lowest rate of use— 11:30 pm to 5:00 am,
• Sharp rise/high use— 5:00 am to noon (peak hourly
use from 7:00 am to 8:00 am),
• Moderate use— noon to 5:00 pm (lull around 3:00
pm), and
• Increasing evening use— 5:00 pm to 11:00 pm
(second minor peak, 6:00 pm to 8:00 pm).
Source Location
The location of any source of water under consideration
as a potable supply, whether individual or community,
should be carefully evaluated for potential sources of contamination. As a general practice, the maximum distance
that economics, land ownership, geology, and topography
will allow should separate a water source from potential
contamination sources. Table 8.1 details some of the
sources of contamination and gives minimum distances
recommended by EPA to separate pollution sources from
the water source.
Water withdrawn directly from rivers, lakes, or reservoirs
cannot be assumed to be clean enough for human consumption unless it receives treatment. Water pumped
from underground aquifers will require some level of
treatment. Believing surface water or soil-filtered water
has purified itself is dangerous and unjustified. Clear
water is not necessarily safe water. To assess the level of
treatment a water source requires, follow these steps:
• Determine the quality needed for the intended
purpose (drinking water quality needs to be evaluated
under the SDWA).
• For wells and springs, test the water for bacteriologic
quality. This should be done with several samples
taken over a period of time to establish a history on
the source. With few exceptions, surface water and
groundwater sources are always presumed to be
bacteriologically unsafe and, as a minimum, must be
disinfected.
• Analyze for chemical quality, including both legal
(primary drinking water) standards and aesthetic
(secondary) standards.
• Determine the economical and technical restraints
(e.g., cost of equipment, operation and maintenance
costs, cost of alternative sources, availability of power).
• Treat if necessary and feasible.
Pollution Source Minimum Surface Distance From Well
Septic tank 50 feet
Livestock yard silos
Septic leach fields
50 feet
Petroleum tanks
Liquid-tight manure storage
Pesticide and fertilizer storage and handling
100 feet
Manure stacks 250 feet
Table 8.1. Recommended Minimum Distance Between Well and Pollution Sources (Horizontal Distance) [1]
8-3Chapter 8: Rural Water Supplies and Water-quality IssuesHealthy Housing Reference Manual
Well Construction
Many smaller communities obtain drinking water solely
from underground aquifers. In addition, according to the
last census with data on water supply systems, 15% of
people in the United States are on individual water supply systems. In some sections of the country, there may
be a choice of individual water supply sources that will
supply water throughout the year. Some areas of the
country may be limited to one source. The various
sources of water include drilled wells, driven wells, jetted
wells, dug wells, bored wells, springs, and cisterns. Table
8.2 provides a more detailed description of some of these
wells.
Regardless of the choice for a water supply source, special
safety precautions must be taken to assure the potability
of the water. Drainage should be away from a well. The
casings of the well should be sealed with grout or some
other mastic material to ensure that surface water does
not seep along the well casing to the water source. In
Figure 8.2, the concrete grout has been reinforced with
steel and a drain away from the casing has been provided
to assist in protecting this water source. Additionally,
research suggests that a minimum of 10 feet of soil is
essential to filter unwanted biologic organisms from the
water source.
However, if the area of well construction has any sources
of chemical contamination nearby, the local public health
authority should be contacted. In areas with karst topography (areas characterized by a limestone landscape with
caves, fissures, and underground streams), wells of any
type are a health risk because of the long distances that
both chemical and biologic contaminants can travel.
When determining where a water well is to be located,
several factors should be considered:
• the groundwater aquifer to be developed,
• depth of the water-bearing formations,
Figure 8.2. Cross Section of a Driven Well
• the type of rock formations that will be encountered,
• freedom from flooding, and
• relation to existing or potential sources of
contamination.
The overriding concern is to protect any kind of well
from pollution, primarily bacterial contamination.
Groundwater found in sand, clay, and gravel formations
is more likely to be safer than groundwater extracted
from limestone and other fractured rock formations.
Whatever the strata, wells should be protected from
• surface water entering directly into the top of the well,
• groundwater entering below ground level without
filtering through at least 10 feet of earth, and
• surface water entering the space between the well
casing and surrounding soil.
Also, a well should be located in such a way that it is
accessible for maintenance, inspection, and pump or pipe
replacement when necessary. Driven wells (Figure 8.2) are
typically installed in sand or soil and do not penetrate
base rock. They are, as a result, hammered into the
Type of Well Depth, in Feet Diameter Suitable Geologic Formations
Dug 0–50 typically
less than 25
3 to 20 feet Suitable in clay, silt, sand, gravel, and soft fractured limestone
Bored 0–100 2 to 30 inches Clay, silt, sand, gravel, boulders less than well diameter, soft
sandstone, and fractured limestone
Driven 0–50 1.25 to 2
inches
Clay, sand, silt, fine gravel, and thin layers of sandstone
Drilled (rotary type) 0–1,000 4 to 24 inches Same as above with percussion type drilling
Table 8.2. Types of Wells for Accessing Groundwater, Well Depths, and Diameters
Healthy Housing Reference Manual8-4 Chapter 8: Rural Water Supplies and Water-quality Issues
and another pulling the dirt from the hole with a rope,
pulley, and bucket. Of course, this required a hole of
rather large circumference, with the size increasing the
potential for leakage from the surface. The dug well also
was traditionally quite shallow, often less than 25 feet,
which often resulted in the water source being contaminated by surface water as it ran through cracks and crevices in the ground to the aquifer. Dug wells provide
potable water only if they are properly located and the
water source is free of biologic and chemical contamination. The general rule is, the deeper the well, the more
likely the aquifer is to be free of contaminants, as long as
surface water does not leak into the well without sufficient soil filtration.
Two basic processes are used to remediate dug wells. One
is to dig around the well to a depth of 10 feet and install
a solid slab with a hole in it to accommodate a well casing and an appropriate seal (Figures 8.4 and 8.5). The
dirt is then backfilled over the slab to the surface, and the
casing is equipped with a vent and second seal, similar to
a drilled well, as shown in Figure 8.6. This results in a
considerable reduction in the area of the casing that needs
ground and are quite shallow, resulting in frequent contamination by both chemical and bacterial sources.
Sanitary Design and Construction
Whenever a water-bearing formation is penetrated (as in
well construction), a direct route of possible water contamination exists unless satisfactory precautions are taken.
Wells should be provided with casing or pipe to an adequate depth to prevent caving and to permit sealing of
the earth formation to the casing with watertight cement
grout or bentonite clay, from a point just below the surface to as deep as necessary to prevent entry of contaminated water.
Once construction of the well is completed, the top of
the well casing should be covered with a sanitary seal, an
approved well cap, or a pump mounting that completely
covers the well opening (Figure 8.3). If pumping at the
design rate causes drawdown in the well, a vent through a
tapped opening should be provided. The upper end of
the vent pipe should be turned downward and suitably
screened to prevent the entry of insects and foreign
matter.
Figure 8.4. Converted Dug Well [1]
Figure 8.3. Well Seal
Pump Selection
A variety of pump types and sizes exist to meet the needs
of individual or community water systems. Some of the
factors to be considered in selecting a pump for a specific
application are well depth, system design pressure,
demand rate in gallons per minute, availability of power,
and economics.
Dug and Drilled Wells
Dug wells (Figures 8.4 and 8.5) were one of the most
common types of wells for individual water supply in the
United States before the 1950s. They were often constructed with one person digging the hole with a shovel
8-5Chapter 8: Rural Water Supplies and Water-quality IssuesHealthy Housing Reference Manual
to be protected. Experience has shown that the disturbed
dirt used for backfilling over the buried slab will continue
to release bacteria into the well for a short time after
modification. Most experts in well modification suggest
installing a chlorination system on all dug wells to disinfect the water because of their shallow depth and possible
biologic impurity during changing drainage and weather
conditions above ground. Figure 8.7 shows a dug well
near the front porch of a house and within 5 feet of a
drainage ditch and 6 feet of a rural road. This well is
likely to be contaminated with the pesticide used to termite-proof the home and from whatever runs off the
nearby road and drainage ditch. The well shown is about
15 feet deep. The brick structure around the well holds
the centrifugal pump and a heater to keep the water from
freezing. Although dangerous to drink from, this well is
typical of dug wells used in rural areas of the United
States for drinking water.
Figure 8.5. Recapped and Sealed Dug Well [1]
Figure 8.6. Drilled Well [4]
Figure 8.7. Typical Dug Well
Samples should not be taken from such wells because
they instill a false sense of security if they are negative for
both chemicals and biologic organisms. The quality of
the water in such wells can change in just a few hours
through infiltration of drainage water. Figure 8.8 shows
the septic tank discharge in the drainage ditch 5 feet
upstream of the dug well in Figure 8.7. This potential
combination of drinking water and waste disposal presents an extreme risk to the people serviced by the dug
well. Sampling is not the answer; the water source should
be changed under the supervision of qualified environmental health professionals.
Healthy Housing Reference Manual8-6 Chapter 8: Rural Water Supplies and Water-quality Issues
Figure 8.9 shows a drilled well. On the left side of the
picture is the corner of the porch of the home. The well
appears not to have a sanitary well seal and is likely open
to the air and will accept contaminants into the casing.
Because the well is so close to the house, the casing is
open, and the land slopes toward the well, it is a major
candidate for contamination and not a safe water source.
Springs
Another source of water for individual water supply is
natural springs. A spring is groundwater that reaches the
surface because of the natural contours of the land.
Springs are common in rolling hillside and mountain
areas. Some provide an ample supply of water, but most
provide water only seasonally. Without proper precautions, the water may be biologically or chemically contaminated and not considered potable.
Figure 8.10. Spring Box [5]
Figure 8.8. Sewage in Drainage Ditch
Figure 8.9. Drilled Well
To obtain satisfactory (potable) water from a spring, it is
necessary to
• find the source,
• properly develop the spring,
• eliminate surface water outcroppings above the spring
to its source,
• prevent animals from accessing the spring area, and
• provide continuous chlorination.
Figure 8.10 illustrates a properly developed spring. Note
that the line supplying the water is well underground, the
spring box is watertight, and surface water runoff is
diverted away from the area. Also be aware that the water
quality of a spring can change rapidly.
Cisterns
A cistern is a watertight, traditionally underground reservoir that is filled with rainwater draining from the roof of
a building. Cisterns will not provide an ample supply of
water for any extended period of time, unless the amount
of water used is severely restricted. Because the water is
coming off the roof, a pipe is generally installed to allow
redirection of the first few minutes of rainwater until the
water flows clear. Disinfection is, nevertheless, of utmost
importance. Diverting the first flow of water does not
assure safe, non-polluted water because chemicals and
biologic waste from birds and other animals can migrate
from catchment surfaces and from windblown sources. In
addition, rainwater has a low pH, which can corrode
plumbing pipes and fixtures if not treated.
8-7Chapter 8: Rural Water Supplies and Water-quality IssuesHealthy Housing Reference Manual
Disinfection of Water Supplies
Water supplies can be disinfected by a variety of methods
including chlorination, ozonation, ultraviolet radiation,
heat, and iodination. The advantages and disadvantages
of each method are noted in Table 8.3.
The understanding of certain terms (blue box, next page)
is necessary in talking about chlorination.
Table 8.4 is a chlorination guide for specific water
conditions.
Chlorine is the most commonly used water disinfectant.
It is available in liquid, powder, gas, and tablet form.
Chlorine gas is often used for municipal water disinfection, but can be hazardous if mishandled. Recommended
liquid, powder, and tablet forms of chlorine include the
following:
• Liquid— Chlorine laundry bleach (about 5%
chlorine). Swimming pool disinfectant or concentrated
chlorine bleach (12%–17% chlorine).
• Powder— Chlorinated lime (25% chlorine), dairy
sanitizer (30% chlorine), and high-test calcium
hypochlorite (65%–75% chlorine).
• Tablets— High-test calcium hypochlorite (65%–75%
chlorine).
• Gas— Gas chlorine is an economical and convenient
way to use large amounts of chlorine. It is stored in
steel cylinders ranging in size from 100 to 2,000
pounds. The packager fills these cylinders with liquid
chlorine to approximately 85% of their total volume;
the remaining 15% is occupied by chlorine gas. These
ratios are required to prevent tank rupture at high
temperatures. It is important that direct sunlight never
reaches gas cylinders. It is also important that the user
of chlorine knows the maximum withdrawal rate of
gas per day per cylinder. For example, the maximum
withdrawal rate from a 150-pound cylinder is
approximately 40 pounds per day at room temperature
discharging to atmospheric pressure.
Disinfection Method Advantages Disadvantages
Boiling Readily accessible
Well suited for emergencies
Removes volatile organic compounds from
water
Effective even on Giardia and Cryptosporidium
Requires a great deal of heat
Takes time to boil and cool
Water tastes stale
Typically limited capacity
Chlorine Provides residual treatment
Residual easy to test and measure
Readily available; reasonable cost
Low electrical requirement
Useful for multiple water problems
Can treat large volumes of water
Requires contact time of 30 minutes
Turbidity reduces effectiveness
Gives water a chlorine taste
May form disinfection by-products
Does not kill Giardia or Cryptosporidium
Requires careful handling and storage
Ultraviolet light Does not change taste of water
Leaves no discernable odor
Kills bacteria almost immediately
Compact and easy to use
High electrical requirement
Provides no residual treatment
Requires pretreatment if turbid
Requires new lamp annually
Iodine Does not require electricity
Requires little maintenance
Provides residual treatment
Residual easy to measure
Health side effects undetermined
Affected by water temperature
Gives water an iodine taste
Ozone Is a more powerful disinfectant than chlorine
Does not change taste of water
Leaves no discernable odor
Ozone gas is unstable and must be generated at
point of use
Table 8.3. Disinfection Methods
Healthy Housing Reference Manual8-8 Chapter 8: Rural Water Supplies and Water-quality Issues
Chlorination Treatment for Typical Dosage Rates
Algae 3 to 5 ppm
Bacteria 3 to 5 ppm
Biologic oxygen demand reduction 10 parts per million
Color (removal) Dosage depends on type and extent of color removal desired; may vary
from 1 to 500 ppm dosage rate
Cyanide
Reduction to cyanate 2 times cyanide content
Complete destruction 8.5 times cyanide content
Hydrogen sulfide
Taste and odor control 2 times hydrogen sulfide content
Destruction 8.4 times hydrogen sulfide content
Iron bacteria 1 to 10 ppm, varying with amount of bacteria to control
Iron precipitation 64 times iron content
Manganese precipitation 1 to 3 times manganese content
Odor 1 to 3 ppm
Taste 1 to 3 ppm
ppm: parts per million
Table 8.4. Chlorination Guide for Specific Water Conditions
Breakpoint chlorination— A process sometimes used to ensure the presence of free chlorine in public water supplies by adding enough chlorine to the water to satisfy the chlorine demand and to react with all dissolved ammonia that might be present. The concentrations of chlorine needed to treat a variety of water conditions are listed in Table 8.4.
Chlorine concentration— The concentration (amount) of chlorine in a volume of water is measured in parts per million
(ppm). In 1 million gallons of water, a chlorine concentration of 1 ppm would require 8.34 pounds of 100% chlorine.
Contact time— The time, after chlorine addition and before use, given for disinfection to occur. For groundwater systems,
contact time is minimal. However, in surface water systems, a contact time of 20 to 30 minutes is common.
Dosage— The total amount of chlorine added to water. Given in parts per million (ppm) or milligrams per liter (mg/L).
Demand— Chlorine solution used by reacting with particles of organic matter such as slimes or other chemicals and minerals that may be present. The difference between the amount of chlorine applied to water and total available chlorine remaining at the end of a specified contact period.
Parts per million— A weight-to-weight comparison; 1 ppm equals 1 pound per million pounds. Because water weighs 8.34
pounds per gallon, it takes 8.34 pounds of any substance per million gallons to equal 1 ppm. In water chemistry, 1 ppm
equals 1 mg/L.
Residual— The amount of chlorine left after the demand is met; available (free) chlorine. This portion provides a ready reserve for bactericidal action. Both combined and free chlorine make up chlorine residual and are involved in disinfection.
Total available chlorine = free chlorine + combined chlorine.
Definitions of Terms Related to Chlorination
8-9Chapter 8: Rural Water Supplies and Water-quality IssuesHealthy Housing Reference Manual
Chlorine Carrier Solutions
On small systems or individual wells, a high-chlorine carrier solution is mixed in a tank in the pump house and
pumped by the chlorinator into the system. Table 8.5
shows how to make a 200-ppm carrier solution. By using
200 ppm, only small quantities of this carrier have to be
added. Depending on the system, other stock solutions
may be needed to better use existing chemical feed
equipment.
Routine Water Chlorination (Simple)
Most chlorinated public water supplies use routine water
chlorination. Enough chlorine is added to the water to
meet the chlorine demand, plus enough extra to supply
0.2 to 0.5 ppm of free chlorine when checked after 20
minutes.
Simple chlorination may not be enough to kill certain
viruses. Chlorine as a disinfectant increases in
effectiveness as the chlorine residual is increased and as
the contact time is increased.
Chlorine solutions should be mixed and chlorinators
adjusted according to the manufacturer’s instructions.
Chlorine solutions deteriorate gradually when standing.
Fresh solutions must be prepared as necessary to maintain
the required chlorine residual. Chlorine residual should
be tested at least once a week to assure effective
equipment operation and solution strengths.
A dated record should be kept of solution preparation,
type, proportion of chlorine used, and residual-test
results. Sensing devices are available that will automatically shut off the pump and activate a warning bell or
light when the chlorinator needs servicing.
Well Water Shock Chlorination
Shock chlorination is used to control iron and sulfatereducing bacteria and to eliminate fecal coliform bacteria
in a water system. To be effective, shock chlorination
must disinfect the following: the entire well depth, the
formation around the bottom of the well, the pressure
system, water treatment equipment, and the distribution
system. To accomplish this, a large volume of super-chlorinated water is siphoned down the well to displace the
water in the well and some of the water in the formation
around the well. Check specifications on the water treatment equipment to ensure appropriate protection of the
equipment.
With shock chlorination, the entire system-from the
water-bearing formation through the well-bore and the
distribution system-is exposed to water that has a concentration
of chlorine strong enough to kill iron and sulfate-reducing
bacteria. The shock chlorination process is complex and
tedious. Exact procedures and concentrations of chlorine
for effective shock treatment are available [6,7].
Backflow, Back-siphonage, and Other Water
Quality Problems
In addition to contamination at its source, water can
become contaminated with biologic materials and toxic
construction or unsuitable joint materials as it flows
through the water distribution system in the home. Water
flowing backwards (backflow) in the pipes sucks materials
back (back-siphonage) into the water distribution system,
creating equally hazardous conditions. Other water quality problems relate to hardness, dissolved iron and iron
bacteria, acidity, turbidity, color, odor, and taste.
Backflow
Backflow is any unwanted flow of nonpotable water into
a potable water system. The direction of flow is the
reverse of that intended for the system. Backflow may be
caused by numerous factors and conditions. For example,
the reverse pressure gradient may be a result of either a
loss of pressure in the supply main (back-siphonage) or
the flow from a pressurized system through an unprotected cross-connection (back-pressure). A reverse flow in
a distribution main or in a customer’s system can be created by a change of system pressure wherein the pressure
at the supply point becomes lower than the pressure at
the point of use. When this happens, the water at the
point of use will be siphoned back into the system,
potentially polluting or contaminating it. It is also possible that contaminated or polluted water could continue
to backflow into the public distribution system. The
point at which nonpotable water comes in contact with
potable water is called a cross-connection.
Examples of backflow causes include supplemental supplies, such as a standby fire protection tank; fire pumps;
chemical feed pumps that overpower the potable water
system pressure; and sprinkler systems.
Carrier Solution
Amount of Chlorine per
100 Gallons of Water
5% chlorine bleach 3 pints
12%–17% chlorine solution 1 pint
25%–30% chlorine powder 2/3 pound
65%–75% chlorine powder 1/4 pound
Table 8.5. Preparing a 200-ppm Chlorine Solution
Healthy Housing Reference Manual8-10 Chapter 8: Rural Water Supplies and Water-quality Issues
Back-Siphonage
Back-siphonage is a siphon action in an undesirable or
reverse direction. When there is a direct or indirect connection between a potable water supply and water of
questionable quality due to poor plumbing design or
installation, there is always a possibility that the public
water supply may become contaminated. Some examples
of common plumbing defects are
• washbasins, sterilizers, and sinks with submerged inlets
or threaded hose bibs and hose;
• oversized booster pumps that overtax the supply
capability of the main and thus develop negative
pressure;
• submerged inlets and fire pumps (if the fire pumps are
directly connected into the water main, a negative
pressure will develop); and
• a threaded hose bib in a health-care facility (which is
technically a cross-connection).
There are many techniques and devices for preventing
back-flow and back-siphonage. Some examples are
• Vacuum breakers (nonpressure and pressure);
• Back-flow preventers (reduced pressure principle,
double gate-double check valves, swing-connection,
and air gap-double diameter separation);
• Surge tanks (booster pumps for tanks, fire system
make-up tank, and covering potable tanks); and
• Color coding in all buildings where there is any
possibility of connecting two separate systems or
taking water from the wrong source (blue-potable,
yellow-nonpotable, and other-chemical and gases).
An air gap is a physical separation between the incoming
water line and maximum level in a container of at least
twice the diameter of the incoming water line. If an air
gap cannot be installed, then a vacuum breaker should be
installed. Vacuum breakers, unlike air gaps, must be
installed carefully and maintained regularly. Vacuum
breakers are not completely failsafe.
Other Water Quality Problems
Water not only has to be safe to drink; it should also be
aesthetically pleasing. Various water conditions affect
water quality. Table 8.6 describes symptoms, causes, measurements, and how to correct these problems.
Protecting the Groundwater Supply
Follow these tips to help protect the quality of
groundwater supplies:
• Periodically inspect exposed parts of wells for cracked,
corroded, or damaged well casings; broken or missing
well caps; and settling and cracking of surface seals.
• Slope the area around wells to drain surface runoff
away from the well.
• Install a well cap or sanitary seal to prevent
unauthorized use of, or entry into, a well.
• Disinfect wells at least once a year with bleach or
hypochlorite granules, according to the manufacturer’s
directions.
• Have wells tested once a year for coliform bacteria,
nitrates, and other constituents of concern.
• Keep accurate records of any well maintenance, such
as disinfection or sediment removal, that require the
use of chemicals in the well.
• Hire a certified well driller for new well construction,
modification, or abandonment and closure.
• Avoid mixing or using pesticides, fertilizers, herbicides,
degreasers, fuels, and other pollutants near wells.
• Do not dispose of waste in dry or abandoned wells.
• Do not cut off well casings below the land surface.
• Pump and inspect septic systems as often as
recommended by local health departments.
• Never dispose of hazardous materials (e.g., paint, paint
stripper, floor stripper compounds) in a septic system.
References
1. Rhode Island Department of Health and University of
Rhode Island Cooperative Extension Water Quality
Program. Healthy drinking waters for Rhode Islanders.
Kingston, RI: Rhode Island Department of Health and
University of Rhode Island Cooperative Extension Water
Quality Program; 2003. Available from URL: http://www.
uri.edu/ce/wq/has/html/Drinking.pdf.
2. US Census Bureau. Historical census of housing graphs:
water supply. Washington, DC: US Census Bureau; no
date. Available from URL: http://www.census.gov/hhes/
www/housing/census/historic/swgraph.html.
8-11Chapter 8: Rural Water Supplies and Water-quality IssuesHealthy Housing Reference Manual
Table 8.6. Analyzing and Correcting Water Quality Problems (continues on next page)
Symptoms Probable Cause Measurement Corrective Action
Hardness
– Sticky curd forms
when soap is added
to water
– Causes bathtub ring
– Requires more soap
– Glassware appears
streaked, scale forms
in pipes
Calcium and magnesium in
the water, compounded
with biocarbonates,
sulfates, or chlorides.
Hardness test kits, which
measure in grains per gallon
(gpg) or parts per million
(ppm). 1 gpg = 17.1 ppm
50 ppm is soft water; 50 to
100 ppm is moderately hard
water; 100 to 200 ppm is hard
water; 200 to 300 ppm is very
hard; over 300 ppm is
extremely hard
If hardness creates problems,
a sodium zeolite ion exchange
water softener or a reverse
osmosis unit can be used.
Dissolved iron
– Red stains (red
water) on clothes and
plumbing fixtures
– Corrosion of steel
pipes
– Metallic taste
– Clear water just
drawn begins to form
red particles that
settle to the bottom
Iron, from geologic
formations that groundwater passes through.
Water, an excellent solvent,
ionizes iron and holds it in
solution.
Iron is common in soft
water and when water
hardness is above 175 ppm.
Atomic absorption (AA) units
or numerous colormetric test
kits measure iron in ppm.
Any measurement above
0.3 ppm will cause problems.
To treat soft water that
contains no iron but picks it
up in distribution lines, add
calcium to the water with
calcite (limestone) units.
To treat hard water con taining
iron ions, install a sodium
zeolite ion exchange unit.
To treat soft water con taining
iron, carbon dioxide must be
neutralized, followed by a
manganese zeolite unit.
Iron bacteria (red slime
appears in toilet)
Caused by bacteria that act
in the presence of iron.
Check under toilet tank cover
for slippery jelly-like coating.
Kill bacteria by superchlorinating pump and piping
system.
Brownish-black water
– Fixture stains black
– Fabric stains black
– Bitter coffee and tea
Manganese is present
usually along with iron.
Colormetric tests for manganese
(concentrations above
0.05 mg/L cause problems).
Same methods as for iron.
Acidity (corrosion of
copper and steel in
pumps, fixtures, piping
and tanks)
Carbon dioxide forms
carbonic acid. Water may
contain H2SO4, HCl, or
nitric acid, but unlikely.
Colormetric field titrametric
tests for acidity, pH, and
carbon dioxide (pH is
determined at the titration
end point). A pH below 6.5
causes corrosion. Carbon
dioxide should be less than
10 mg/L or less than 5 mg/L if
alkalinity is less than 100 ppm.
Soda ash solution is fed into
the well or suction line of a
pump. May be fed along with
chlorine solution.
Limestone chips (calcite)
neutralize the water by
increasing its alkalinity and
hardness.
Odors and tastes
– Bitter taste Very high mineral content Excess iron, manganese, sulfate Methods mentioned above
– Rotten egg odor Sulfate-reducing bacteria,
hydrogen sulfide
Sulfate levels above 250 mg/L
or any trace of hydrogen sulfide
cause problems
Chlorinator and filter
– Salty taste High chloride levels Problems at levels >250 mg/L Reverse osmosis unit
– Flat, soda taste Bicarbonates Carbonate hardness test Aeration unit
– Salty taste High total dissolved solids
(TDS)
TDS levels above 500 mg/L may
cause problems
Sand filter
– Chlorine odor/taste High levels of di- or
trichloramines in water
Check pH Activated charcoal filter
Healthy Housing Reference Manual8-12 Chapter 8: Rural Water Supplies and Water-quality Issues
3. US Census Bureau. American housing survey.
Washington, DC: US Census Bureau; 2003. Available
from URL: http://www.census.gov/hhes/ www/housing/
ahs/nationaldata.html.
4. National Ground Water Association. Well system material.
Westerville, OH: National Ground Water Association;
2003. Available from URL: http://www.ngwa.org/pdf/
wellsystemmaterials.pdf.
5. US Environmental Protection Agency. Spring
development. Chicago: US Environmental Protection
Agency; 2001.
6. Government of Alberta. Shock chlorination— well
maintenance. Edmonton, Alberta, Canada: Alberta
Agriculture, Food & Rural Development;2001. Available
from URL: http://www1.agric.gov.ab.ca/$department/
deptdocs.nsf/all/wwg411.
7. Boulder GNS Water Well Service and Supply.
Chlorination of water systems. Boulder, CO: Boulder
GNS Water Well Service and Supply; 2002. Available
from URL: http://www.waterwell.cc/CHLORIN.HTM.
8. Iowa State University Diagnosing and solving common
water-quality problems. Ames, IA: Iowa State University;
1994. Available from URL: http://www.abe.iastate.edu/
HTMDOCS/aen152.pdf.
Table 8.6. Analyzing and Correcting Water Quality Problems (continued)
Additional Sources of Information
American Water Works Association. Available from URL:
http://www.awwa.org.
Drexel University: Drinking water outbreaks. Available
from URL: http://water.sesep.drexel.edu/outbreaks/.
US Environmental Protection Agency: Ground water and
drinking water. Available from URL: http://www.epa.gov/
safewater.
Symptoms Probable Cause Measurement Corrective Action
Turbidity (cloudy water) Silt, sediment, large
number of microorganisms
or organic material
Nephelometric turbidity units
(NTUs) using laboratory
spectrophotometers. (Less than
5 NTUs is best, >10 not
acceptable.)
Fine filtering with sand filter
or diatomaceous earth filter.
For ponds, coagula tion and
sedimentation are needed.
Blue stain on porcelain
fixtures
Corrosion of copper pipes
and fixtures due to low pH,
hardness, and alkalinity
Langelier index determines
proper balance of pH, hardness,
and alkalinity.
Methods mentioned above to
adjust pH, hardness, and
alkalinity.
Lead contamination Leaching from lead service
lines, solder, or brass or
lead fittings
15 parts per billion Adjust pH
Filtration
Chemical treatment
9-1Chapter 9: PlumbingHealthy Housing Reference Manual
“The society which scorns excellence in plumbing as a humble
activity and tolerates shoddiness in philosophy because it is an
philosophy: neither its pipes nor its theories will hold water.”
John W. Gardner, Secretary,
Department of Health, Education, and Welfare, 1965
Introduction
Plumbing may be defined as the practice, materials, and
fixtures used in installing, maintaining, and altering piping, fixtures, appliances, and appurtenances in connection
with sanitary or storm drainage facilities, a venting system, and public or private water supply systems.
Plumbing does not include drilling water wells; installing
water softening equipment; or manufacturing or selling
plumbing fixtures, appliances, equipment, or hardware. A
plumbing system consists of three parts: an adequate
potable water supply system; a safe, adequate drainage
system; and ample fixtures and equipment.
The housing inspector’s prime concern while inspecting
plumbing is to ensure the provision of a safe water supply
system, an adequate drainage system, and ample and
proper fixtures and equipment that do not contaminate
water. The inspector must make sure that the system
moves waste safely from the home and protects the occupants from backup of waste and dangerous gases. This
chapter covers the major features of a residential plumbing system and the basic plumbing terms and principles
the inspector must know and understand to identify
housing code violations that involve plumbing. It will
also assist in identifying the more complicated defects
that the inspector should refer to the appropriate agencies. This chapter is not a plumbing code, but should
provide a base of knowledge sufficient to evaluate household systems.
Elements of a Plumbing System
The primary purposes of a plumbing system are
• To bring an adequate and potable supply of hot and
cold water to the inhabitants of a house, and
• To drain all wastewater and sewage discharge from
fixtures into the public sewer or a private disposal
system.
It is, therefore, very important that the housing inspector
be completely familiar with all elements of these systems
so that inadequacies of the structure’s plumbing and other
Chapter 9: Plumbing
Figure 9.1. Typical Home Water System [1]
code violations will be recognized. To aid the inspector in
understanding the plumbing system, a schematic of a
home plumbing system is shown in Figure 9.1.
Water Service
The piping of a house service line should be as short as
possible. Elbows and bends should be kept to a minimum
because they reduce water pressure and, therefore, the
supply of water to fixtures in the house. The house service line also should be protected from freezing. Four feet
of soil is a commonly accepted depth to bury the line to
prevent freezing. This depth varies, however, across the
country from north to south. The local or state plumbing
code should be consulted for recommended depths. The
minimum service line size should be ¾ inch. The minimum water supply pressure should be 40 pounds per
square inch (psi), no cement or concrete joints should be
allowed, no glue joints between different types of plastic
should be allowed, and no female threaded PVC fittings
should be used.
The materials used for a house service may be approved
plastic, copper, cast iron, steel, or wrought iron. The connections used should be compatible with the type of pipe
used. A typical house service installation is pictured in
Figure 9.2. The elements of the service installation are
described below.
Corporation stop— The corporation stop is connected
to the water main. This connection is usually made of
brass and can be connected to the main with a special
tool without shutting off the municipal supply. The valve
Healthy Housing Reference Manual9-2 Chapter 9: Plumbing
incorporated in the corporation stop permits the pressure
to be maintained in the main while the service to the
building is completed.
Curb stop— The curb stop is a similar valve used to isolate the building from the main for repairs, nonpayment,
of water bills or flooded basements. Because the corporation stop is usually under the street and it is necessary to
break the pavement to reach the valve, the curb stop is
used as the isolation valve.
Curb stop box— The curb stop box is an access box to
the curb stop for opening and closing the valve. A longhandled wrench is used to reach the valve.
Air chambers— Pressure-absorbing devices that eliminate water hammer. Air chambers should be installed as close as possible to the valves or faucet and at the end of long runs of pipe.
Air gap (drainage system)— The unobstructed vertical distance through the free atmosphere between the outlet of a water
pipe and the flood level rim of the receptacle into which it is discharging.
Air gap (water distribution system)— The unobstructed vertical distance through the free atmosphere between the lowest
opening from any pipe or faucet supplying water to a tank, plumbing fixture, or other device and the flood level rim of the
receptacle.
Backflow— The flow of water or other liquids, mixtures, or substances into the distributing pipes of a potable water supply
from any source or sources other than the intended source. Back siphonage is one type of backflow.
Back siphonage— The flowing back of used, contaminated, or polluted water from a plumbing fixture or vessel into a potable water supply because of negative pressure in the pipe.
Branch— Any part of the piping system other than the main, riser, or stack.
Branch vent— A vent connecting one or more individual vents with a vent stack.
Building drain— Part of the lowest piping of a drainage system that receives the discharge from soil, waste, or other drainage
pipes inside the walls of the building (house) and conveys it to the building sewer beginning 3 feet outside the building wall.
Cross connection— Any physical connection or arrangement between two otherwise separate piping systems (one of which
contains potable water and the other which contains either water of unknown or questionable safety or steam, gas, or chemical) whereby there may be a flow from one system to the other, the direction of flow depending on the pressure differential
between the two systems. (See Backflow and Back siphonage.)
Disposal field— An area containing a series of one or more trenches lined with coarse aggregate and conveying the effluent
from a septic tank through vitrified clay pipe or perforated, nonmetallic pipe, laid in such a manner that the flow will be distributed with reasonable uniformity into natural soil.
Drain— Any pipe that carries wastewater or waterborne waste in a building (house) drainage system.
Flood level rim— The top edge of a receptacle from which water overflows.
Flushometer valve— A device that discharges a predetermined quantity of water to fixtures for flushing purposes and is
closed by direct water pressures.
Flushometer toilet— a toilet using a flushometer valve that uses pressure from the water supply system rather than the force
of gravity to discharge water into the bowl, designed to use less water than conventional flush toilets.
Flush valve— A device located at the bottom of the tank for flushing toilets and similar fixtures.
Definitions of Terms Related to Home Water Systems
Figure 9.2. House Service Installation [1]
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Meter stop— The meter stop is a valve placed on the
street side of the water meter to isolate it for installation
or maintenance. Many codes require a gate valve on the
house side of the meter to shut off water for plumbing
repairs. The curb and meter stops can be ruined in a
short time if used very frequently.
The water meter is a device used to measure the amount
of water used in the house. It is usually the property of
the water provider and is a very delicate instrument that
should not be abused. In cold climates, the water meter is
often inside the home to keep it from freezing. When the
Grease trap— See Interceptor.
Hot water— Potable water heated to at least 120°F–130°F (49°C–54°C) and used for cooking, cleaning, washing dishes, and
bathing.
Insanitary— Unclean enough to endanger health.
Interceptor— A device to separate and retain deleterious, hazardous, or undesirable matter from normal waste and permit
normal sewage or liquid waste to discharge into the drainage system by gravity.
Main vent— The principal artery of the venting system, to which vent branches may be connected.
Leader— An exterior drainage pipe for conveying storm water from roof or gutter drains to the building storm drain, combined building sewer, or other means of disposal.
Main sewer— See Public sewer.
Pneumatic— Pertaining to devices making use of compressed air as in pressure tanks boosted by pumps.
Potable water— Water having no impurities present in amounts sufficient to cause disease or harmful physiologic effects and
conforming in its bacteriologic and chemical quality to the requirements of the U.S. Environmental Protection Agency’s Safe
Drinking Water Act or meeting the regulations of other agencies having jurisdiction.
P & T (pressure and temperature) relief valve— A safety valve installed on a hot water storage tank to limit temperature
and pressure of the water.
P-trap— A trap with a vertical inlet and a horizontal outlet.
Public sewer— A common sewer directly controlled by public authority.
Relief vent— An auxiliary vent that permits additional circulation of air in or between drainage and systems.
Septic tank— A watertight receptacle that receives the discharge of a building’s sanitary drain system or part thereof and is
designed and constructed to separate solid from liquid, digest organic matter through a period of detention, and allow the
liquids to discharge into the soil outside of the tank through a system of open-joint or perforated piping or through a seepage pit.
Sewerage system— A system comprising all piping, appurtenances, and treatment facilities used for the collection and
disposal of sewage, except plumbing inside and in connection with buildings served, and the building drain.
Soil pipe— The pipe that directs the sewage of a house to the receiving sewer, building drain or building sewer.
Soil stack— The vertical piping that terminates in a roof vent and carries off the vapors of a plumbing system.
Stack vent— An extension of a solid or waste stack above the highest horizontal drain connected to the stack, sometimes
called a waste vent or a soil vent.
Definitions of Terms Related to Home Water Systems
meter is located inside the home, the company providing
the water must make appointments to read the meter,
which often results in higher water costs unless the meter
is equipped with a signal that can be observed from the
outside. The water meter is not shown in Figure 9.2
because of regional differences in location of the unit.
Because the electric system is sometimes grounded to an
older home’s water line, a grounding loop device should
be installed around the meter. Many meters come with a
yoke that maintains electrical continuity even though the
meter is removed.
Healthy Housing Reference Manual9-4 Chapter 9: Plumbing
Hot and Cold Water Main Lines
The hot and cold water main lines are usually hung from
the basement ceiling or in the crawl space of the home
and are attached to the water meter and hot water tank
on one side and the fixture supply risers on the other.
These pipes should be installed neatly and should be supported by pipe hangers or straps of sufficient strength and
number to prevent sagging. Older homes that have copper pipe with soldered pipes can pose a lead poisoning
risk, particularly to children. In 1986, Congress banned
lead solder containing greater than 0.2% lead and
restricted the lead content of faucets, pipes, and other
plumbing materials to no more than 8%. The water should
be tested to determine the presence or level of lead in the
water. Until such tests can be conducted, the water should
be run for about 2 minutes in the morning to flush any
such material from the line. Hot and cold water lines
should be approximately 6 inches apart unless the hot
water line is insulated. This is to ensure that the cold water
line does not pick up heat from the hot water line [2].
The supply mains should have a drain valve stop and
waste valve to remove water from the system for repairs.
These valves should be on the low end of the line or on
the end of each fixture riser.
The fixture risers start at the basement main and rise vertically to the fixtures on the upper floors. In a one-family
dwelling, riser branches will usually proceed from the
main riser to each fixture grouping. In any event, the fixture risers should not depend on the branch risers for
support, but should be supported with a pipe bracket.
Storm sewer— A sewer used for conveying rain water, surface water, condensate, cooling water, or similar liquid waste.
Trap— A fitting or device that provides a liquid seal to prevent the emission of sewer gases without materially affecting the
flow of sewage or wastewater through it.
Vacuum breaker— A device to prevent backflow (back siphonage) by means of an opening through which air may be drawn
to relieve negative pressure (vacuum).
Vapor lock— A bubble of air that restricts the flow of water in a pipe.
Vent stack— The vertical vent pipe installed to provide air circulation to and from the drainage system and that extends
through one or more stories.
Water hammer— The loud thump of water in a pipe when a valve or faucet is suddenly closed.
Water service pipe— The pipe from the water main or other sources of potable water supply to the water-distributing
system of the building served.
Water supply system— Consists of the water service pipe, the water-distributing pipes, the necessary connecting pipes, fittings, control valves, and all appurtenances in or adjacent to the building or premises.
Wet vent— A vent that receives the discharge of waste other than from water closets.
Yoke vent— A pipe connecting upward from a soil or waste stack to a vent stack to prevent pressure changes in the stacks.
Definitions of Terms Related to Home Water Systems
The size of basement mains and risers depends on the
number of fixtures supplied. However, a ¾-inch pipe is
usually the minimum size used. This allows for deposits
on the pipe due to hardness in the water and will usually
give satisfactory volume and pressure.
In homes without basements, the water lines are preferably located in the crawl space or under the slab. The
water lines are sometimes placed in the attic; however,
because of freezing, condensation, or leaks, this placement can result in major water damage to the home. In
two-story or multistory homes, the water line placement
for the second floor is typically between the studs and,
then, for the shortest distance to the fixture, between the
joists of the upper floors.
Hot and Cold Water Piping Materials
Care must be taken when choosing the piping materials.
Some state and local plumbing codes prohibit using some
of the materials listed below in water distribution
systems.
Polyvinyl Chloride (PVC). PVC is used to make plastic
pipe. PVC piping has several applications in and around
homes such as in underground sprinkler systems, piping
for swimming pool pumping systems, and low-pressure
drain systems. PVC piping is also used for water service
between the meter and building [3]. PVC, or polyvinyl
chloride, is one of the most commonly used materials in
the marketplace. It is in packaging, construction and
automotive material, toys, and medical equipment.
9-5Chapter 9: PlumbingHealthy Housing Reference Manual
Chlorinated PVC (CPVC). CPVC is a slightly yellow
plastic pipe used inside homes. It has a long service life,
but is not quite as tough as copper. Some areas with corrosive water will benefit by using chlorinated PVC piping. CPVC piping is designed and recommended for use
in hot and cold potable water distribution systems [4].
Copper. Copper comes in three grades:
• M for thin wall pipe (used mainly inside homes);
• L for thicker wall pipe (used mainly outside for water
services); and
• K, the thickest (used mainly between water mains and
the water meter).
Copper lasts a long time, is durable, and connects well to
valves. It should not be installed if the water has a pH of
6.5 or less. Most public utilities supply water at a pH
between 7.2 and 8.0. Many utilities that have source
water with a pH below 6.5 treat the water to raise the
pH. Private well water systems often have a pH below
6.5. When this is the case, installing a treatment system
to make the water less acidic is a good idea [5].
Galvanized Steel. Galvanized pipe corrodes rather easily.
The typical life of this piping is about 40 years. One of
the primary problems with galvanized steel is that, in saturated water, the pipe will become severely restricted by
corrosion that eventually fills the pipe completely.
Another problem is that the mismatch of metals between
the brass valves and the steel results in corrosion.
Whenever steel pipe meets copper or brass, the steel pipe
will rapidly corrode. Dielectric unions can be used
between copper and steel pipes; however, these unions
will close off flow in a short time. The problem with
dielectric unions is that they break the grounding effect if
a live electrical wire comes in contact with a pipe. Some
cities require the two pipes to be bonded electrically to
maintain the safety of grounded pipes.
PEX. PEX is an acronym for a cross-formulated polyethylene. “PE” refers to the raw material used to make PEX
(polyethylene), and “X” refers to the cross-linking of the
polyethylene across its molecular chains. The molecular
chains are linked into a three-dimensional network that
makes PEX remarkably durable within a wide range of
temperatures, pressures, and chemicals [6].
PEX is flexible and can be installed with fewer fittings
than rigid plumbing systems. It is a good choice for
repiping and for new homes and works well for corrosive
water conditions. PEX stretches to accommodate the
expansion of freezing water and then returns to its original size when water thaws. Although it is highly freezeresistant, no material is freeze-proof.
Kitec. Kitec is a multipurpose pressure pipe that uniquely
unites the advantages of both metal and plastic. It is
made of an aluminum tube laminated to interior and
exterior layers of plastic. Kitec provides a composite piping system for a wide range of applications, often beyond
the scope of metal or plastic alone. Unlike copper and
steel materials, Kitec is noncorroding and resists most
acids, salt solutions, alkalis, fats, and oils.
Poly. Poly pipe is a soft plastic pipe that comes in coils
and is used for cold water. It can crack with age or wear
through from rocks. Other weak points can be the stainless steel clamps or galvanized couplings.
Polybutylene [Discontinued]. Polybutylene pipe is a soft
plastic pipe. This material is no longer recommended
because of early chemical breakdown. Individuals with a
house, mobile home, or other structure that has polybutylene piping with acetal plastic fittings may be eligible
for financial relief if they have replaced that plumbing
system. For claims information, call 1-800-392-7591 or
go to www.pbpipe.com.
Hot Water Safety
In the United States, more than 112,000 people enter a
hospital emergency room each year with scald burns. Of
these, 6,700 (6%), have to be hospitalized. Almost 3,000
of these scald burns come from tap water in the home.
The three high risk groups are children under the age of
5 years, the handicapped, and adults over the age of 65
years. It only takes 1 second to get a serious third-degree
burn from water that is 156°F (69°C). Tap water is too
hot if instant coffee granules melt in it.
Young children, some handicapped individuals, and
elderly people are particularly vulnerable to tap water
burns. Children cannot always tell the hot water faucets
from the cold water faucets. Children have delicate skin
and often cannot get out of hot water quickly, so they
suffer hot water burns most frequently. Elderly and handicapped persons are less agile and more prone to falls in
the bath tub. They also may have diseases, such as diabetes, that make them unable to feel heat in some regions of
the body, such as the hands and feet. Third-degree burns
can occur quickly— in 1 second at 156°F (69°C), in 2
seconds at 149°F (65°C), in 5 seconds at 140°F (60°C),
and in 15 seconds at 133°F (56°C).
A tap-water temperature of 120°F–130°F (49°C–54°C) is
hot enough for washing clothes, bedding, and dishes.
Even at 130°F (54°C), water takes only a few minutes of
constant contact to produce a third-degree burn. Few
people bathe at temperatures above 110°F (43°C), nor
Healthy Housing Reference Manual9-6 Chapter 9: Plumbing
should they. Water heater thermostats should be set at
about 120°F (49°C) for safety and to save 18% of the
energy used at 140°F (60°C). Antiscald devices for faucets
and showerheads to regulate water temperature can help
prevent burns. A plumber should install and calibrate
these devices. Most hot water tank installations now
require an expansion tank to reduce pressure fluctuations
and a heat trap to keep hot water from escaping up pipes.
Types of Water Flow Controls
It is essential that valves be used in a water system to
allow the system to be controlled in a safe and efficient
manner. The number, type, and size of valves required
will depend on the size and complexity of the system.
Most valves can be purchased in sizes and types to match
the pipe sizes used in water system installations. Listed
below are some of the more commonly encountered
valves with a description of their basic functions.
Shutoff Valves. Shutoff valves should be installed
between the pump and the pressure tank and between the
pressure tank and service entry to a building. Globe, gate,
and ball valves are common shutoff valves. Gate and ball
valves cause less friction loss than do globe valves; ball
valves last longer and leak less than do gate valves.
Shutoff valves allow servicing of parts of the system without draining the entire system.
Flow-control Valves. Flow-control valves provide uniform flow at varying pressures. They are sometimes
needed to regulate or limit the use of water because of
limited water flow from low-yielding wells or an inadequate pumping system. They also may be needed with
some treatment equipment. These valves are often used to
limit flow to a fixture. Orifices, mechanical valves, or diaphragm valves are used to restrict the flow to any one service line or complete system and to assure a minimum
flow rate to all outlets.
Relief Valves. Relief valves permit water or air to escape
from the system to relieve excess pressure. They are
spring-controlled and are usually adjustable to relieve
varying pressures, generally above 60 psi. Relief valves
should be installed in systems that may develop pressures
exceeding the rated limits of the pressure tank or distribution system. Positive displacement and submersible
pumps and water heaters can develop these excessive pressures. The relief valve should be installed between the
pump and the first shutoff valve and must be capable of
discharging the flow rate of the pump. A combined pressure and temperature relief valve is needed on all water
heaters. Combination pressure and vacuum relief valves
also should be installed to prevent vacuum damage to the
system.
Pressure-reducing Valves. A pressure-reducing valve is
used to reduce line pressure. On main lines, this allows
the use of thinner walled pipe and protects house plumbing. Sometimes these valves are installed on individual
services to protect plumbing.
Altitude Valves. Often an altitude valve is installed at the
base of a hot water tank to prevent it from overflowing.
Altitude valves sense the tank level through a pressure line
to the tank. An adjustable spring allows setting the level
so that the valve closes and prevents more inflow when
the tank becomes full.
Foot Valves. A foot valve is a special type of check valve
installed at the end of a suction pipe or below the jet in a
well to prevent backflow and loss of prime. The valve
should be of good quality and cause little friction loss.
Check Valves. Check valves have a function similar to foot
valves. They permit water flow in only one direction
through a pipe. A submersible pump may use several check
valves. One is located at the top of the pump to prevent
backflow from causing back spin of the impellers. Some
systems use another check valve and a snifter valve. They
will be in the drop pipe or pitless unit in the well casing
and allow a weep hole located between the two valves to
drain part of the pipe. When the pump is started, it will
force the air from the drained part of the pipe into the
pressure tank, thus recharging the pressure tank.
Frost-proof Faucets. Frost-proof faucets are installed outside a house with the shutoff valve extending into the
heated house to prevent freezing. After each use, the
water between the valve and outlet drains, provided the
hose is disconnected, so water is not left to freeze.
Frost-proof Hydrants. Frost-proof hydrants make outdoor water service possible during cold weather without
the danger of freezing. The shutoff valve is buried below
the frost line. To avoid submerging it, which might result
in contamination and back siphoning, the stop-and-waste
valve must drain freely into a rock bed. These hydrants
are sometimes prohibited by local or state health
authorities.
Float Valves. Float valves respond to a high water level to
close an inlet pipe, as in a tank-type toilet.
Miscellaneous Switches. Float switches respond to a
high and/or low water level as with an intermediate storage tank. Pressure switches with a low-pressure cutoff
stop the pump motor if the line pressure drops to the
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cutoff point. Low-flow cutoff switches are used with submersible pumps to stop the pump if the water discharge
falls below a predetermined minimum operating pressure.
High-pressure cut-off switches are used to stop pumps if
the system pressure rises above a predetermined maximum. Paddle-type flow switches detect flow by means of
a paddle placed in the pipe that operates a mechanical
switch when flow in the pipe pushes the paddle.
The inadvertent contamination of a public water supply
as a result of incorrectly installing plumbing fixtures is a
potential public health problem in all communities.
Continuous surveillance by environmental health personnel is necessary to know whether such public health hazards have developed as a result of additions or alterations
to an approved system. All environmental health specialists should learn to recognize the three general types of
defects found in potable water supply systems: back flow,
back siphonage, and overhead leakage into open potable
water containers. If identified, these conditions should be
corrected immediately to prevent the spread of disease or
poisoning from high concentrations of organic or inorganic chemicals in the water.
Water Heaters
Water heaters (Figure 9.3) are usually powered by electricity, fuel oil, gas, or, in rare cases, coal or wood. They
consist of a space for heating the water and a storage tank
for providing hot water over a limited period of time. All
water heaters should be fitted with a temperature-pressure
(T&P) relief valve no matter what fuel is used. The
installation port for these valves may be found on the top
or on the side of the tank near the top. T&P valves
should not be placed close to a wall or door jamb, where
they would be inaccessible for inspection and use. Hot
water tanks sometimes are sold without the T&P valve,
and it must be purchased separately. This fact alone
should encourage individual permitting and inspection by
counties and municipalities to ensure that they are
installed. The T&P valve should be inspected at a minimum of once per year.
A properly installed T&P valve will operate when either
the temperature or the pressure becomes too high due to
an interruption of the water supply or a faulty thermostat. Figure 9.3 shows the correct installation of a gas
water heater. Particular care should be paid to the exhaust
port of the T&P valve. Figure 9.4 shows the placement of
the T&P valve. This vent should be directed to within 6
inches of the floor, and care must be taken to avoid
reducing the diameter of the vent and creating any
unnecessary bends in the discharge pipe. Most codes will
Figure 9.3. Gas Water Heater [1]
allow only one 90° bend in the vent. The point is to
avoid any constrictions that could slow down the steam
release from the tank to avoid explosive pressure buildup.
Water heaters that are installed on wooden floors should
have water collection pans with a drainage tube that
drains to a proper drain. The pan should be checked on a
regular basis.
Tankless Water Heaters
A tankless unit has a heating device that is activated by
the flow of water when a hot water valve is opened. Once
activated, the heater delivers a constant supply of hot
water. The output of the heater, however, limits the rate
of the heated water flow. Demand water heaters are available in propane (LP), natural gas, or electric models.
They come in a variety of sizes for different applications,
such as a whole-house water heater, a hot water source for
a remote bathroom or hot tub, or as a boiler to provide
hot water for a home heating system. They can also be
used as a booster for dishwashers, washing machines, and
a solar or wood-fired domestic hot water system [7].
The appeal of demand water heaters is not only the elimination of the tank standby losses and the resulting lower
operating costs, but also the fact that the heater delivers
hot water continuously. Most tankless models have a life
Healthy Housing Reference Manual9-8 Chapter 9: Plumbing
expectancy of more than 20 years. In contrast, storage
tank water heaters last 10 to 15 years. Most tankless
models have easily replaceable parts that can extend their
life by many years more.
Drainage System
Water is brought into a house, used, and discharged
through the drainage system. This system is a sanitary
drainage system carrying just interior wastewater.
Sanitary Drainage System
The proper sizing of the sanitary drain or house drain
depends on the number of fixtures it serves. The usual
minimum size is 4 inches in diameter. The materials used
are usually cast iron, vitrified clay, plastic, and, in rare
cases, lead. The top two pipe choices for drain, waste, and
vent (DWV) systems are PVC or ABS. For proper flow in
the drain, the pipe should be sized and angled so that the
pipe is approximately half full. This ensures proper scouring action so that the solids contained in the waste will
not be deposited in the pipe.
Using PVC in DWV pipe is a two-step process needing a
primer and then cement. ABS uses cement only. In most
cases the decision will be made on the basis of which
material is sold in an area. Few areas stock both materials
because local contractors usually favor one or the other.
Figure 9.4. Temperature-Pressure Valve
ABS costs more than PVC in many areas, but Schedule
40 PVC DWV solid core pipe is stronger than ABS.
Their durability is similar.
Size of House Drain. The Uniform Plumbing Code
Committee has developed a method of sizing house
drains in terms of fixture units. One fixture unit equals
approximately 7½ gallons of water per minute. This is
the surge flow rate of water discharged from a wash basin
in one minute.
All other fixtures have been related to this unit. Fixture
unit values are shown in Table 9.1.
Grade of House Drain. A house drain should be sloped
toward the sewer to ensure scouring of the drain. The
usual pitch of a house or building sewer is a ¼-inch drop
in 1 foot of length. The size of the drain is based on the
fixture units flowing into the pipe and the slope of the
drain. Table 9.2 shows the required pipe size for the
system.
House Drain Installation. Typical branch connections to
the main are shown in Figure 9.5.
Fixture and Branch Drains. A branch drain is a waste
pipe that collects the waste from two or more fixtures and
conveys it to the sewer. It is sized in the same way as the
sewer, taking into account that all toilets must have a
minimum 3-inch diameter drain, and only two toilets
may connect into one 3-inch drain. All branch drains
must join the house drain with a Y-fitting as shown in
Figure 9.5. The same is true for fixture drains joining
branch drains. The Y-fitting is used to eliminate, as much
as possible, the deposit of solids in or near the connection. A buildup of these solids will block the drain.
Recommended minimum sizes of fixture drains are
shown in Table 9.2.
Traps
A plumbing trap is a device used in a waste system to
prevent the passage of sewer gas into the structure and yet
not hinder the fixture’s discharge to any great extent. All
fixtures connected to a household plumbing system
should have a trap installed in the line. The effects of
sewer gases on the human body are well known; many of
the gases are extremely harmful. In addition, certain
sewer gases are explosive.
P-trap. The most commonly used trap is the P-trap
(Figure 9.6). The depth of the seal in a trap is usually 2
inches. A deep seal trap has a 4-inch seal.
9-9Chapter 9: PlumbingHealthy Housing Reference Manual
As mentioned earlier, the purpose of a trap is to seal out
sewer gases from the structure. Because a plumbing
system is subject to wide variations in flow, and this flow
originates in many different sections of the system,
pressures vary widely in the waste lines. These pressure
differences tend to remove the water seal in the trap. The
waste system must be properly vented to prevent the traps
from siphoning dry, thus losing their water seal and
allowing gas from the sewer into the building.
Objectionable Traps. The S-trap and the ¾ S-trap
(Figure 9.7) should not be used in plumbing installations.
They are almost impossible to ventilate properly, and the
¾ S-trap forms a perfect siphon. Mechanical traps were
introduced to counteract this problem. It has been found,
however, that the corrosive liquids flowing in the system
corrode or jam these mechanical traps. For this reason,
most plumbing codes prohibit mechanical traps.
The bag trap, an extreme form of S-trap, is seldom found.
Figure 9.7 also shows this type of S-trap.
Traps are used only to prevent the escape of sewer gas
into the structure. They do not compensate for pressure
variations. Only proper venting will eliminate pressure
problems.
Ventilation
A plumbing system is ventilated to prevent trap seal loss,
material deterioration, and flow retardation.
Trap Seal Loss. The seal in a plumbing trap may be lost
due to siphonage (direct and indirect or momentum),
back pressure, evaporation, capillary attraction, or wind
effect. The first two are probably the most common
causes of loss. Figure 9.8 depicts this siphonage process;
Figure 9.9 depicts loss of trap seal.
If a waste pipe is placed vertically after the fixture trap, as
in an S-trap, the wastewater continues to flow after the
fixture is emptied and clears the trap. This is caused by
the pressure of air on the water of the fixture being
greater than the pressure of air in the waste pipe. The
action of the water discharging into the waste pipe
removes the air from that pipe and thereby causes a negative pressure in the waste line.
Fixture Units
Lavatory/washbasin 1
Kitchen sink 2
Bathtub 2
Laundry tub 2
Combination fixture 3
Urinal 5
Shower bath 2
Floor drain 1
Slop sink 3
Toilet 6 or 3 (based on type)
One bathroom group 8
180 square feet of roof 1
Table 9.1. Fixture Unit Values
Diameter of
Pipe, Inches
Maximum Number of Fixtures per Listed Drain Slope†
¹⁄8 inch per foot ¼ inch per foot ½ inch per foot
1¼ 1 1 1
1½ 2 2 3
2 5 6 8
3 15 18 21
4 84 96 114
6 300 450 600
8 990 1,392 2,220
12 3,084 4,320 6,912
† Number of fixture units.
Table 9.2. Sanitary House Drain Sizes
Healthy Housing Reference Manual9-10 Chapter 9: Plumbing
In the case of indirect or momentum siphonage, the flow
of water past the entrance to a fixture drain in the waste
pipe removes air from the fixture drain. This reduces the
air pressure in the fixture drain, and the entire assembly
acts as an aspirator. (Figures 9.10 and 9.11 show plumbing configurations that would allow this type of siphonage
to occur.)
Back Pressure. The flow of water in a soil pipe varies
according to the fixtures being used. Small flows tend to
cling to the sides of the pipe, but large ones form a slug of
waste as they drop. As this slug of water falls down the
pipe, the air in front of it becomes pressurized. As the pressure builds, it seeks an escape point. This point is either a
vent or a fixture outlet. If the vent is plugged or there is no
vent, the only escape for this air is the fixture outlet.
The air pressure forces the trap seal up the pipe into the fixture. If the pressure is great enough, the seal is blown out of
the fixture entirely. Figures 9.8 and 9.9 illustrate the potential for this type of problem. Large water flow past the vent
can aspirate the water from the trap, while water flow
approaching the trap can blow the water out of the trap.
Figure 9.7. Types of S-traps
Figure 9.8. Trap Seal:
[a] Seal Intact;
[b] Fixture Draining;
[c] Loss of Gas Seal [1]
Figure 9.5. Branch Connections Figure 9.6. P-trap [1]
Vent Sizing. Vent pipe installation
is similar to that of soil and waste
pipe. The same fixture unit criteria
are used. Table 9.3 shows minimum vent pipe sizes.
Vent pipes of less than 1¼ inches
in diameter should not be used.
Vents smaller than this diameter
tend to clog and do not perform
their function.
Individual Fixture Ventilation.
Figure 9.12 shows a typical installation of a wall-hung plumbing
unit. This type of ventilation is
generally used for sinks, drinking
fountains, and so forth. Air admittance valves are often used for
individual fixtures. Figure 9.13
shows a typical installation of a
bathtub or shower ventilation system. Figure 9.14 shows the proper
vent connection for toilet fixtures
and Figure 9.15 shows a janitor’s
sink or slop sink that has the
proper P-trap. For the plumbing
fixture to work properly, it must
be vented as in Figures 9.13 and
9.14.
Unit Venting. Figures 9.10 and
9.11 show a back-to-back shared
ventilation system for various
plumbing fixtures. The unit vent9-11Chapter 9: PlumbingHealthy Housing Reference Manual
ing system is commonly
used in apartment buildings. This type of system
saves a great deal of money
and space when fixtures are
placed back-to-back in separate apartments. It does,
however, pose a problem if
the vents are undersized
because they will aspirate
the water from the other
trap. Figure 9.16 shows a
double combination Y-trap
used for joining the fixtures
to the common soil pipe
fixture on the other side of
the wall.
Wet Venting. Bathroom fixture groupings are commonly wet vented; that is,
the vent pipe also is used as
a waste line.
Total Drainage System
The drain, soil waste, and vent systems are all connected,
and the inspector should remember the following
fundamentals:
Working vents must provide air to all fixtures to ensure
the movement of waste into the sewer. Improperly vented
fixtures will drain slowly and clog often. They also present a health risk if highly toxic and explosive sewer gases
enter the home. Correct venting is shown in Figures
9.10–9.15; incorrect venting is shown in Figures 9.8 and
9.9. A wet vent can result in one of the traps siphoning
the other dry when large volumes of water are poured
down the drain. Wet vents are not permitted by many
state plumbing codes because of the potential for
self-siphoning.
Backup of sewage into sinks, dishwashers, and other
appliances is always a possibility unless the system is
equipped with air gaps or vacuum breakers. All connections to the potable water system must be a minimum of
two pipe diameters above the overflow of the appliance
and, in some cases, where flat surfaces are near, two and
one-half pipe diameters above the overflow of the
appliance.
A simple demonstration of how easily siphoning can
occur is to hold a glass of water with food coloring in it
with the tip of a faucet in the colored water. If the sink’s
Figure 9.9. Loss of Trap Seal in
Lavatory Sink [1]
Figure 9.10. Back-to-back Venting [Toilet]
Figure 9.11. Back-to-back Venting [Sink]
vegetable sprayer is directed to a second glass and sprayed,
in most cases, the colored water will be aspirated into the
faucet and then out of the sprayer into the second glass.
Weed or pest killer attachments that hook to garden hoses
work on the same principle. Figure 9.17 shows an outside
hose bib equipped with a vacuum breaker. In the areas of
the United States that freeze, these vacuum breakers must
be removed because they trap water in the area of the line
that can freeze and burst. Many vacuum breakers sold
today automatically drain to prevent freeze damage.
Healthy Housing Reference Manual9-12 Chapter 9: Plumbing
Devices that pull water from a utility may create negative
pressures that can damage water piping and pull dangerous substances into the line at the same time. These
devices include power sprayers that hook to the home
hose bib (outside faucets) and pressurize the spray by
creating a vacuum on the supply side.
Corrosion Control
To understand the proper maintenance procedures for the
prevention and elimination of water quality problems in
plumbing systems, it is necessary to understand the process used to determine the chemical aggressiveness of
water. The process is used to determine when additional
treatment is needed. Water that is out of balance can
result in many negative outcomes, from toxic water to
damaged and ruined equipment.
Water dissolves and carries materials when it is not saturated. An equilibrium among pH, temperature, alkalinity,
and hardness controls water’s ability to create scale or to
dissolve material. If water is saturated with harmless or
beneficial substances, such as calcium, then the threat of
damage can be mitigated. The Langelier method, developed in the early 1930s, is a process used in boiler management, municipal water treatment, and swimming
pools to provide this balance. In the Langelier index, saturation over 0.3 is scale forming, and a saturation below
0.3 is corrosive.
Figure 9.12. Wall-hung Fixtures
Figure 9.13. Unit Vent Used in Bathtub Installation
Fixture Supply Line, Inches Vent Line, Inches Drain Line, Inches
Bathtub 1/2 11/2 11/2
Kitchen sink 1/2 11/2 11/2
Lavatory 3/8 11/4 11/4
Laundry sink 1/2 11/2 11/2
Shower 1/2 2 2
Toilet tank 3/8 3 3
Table 9.3. Minimum Fixture Service Pipe Diameters
Figure 9.14. Toilet Venting
9-13Chapter 9: PlumbingHealthy Housing Reference Manual
According to the
EPA, in 2000, a typical U.S. family of
four spent approximately $820 every
year on water and
sewer fees, plus
another $230 in
energy for heating
water. In many cities, according to the U.S. EPA, water
and sewer costs can be more than twice those amounts.
Many people do not realize how much money they can
save by taking simple steps to save water, and they do not
know the cumulative effects small changes can have on
water resources and environmental quality. Fixing a leaky
faucet, toilet, or lawn-watering system can reduce water
consumption. Changing to water-efficient plumbing
fixtures and appliances can result in major water and
energy savings [9,10].
Summer droughts remind many of the need to appreciate
clean water as an invaluable resource. As the U.S. population increases, the need for clean water supplies continues
to grow dramatically and puts additional stress on our
limited water resources. We can all take steps to save and
conserve this valuable resource.
The EPA [11] suggests the following steps homeowners
should take right away to save water and money:
• Stop leaks!— Check indoor water-using appliances
and devices for leaks. Pay particular attention to toilets
that leak.
• Take showers— Showers use considerably less water
than do baths.
• Replace shower heads— Replacement shower heads
are available that reduce water use.
• Turn the water off when not needed— While
brushing your teeth, turn the water off until you need
to rinse.
• Replace your old toilet— The largest water user inside
the home is the toilet. If a home was built before 1992
and the toilet has never been replaced, it is very likely
that it is not a water-efficient, 1.6 gallons-per-flush
toilet. Choose a replacement toilet carefully to ensure
that what you make up per individual flush, you do
not lose because you must flush more often.
• Replace your clothes washer— The second largest
water user in the home is the washing machine. Energy
Star-rated washers that also have a water factor at or
The susceptibility of metal to corrosion is as follows
(most susceptible to least susceptible): magnesium, zinc,
aluminum, cadmium, mild steel, cast iron, stainless steel
(active), lead-tin solder, lead, tin, brass, gun metal, aluminum bronze, copper, copper-nickel alloy, Monel, titanium,
stainless steel (passive), silver, gold, and platinum.
Water Conservation
How much attention should be paid to fixtures that just
drip a little bit of water or that just will not quite shut
off? At 30 drops per minute, you will lose and pay for 54
gallons per month. At 60 drops per minute, you will lose
and pay for 113 gallons per month. At 120 drops per
minute, you will lose and pay for 237 gallons per month.
This is only a small loss of water considering the 5 to 7
gallons per flush used by a properly functioning toilet. If
the toilet is not properly maintained, the loss of water and
its effect on the monthly water bill can be incredible.
Lower flow toilets have been mandated to save precious
and limited resources. Most pre-1992 toilets used up to 7
gallons per flush. Toilets have since evolved to use 5.5,
then 3.5, and now 1.6 gallons per flush.
With the changes in the water usage laws in 1992, there
were many customer
complaints, and plumbers were in the bad position of installing
products that nobody
wanted to use. New and
updated products now
work better than the old
water wasters.
Figure 9.15. Janitor’s Sink
Figure 9.16. Common Y-trap
Figure 9.17. Hose Bib With Vacuum Breaker
Healthy Housing Reference Manual9-14 Chapter 9: Plumbing
lower than 9.5 use 35%–50% less water and 50% less
energy per load. This saves money on both water and
energy bills.
• Plant the right plants with proper landscape design
and irrigation— Select plants that are appropriate for
the local climate. Having a 100% turf lawn in a dry
desert climate uses a significant amount of water. Also,
home owners should consider the benefits of a more
natural landscape or wildscape.
• Water plants only as needed— Most water wasted in
the garden is by watering when plants do not need it
A.
Hot and cold copper water lines and drain, p-trap and
vent, and vent for the washer drain shown. When a
house is vacant for awhile, the P-trap should be filled
with water to prevent sewer gas from entering the
home. Mineral oil added to the water can slow the loss
of fluid in the trap.
B.
Hot and cold water pipes, soil pipe, and vent shown.
C.
Vent for the sink and toilet, soil pipe, and cap for
toilet connection shown. A wax or plastic seal shaped
like a donut will be placed on the cap before bolting
down the toilet.
or by not maintaining the irrigation system. If
manually watering, set a timer and move the hose
promptly. Make sure the irrigation controller has a
rain shutoff device and that it is appropriately
scheduled. Drip irrigation should be considered where
practical. Newer irrigation systems have sensors to
prevent watering while it is raining.
Putting It All Together
These photographs, taken during construction of a home
by Habitat for Humanity, show various plumbing elements discussed in this chapter.
9-15Chapter 9: PlumbingHealthy Housing Reference Manual
D.
Mixing and antiscald water flow control, vent for
fixture, hot and cold water lines, and bathtub overflow
shown. At this point in construction, insulation might
be considered for the hot water lines. Water service
and waste water line.
E.
Polyethylene water service pipe entering the home
through the concrete basement wall shown. White
plastic adapter shown between polyethylene water
service pipe and ¾ inch copper water line. A short
distance above the adapter is a pressure reducing valve.
To the right of water line is the 4-inch PVC pipe waste
water line.
References
1. US Environmental Protection Agency. United States
Environmental Protection Agency guidance from hotline
compendium: lead ban. Washington, DC: US
Environmental Protection Agency; 1988. Available from
URL: http://www.epa.gov/safewater/wsg/wsg_H19.pdf.
2. Uni-Bell PVC Pipe Association. Handbook of PVC pipe
design and construction. Dallas: Uni-Bell PVC Pipe
Association; 2001. Available from URL: http://www.
uni-bell.org/pubs/handbook.pdf.
3. Occupational Safety and Health Administration. Safety
hazard information bulletin on the use of polyvinyl
chloride (PVC) pipe in above ground installations.
Washington, DC: Occupational Safety and Health
Administration; 1988. http://www.osha.gov/dts/hib/hib_
data/hib19880520.html.
4. Copper Development Association. Copper in your home:
plumbing, heating, cooling. New York: Copper
Development Association; no date. Available from URL:
http://www.copper.org/copperhome/PHC/phc_home.html.
5. Plastic Pipe and Fittings Association. Cross-linked
polyethylene. Glen Ellyn, IL: Plastic Pipe and Fittings
Association; no date. Available from URL: http://www.
ppfahome.org/pex/historypex.html.
6. NAMCO. Determine the total fixture unit load. Dallas:
NAMCO; no date. Available from URL: http://www.
namco-div.com/booster/sel%20criteria/fixtureload.htm.
7. Energy Efficiency and Renewable Energy Clearinghouse.
Demand (tankless or instantaneous) water heaters.
Merrifield, VA: Energy Efficiency and Renewable Energy
Clearinghouse; no date. Available from URL:
http://www.toolbase.org/tertiaryT.asp?DocumentID=3206
&&&CategoryID=0.
Healthy Housing Reference Manual9-16 Chapter 9: Plumbing
8. Public Health-Seattle and King County. Public health
plumbing program: water supply fixture units (WSFU)
and minimum fixture branch pipe sizes. Seattle, WA:
Public Health-Seattle and King County; no date. Available
from URL: http://www.metrokc.gov/health/plumbing/
wsfu.htm.
9. US Environmental Protection Agency. Developing water
system financial capacity. Washington, DC: US
Environmental Protection Agency; 2002. Available from
URL: http://www.epa.gov/safewater/dwa/electronic/
presentations/pwsoper/fincapacity.pdf.
10. US Environmental Protection Agency. Water and
wastewater pricing. Washington, DC: US Environmental
Protection Agency; no date. Available from URL:
http://www.epa.gov/water/infrastructure/pricing/.
11. US Environmental Protection Agency. Using water wisely
in the home. Washington, DC: US Environmental
Protection Agency; 2002. Available from URL:
http://www.epa.gov/owm/water-efficiency/
waterconservation_final.pdf.
Additional Sources of Information
American Backflow Prevention Association. Available
from URL: http://www.abpa.org.
American Society of Plumbing Engineers. Available from
URL: http://aspe.org.
American Society of Sanitary Engineering. Available from
URL: http://www.asse-plumbing.org.
American Water Works Association. Available from URL:
http://www.awwa.org.
National Sanitation Foundation. Available from URL:
http://www.nsf.org/international.
Plumbing-Heating-Cooling Contractors Association.
Available from URL: http://www.phccweb.org.
Underwriters Laboratories Inc. Available from URL:
http://www.ul.com.
For more water conservation tips and energy saving ideas
for businesses, industries, and individuals, visit the EPA’s
Water-use Efficiency Program Web site (http://www.epa.
gov/owm/water-efficiency/index.htm).
10-1Chapter 10: On-site Wastewater TreatmentHealthy Housing Reference Manual
“Technology has made large populations possible;
large populations now make technology indispensable.”
Joseph Wood Krutch, Author, 1932
Introduction
The French are considered the first to use an underground septic tank system in the 1870s. By the mid
1880s, two-chamber, automatic siphoning septic tank systems, similar to those used today, were being installed in
the United States. Even now, more than a century later,
septic tank systems represent a major household wastewater treatment option. Fully one-fourth to one-third of the
homes in the United States use such a system [1].
On-site sewage disposal systems are used in rural areas
where houses are spaced so far apart that a sewer system
would be too expensive to install, or in areas around cities
where the city government has not yet provided sewers to
which the homes can connect. In these areas, people
install their own private sewage treatment plants. As populations continue to expand beyond the reach of municipal sewer systems, more families are relying on individual
on-site wastewater treatment systems and private water
supplies. The close proximity of on-site water and wastewater systems in subdivisions and other developed areas,
reliance on marginal or poor soils for on-site wastewater
disposal, and a general lack of understanding by homeowners about proper septic tank system maintenance pose
a significant threat to public health. The expertise on
inspecting, maintaining, and installing these systems generally rests with the environmental health staff of the
local county or city health departments.
These private disposal systems are typically called septic
tank systems. A septic tank is a sewage holding device
made of concrete, steel, fiberglass, polyethylene, or other
Chapter 10: On-site Wastewater Treatment
Figure 10.1. Conventional On-site Septic System [2]
Effluent leaves home through a pipe, enters a septic tank, travels through a
distribution box to a trench absorption system composed of perforated pipe.
approved material cistern, buried in a yard, which may
hold 1,000 gallons or more of wastewater. Wastewater
flows from the home into the tank at one end and leaves
the tank at the other (Figure 10.1) [2].
Proper maintenance of septic tanks is a public health
necessity. Enteric diseases such as cryptospordiosis, giardiasis, salmonellosis, hepatitis A, and shigellosis may be
transmitted through human excrement. Historically,
major epidemics of cholera and typhoid fever were primarily caused by improper disposal of wastewater. The
earliest epidemiology lesson learned was through the
effort of Dr. John Snow of England (1813–1858) during
a devastating cholera epidemic in London [3]. Dr. Snow,
known as the father of field epidemiology, discovered that
the city's water supply was being contaminated by
improper disposal of human waste. He published a brief
pamphlet, On the Mode of Communication of Cholera,
suggesting that cholera is a contagious disease caused by a
poison that reproduces in the human body and is found
in the vomitus and stools of cholera patients. He believed
that the main, although not only, means of transmission
was water contaminated with this poison. This differed
from the commonly accepted belief at the time that diseases were transmitted by inhaling vapors.
Treatment of Human Waste
Safe, sanitary, nuisance-free disposal of wastewater is a
public health priority in all population groups, small and
large, rural or urban. Wastewater should be disposed of in
a manner that ensures that
• community or private drinking water supplies are not
threatened;
• direct human exposure is not possible;
• waste is inaccessible to vectors, insects, rodents, or
other possible carriers;
• all environmental laws and regulations are complied
with; and
• odor or aesthetic nuisances are not created.
In Figure 10.2, a straight pipe from a nearby home
discharges untreated sewage that flows from a shallow
drainage ditch to a roadside mountain creek in which
many children and some adults wade and fish. The clear
water (Figure 10.3) is quite deceptive in terms of the
health hazard presented. A 4-mile walk along the creek
Healthy Housing Reference Manual10-2 Chapter 10: On-site Wastewater Treatment
revealed 12 additional pipes that were also releasing
untreated sewage. Some people in the area reportedly
regard this creek as a source of drinking water.
Raw or untreated domestic wastewater (sewage) is
primarily water, containing only 0.1% of impurities that
must be treated and removed. Domestic wastewater
contains biodegradable organic materials and, very likely,
pathogens. The primary purpose of wastewater treatment
is to remove impurities and release the treated effluent
into the ground or a stream. There are various processes
for accomplishing this:
Figure 10.2. Straight Pipe Discharge
Source: Donald Johnson; used with permission.
Figure 10.3. Clear Creek Water Contaminated With Sewage
Source: Donald Johnson; used with permission.
John Snow, a London physician, was among the first to
use anesthesia. It is his work in epidemiology, however,
that earned him his reputation as a prototype for epidemiologists. Dr. Snow’s brief 1849 pamphlet, On the Mode of
Communication of Cholera, caused no great stir, and his
theory that the city’s water supply was contaminated was
only one of many proposed during the epidemic.
Snow, however, was able to prove his theory in 1854, when
another severe epidemic of cholera occurred in London.
Through painstaking documentation of cholera cases and
correlation of the comparative incidence of cholera among
subscribers to the city’s two water companies, he showed
that cholera occurred much more frequently in customers
of one water company. This company drew its water from
the lower Thames, which become contaminated with
London sewage, whereas the other company obtained
water from the upper Thames. Snow’s evidence soon
gained many converts.
A striking incident during this epidemic has become legendary. In one neighborhood, the intersection of
Cambridge Street and Broad Street, the concentration of
cholera cases was so great that the number of deaths
reached over 500 in 10 days. Snow investigated the situation and concluded that the cases were clustered around
the Broad Street pump. He advised an incredulous but
panicked assembly of officials to have the pump handle removed, and when this was done, the epidemic was contained. Snow was a skilled practitioner as well as an epidemiologist, and his creative use of the scientific information
of his time is an appropriate example for those interested
in disease prevention and control [3].
Epidemiology
• Centralized treatment— Publicly owned treatment
works (POTWs) that use primary (physical) treatment
and secondary (biologic) treatment on a large scale to
treat flows of up to millions of gallons or liters per day,
• Treatment on-site— Septic tanks and absorption fields
or variations thereof, and
• Stabilization ponds (lagoons)— Centralized
treatment for populations of 10,000 or less when soil
conditions are marginal and land space is ample.
Not included are pit privies and compost toilets.
10-3Chapter 10: On-site Wastewater TreatmentHealthy Housing Reference Manual
Historically, wastewater disposal systems are categorized
as water-carrying and nonwater-carrying. Nonwatercarried human fecal waste can be contained and decomposed on-site, the primary examples being a pit privy or
compost toilet. These systems are not practical for individual residences because they are inconvenient and they
expose users to inclement weather, biting insects, and
odors. Because of the depth of the disposal pit for privies,
they may introduce waste directly into groundwater. It
should be noted that these types of systems are often used
and may be acceptable in low-water-use conditions such
as small campsites or along nature trails [4–6].
On-site Wastewater Treatment Systems
As urban sprawl continues and the population increases
in rural areas, the cost of building additional sewage disposal systems increases. One of the prime reasons for
annexation is to increase the tax base without increasing
the cost of municipal government. The governments
involved often buy into short-term tax gains at massive
long-term costs for eventual infrastructure improvements
to annexed communities. Installing septic tank systems is
common to provide on-site disposal systems, but it is a
temporary solution at best. Because property size must be
sufficient to allow space for septic system replacement,
the cost to the municipality installing a centralized sewer
system will be dramatically increased because of the large
lot size.
Two microbiologic processes occur in all methods that
attempt to decompose domestic wastewater: anaerobic
(by bacteria that do not require oxygen) and aerobic (by
bacteria that require oxygen) decomposition. Aerobic
decomposition is generally preferred because aerobic bacteria decompose organic matter (sewage) at a rate much
faster than do anaerobic bacteria and odors are less likely.
Centralized wastewater treatment facilities use aerobic
processes, as do most types of lagoons. Septic tank systems use both processes.
Septic Tank Systems
Approximately 21% of American homes are served by onsite sewage disposal systems. Of these, 95% are septic
tank field systems. Septic tank systems are used as a
means of on-site wastewater treatment in many homes,
both in rural and urban areas, in the United States. If
maintained and operated within acceptable parameters,
they are capable of properly treating wastewater for a limited number of years and will need both routine maintenance and eventually major repairs. Proper placement and
installation is a key to the successful operation of any onFigure 10.4. Septic Tank System [7]
site wastewater treatment system, but septic tank systems
have a finite life expectancy and all such systems will
eventually fail and need to be replaced. Figure 10.4 shows
a typical rural home with a well and a septic system.
Septic tank systems generally are composed of the septic
tank, distribution box, absorption field (also known as
the soil drain field), and leach field. The septic tank
serves three purposes: sedimentation of solids in the
wastewater, storage of solids, and anaerobic breakdown of
organic materials.
To place the septic tank and absorption field in a way
that will not contaminate water wells, groundwater, or
streams, the system should be 10 feet from the house and
other structures, at least 5 feet from property lines, 50
feet from water wells, and 25 feet from streams. The
entire system area should be easily identifiable. There
have been occasions when owners have paved or built
over the area. The local health code authorities must be
consulted on required distances in their area because of
soil and groundwater issues.
Aerobic, or aerated, septic systems use a suspended
growth wastewater treatment process, and can remove
suspended solids that are not removed by simple sedimentation. Under appropriate conditions, aerobic units
may also provide for nitrification of ammonia, as well as
significant pathogen reduction. Some type of primary
treatment usually precedes the aerated tank. The tanks
contain an aeration chamber, with either mechanical aerators or blowers, or air diffusers, and an area for final clarification/settling. Aerobic units may be designed as either
continuous flow or batch flow systems. The continuous
flow type are the most commercially available units.
Healthy Housing Reference Manual10-4 Chapter 10: On-site Wastewater Treatment
Effluent from the aerated tank is conveyed either by gravity flow or pumping to either further treatment/ pretreatment processes or to final treatment and disposal in a
subsurface soil disposal system. Various types of pretreatment may be used ahead of the aerobic units, including
septic tanks and trash traps.
The batch flow system collects and treats wastewater over
a period of time, then discharges the settled effluent at
the end of the cycle [8].
Aerobic units may be used by individual or clustered residences and establishments for treating wastewater before
either further treatment/pretreatment or final on-site subsurface treatment and disposal. These units are particularly applicable where enhanced pretreatment is
important, and where there is limited availability of land
suitable for final on-site disposal of wastewater effluent.
Because of their need for routine maintenance to ensure
proper operation and performance, aerobic units may be
well-suited for multiple-home or commercial applications, where economies of scale tend to reduce maintenance and/or repair costs per user. The lower organic and
suspended solids content of the effluent may allow a
reduction of land area requirements for subsurface disposal systems.
A properly functioning septic tank will remove approximately 75% of the suspended solids, oil, and grease from
effluent. Because the detention time in the tank is 24
hours or less, there is not a major kill of pathogenic bacteria. The bacteria will be removed in the absorption field
(drain field). However, there are soils and soil conditions
that prohibit the ability of a drain field to absorb effluent
from the septic tank.
Septic tanks are sized to retain the total volume of sewage
produced by a household in a 24-hour period. Normally
a 1,000-gallon tank is the minimum size to use. State or
local codes generally require larger tanks as the potential
occupancy of the home increases (e.g., 1,250 gallons for
four bedrooms) and may require two tanks in succession
when inadequate soils require alternative system installation. Figure 10.5 shows a typical septic tank.
Distribution boxes are not required by most on-site
plumbing codes or by the U.S. Environmental Protection
Agency. When used, distribution boxes provide a convenient inspection port. In addition, if a split system
absorption field is installed (two separate absorption
trench systems), the distribution box is a convenient place
to install a diversion valve for annually alternating absorption fields.
Figure 10.5. Septic Tank [9]
Absorption Field Site Evaluation
The absorption field has a variety of names, including
leach field, tile field, drain field, disposal field, and nitrification field. The effluent from the septic tank is directed
to the absorption field for final treatment. The suitability
of the soil, along with other factors noted below, determines the best way to properly treat and dispose of the
wastewater.
Most, but unfortunately not all, states require areas not
served by publicly owned sewers to be preapproved for
on-site wastewater disposal before home construction
through a permitting process. This process typically
requires a site evaluation by a local environmental health
specialist, soil scientist, or, in some cases, a private contractor. To assist in the site evaluation process, soil survey
maps from the local soil conservation service office may
be used to provide general information about soils in the
area.
The form shown in Figure 10.6 is typical of those used in
conducting a soil evaluation.
Sites for on-site wastewater disposal are first evaluated for
use with a conventional septic tank system. Evaluation
factors include site topography, landscape position, soil
texture, soil structure, internal drainage, depth to rock or
other restrictive horizons, and useable area. If the criteria
are met, a permit is issued to allow the installation of a
conventional septic tank system. Areas that do not meet
the criteria for a conventional system may meet lessrestrictive criteria for an alternative type of system.
Many sites are unsuitable for any type of on-site wastewater disposal system because of severe topographic limitations, poor soils, or other evaluation criteria. Such sites
10-5Chapter 10: On-site Wastewater TreatmentHealthy Housing Reference Manual
should not be used for on-site wastewater disposal
because of the high likelihood of system failure.
Some states and localities may require a percolation test
as part of the site evaluation process. As a primary
evaluation method, percolation tests are a poor indicator
of the ability of a soil to treat and move wastewater
throughout the year. However, information obtained by
percolation tests may be useful when used in conjunction
with a comprehensive soil analysis.
Absorption Field Trench
A conventional absorption field trench (Figure 10.7), also
known as a rock lateral system, is the most common
system used on level land or land with moderate slopes
with adequate soil depth above the water table or other
restrictive horizons. The effluent from the septic tank
flows through solid piping to a distribution box or, in many
cases, straight to an absorption field. With the conventional
system and most alternative systems, the effluent flows
through perforated pipes into gravel-filled trenches and
subsequently seeps through the gravel into the soil.
The local regulatory agency should be consulted about
the acceptable depth of the absorption field trench. Some
states require as much as 4 feet of separation beneath the
bottom of the trench and the groundwater. The depth of
absorption field trenches should be at least 18 inches, and
ideally no deeper than 24 inches. The absorption field
pipe should be laid flat with no slope. There should be a
Figure 10.6. On-site Sewage Disposal System Site Evaluation Form
Figure 10.7. Cross-section of an Absorption Field [10]
minimum of 12 to 18 inches of acceptable soil below the
bottom of the trench to any bedrock, water table, or
restrictive horizon. The length of the trench should not
exceed 100 feet for systems using a distribution box.
Serpentine systems may be several hundred feet long and
should be filled with crushed or fragmented clean rock or
gravel in the bottom 6 inches of the trench. Perforated
4-inch-diameter pipe is laid on top of the gravel then
covered with an additional 2 inches of rock and leveled for
a total of 12 inches. A geotextile material or a biodegradable
material such as straw should be placed over the gravel
before backfilling the trench to prevent soil from clogging
the spaces between the rocks.
One or more monitoring ports should be installed in the
absorption area extending to the bottom of the gravel to
allow measurement of the actual liquid depth in the
gravel. This is essential for subsequent testing of the
adequacy of the system.
Healthy Housing Reference Manual10-6 Chapter 10: On-site Wastewater Treatment
As a general rule, using longer and narrower trenches to
meet square footage requirements produces a better working and longer lasting ground absorption sewage disposal
system. Studies have shown that as septic systems age, the
majority of effluent absorption by the soil is provided by
lateral movement through the trench sidewalls. Longer
and narrower trenches (such as 400 feet long by 2 feet
wide instead of 200 feet by 4 feet to obtain 800 square
feet) greatly increase the sidewall area of the system for
lateral movement of wastewater.
Alternative Septic Tank Systems
As the cost of land for home building increases and the
availability of land decreases, land that was once considered unsuitable is being developed. This land often has
poor soil and drainage properties. Such sites require a
considerable amount of engineering skill to design an
acceptable wastewater disposal system. In many cases,
sites are not acceptable for seepage systems within a reasonable cost. These systems are primarily regulated by
state and local government and, before use, approval must
be obtained from the appropriate regulatory agencies.
Even if a site is approved in one state or county jurisdiction, a similar site may not be approved in another.
The primary difficulty with septic tank systems is treating
effluent in slowly permeable or marginal soils. Low-wateruse devices, when installed, may make it possible to use a
small percentage of septic tank systems in marginal soil.
However, low-water-use devices are usually required as
part of a larger effort to develop a usable alternative sewage disposal system. Alternative sewage disposal methods
that can be used if regular subsurface disposal is not
appropriate are numerous [11]. Some of the more common alternative systems are described below.
Advantages Disadvantages
May be used in areas with high groundwater, bedrock,
or restrictive clay soil near the surface
Must be installed on relatively level lots
Space efficient compared to conventional rock
lateral systems
Periodic flushing of the distribution network is required
Allows home building in areas unsuitable for below
grade systems
System may be expensive
Water softener wastes, common household chemicals,
and detergents are not harmful to this system
System may be difficult to design
Regular inspection of the pumps and controls necessary to
maintain the system in proper working condition
Table 10.1. Mound System Advantages and Disadvantages
Mound Systems
A mound system (Table 10.1) is elevated above the natural soil surface to achieve the desired vertical separation
from a water table or impervious material. The elevation
is accomplished by placing sand fill material on top of the
best native soil stratum. At least 1 foot of naturally occurring soil is necessary for a mound system to function
properly. Minimizing water usage in the home also is critical to prevent effluent from weeping through the sides of
the mound (Figure 10.8).
When a mound system is constructed, the septic tank
usually receives wastewater from the house by gravity
flow. A lift station is located in the second compartment
or in a separate tank to pump the effluent up to the distribution piping in the mound. Floats in the lift station
control the size of the pumped effluent dose. An alarm
should be installed to alert the homeowner of pump failure so that repairs can be made before the pump tank
overfills.
Low-Pressure Pipe Systems
Low-pressure pipe (LPP) systems may also be used where
the soil profile is shallow. These systems are similar to
mounds except that they use naturally occurring soil as it
exists on-site instead of elevating the disposal field with
soil fill material. LPP systems are installed with a trenching machine at depths of 12 to 18 inches. The LPP system consists of a septic tank, high-water alarm, pumping
tank, supply line, manifold, lateral line, and submersible
effluent pump (Figure 10.9).
When septic tank effluent rises to the level of the pump
control in the pumping tank, the pump turns on, and
effluent moves through the supply line and distribution
10-7Chapter 10: On-site Wastewater TreatmentHealthy Housing Reference Manual
laterals. The laterals contain small holes and are typically
placed 3 to 8 feet apart. From the trenches, the effluent
moves into the soil where it is treated. The pump turns
off when the effluent falls to the lower control. Dosing
takes place one to two times daily, depending on the
amount of effluent generated. Pump malfunctions set off
an alarm to alert the homeowner. The time between doses
allows the effluent to be absorbed into the soil and also
allows oxygen to reenter the soil to break down solids that
may be left behind. If the pump malfunctions, an alarm
notifies the homeowner to contact a qualified septic system contractor. The pump must be repaired or replaced
quickly to prevent the pump tank from overflowing.
Table 10.2 shows the advantages and disadvantages of
LPP systems.
Figure 10.9. Low Pressure On-site System [12]
Advantages Disadvantages
Space requirements are nearly half those of a conventional
septic tank system
Some low-pressure pipe systems may gradually accumulate
solids at the dead-ends of the lateral lines; therefore,
maintenance is required
Can be installed on irregular lot shapes and sizes Electric components are necessary
Can be installed at shallower depths and requires less topsoil cover
Design and installation may be difficult; installers with
experience with such systems should be sought
Provides alternating dosing and resting cycles
Installation sites are left in their natural condition
Table 10.2. Low-pressure Pipe Systems Advantages and Disadvantages
Figure 10.8. Mound System Cutaway [3]
Plant-rock Filter Systems (Constructed Wetlands)
Considered experimental in some states, plant-rock filter
systems are being used with great success in Kentucky,
Louisiana, and Michigan. Plant-rock filters generally consist of a septic tank (two-compartment), a rock filter, and
a small overflow lateral (absorption) field. Overflow from
the septic tank is directed into the rock filter. The rock
filter is a long narrow trench (3 to 5 feet wide and 60 to
100 feet long) lined with leak-proof polyvinyl chloride or
butylplastic to which rock is added. A 2- to 4-inch-diameter rock is used below the effluent flow line and larger
rock above (Figure 10.10).
Plant-rock filter systems are typically sized to allow 1.3
cubic feet of rock area per gallon of total daily waste flow.
A typical size for a three-bedroom house would be 468
square feet of interior area. Various width-to-length ratios
within the parameters listed above could be used to
obtain the necessary square footage. The trenches can
even be designed in an “L” shape to accommodate small
building lots.
Treatment begins in the septic tank. The partially treated
wastewater enters the lined plant-rock filter cell through
solid piping, where it is distributed across the cell. The
plants within the system introduce oxygen into the wasteHealthy Housing Reference Manual10-8 Chapter 10: On-site Wastewater Treatment
water through their roots. As the wastewater becomes
oxygenated, beneficial microorganisms and fungi thrive
on and around the roots, which leads to digestion of
organic matter. In addition, large amounts of water are
lost through evapotranspiration. The kinds of plants most
widely used in these systems include cattails, bulrush,
water lilies, many varieties of iris, and nutgrass. Winter
temperatures have little effect because the roots are doing
the work in these systems, and they stay alive during the
winter months. Discharge from wetlands systems may
require disinfection. The advantages and disadvantages of
the plant-rock filter system are shown in Table 10.3.
Maintaining On-site Wastewater
Treatment Systems
Do’s and don’ts inside the house:
• Do conserve water. Putting too much water into the
septic system can eventually lead to system failure.
Figure 10.10. Plant-rock Filter system [12]
Advantages Disadvantages
Approximately one-third the size of conventional septic
tank absorption field systems
May be slightly more costly to install
Disinfection required for effluent discharge
Can be placed on irregular or segmented lots May not find installers knowledgeable about the system
May be placed in areas with shallow water tables, high
bedrock, or restrictive horizons
Life span of the system is unknown because of its relative
newness
Relatively low maintenance Perception of being unsightly to some
Table 10.3. Plant-rock Filter System Advantages and Disadvantages
(Typical water use is about 60 gallons per day for
each person in the family.) The standard drain field is
designed for a capacity of 120 gallons per bedroom.
If near capacity, systems may not work. Water
conservation will extend the life of the system and
reduce the chances of system failure.
• Do fix dripping faucets and leaking toilets.
• Do avoid long showers.
• Do use washing machines and dishwashers only for
full loads.
• Do not allow the water to run continually when
brushing teeth or while shaving.
• Do avoid disposing of the following items down the
sink drains or toilets: chemicals, sanitary napkins,
tissues, cigarette butts, grease, cooking oil, pesticides,
kitty litter, coffee grounds, disposable diapers,
stockings, or nylons.
• Do not install garbage disposals.
• Do not use septic tank additives or cleaners. They are
unnecessary and some of the chemicals can
contaminate the groundwater.
Do’s and don’ts for outside maintenance:
• Do maintain adequate vegetative cover over the
absorption field.
• Do not allow surface waters to flow over the tank
and drain field areas. (Diversion ditches or subsurface
tiles may be used to direct water away from system.)
• Do not allow heavy equipment, trucks, or
automobiles to drive across any part of the system.
• Do not dig into the absorption field or build
additions near the septic system or the repair area.
10-9Chapter 10: On-site Wastewater TreatmentHealthy Housing Reference Manual
• Do make sure a concrete riser (or manhole) is
installed over the tank if not within 6 inches of the
surface, providing easy access for measuring and
pumping solids. (Note: All tanks should have two
manholes, one positioned over the inlet device and
one over the outlet device.)
There is no need to add any commercial substance to
“start” or clean a tank to keep it operating properly. They
may actually hinder the natural bacterial action that takes
place inside a septic tank. The fecal material, cereal grain,
salt, baking soda, vegetable oil, detergents, and vitamin
supplements that routinely make their way from the
house to the tank are far superior to any additive.
Symptoms of Septic System Problems
These symptoms can mean you have a serious septic system problem:
• Sewage backup in drains or toilets (often a black liquid
with a disagreeable odor).
• Slow flushing of toilets. Many of the drains will drain
much slower than usual, despite the use of plungers or
drain-cleaning products. This also can be the result of
a clogged plumbing vent or a nonvented fixture.
• Surface flow of wastewater. Sometimes liquid seeps
along the surface of the ground near your septic
system. It may or may not have much of an odor and
will range from very clear to black in color.
• Lush green grass over the absorption field, even during
dry weather. Often, this indicates that an excessive
amount of liquid from the system is moving up
through the soil, instead of down, as it should.
Although some upward movement of liquid from the
absorption field is good, too much could indicate
major problems.
• The presence of nitrates or bacteria in the drinking
water well indicates that liquid from the system may
be flowing into the well through the ground or over
the surface. Water tests available from the local health
department will indicate whether this is a problem.
• Buildup of aquatic weeds or algae in lakes or ponds
adjacent to your home. This may indicate that
nutrient-rich septic system waste is leaching into the
surface water, which may lead to both inconvenience
and possible health problems.
• Unpleasant odors around the house. Often, an
improperly vented plumbing system or a failing septic
system causes a buildup of disagreeable odors.
Table 10.4 is a guide to troubleshooting septic tank
problems.
Septic Tank Inspection
The first priority in the inspection process is the safety of
the homeowner, neighbors, workers, and anyone else for
which the process could create a hazard.
• Do not enter septic tanks or cesspools.
• Do not work alone on these tanks.
• Do not bend or lean over septic tanks or cesspools.
• Note and take appropriate action regarding unsafe
tank covers.
• Note unsanitary conditions or maintenance needs
(sewage backups, odor, seepage).
• Do not bring sewage-contaminated clothing into the
home.
• Have current tetanus inoculations if working in septic
tank inspection.
Methane and hydrogen sulfide gases are produced in a
septic tank. They are both toxic and explosive. Hydrogen
sulfide gas is quite deceptive. It can have a very strong
odor one moment, but after exposure, the odor may not
be noticed.
Inspection Process
As sewage enters a septic tank, the rate of flow is reduced
and heavy solids settle, forming sludge. Grease and other
light solids rise to the surface, forming a scum. The
sludge and scum (Figure 10.11) are retained and break
down while the clarified effluent (liquid) is discharged to
the absorption field.
Sludge eventually accumulates in the bottom of all septic
tanks. The buildup is slower in warm climates than in
colder climates. The only way to determine the sludge
depth is to measure the sludge with a probe inserted through
an inspection port in the tank’s lid. Do not put this job off until
the tank fills and the toilet overflows. If this happens, damage
to the absorption field could occur and be expensive to repair.
Scum Measurement
The floating scum thickness can be measured with a
probe. The scum thickness and the vertical distance from
the bottom of the scum to the bottom of the inlet can
also be measured. If the bottom of the scum gets within 3
inches of the outlet, scum and grease can enter the
absorption field. If grease gets into the absorption field,
percolation is impaired and the field can fail. If the scum
Healthy Housing Reference Manual10-10 Chapter 10: On-site Wastewater Treatment
Problem Possible Cause(s) Remedies
Wastewater backs up into the building
or plumbing fixtures sluggish or do
not drain well.
Excess water entering the septic tank
system, plumbing installed improperly,
roots clogging the system, plumbing
lines blocked, pump failure, absorption
field damaged or crushed by vehicular
traffic.
Fix leaks, stop using garbage disposal,
clean septic tank and inspect pumps,
replace broken pipes, seal pipe connections, avoid planting willow trees
close to system lines. Do not allow
vehicles to drive over or park over
lines. Contact local health department
for guidance.
Wastewater surfaces in the yard. Excess water entering the septic tank
system, system blockage, improper
system elevations, undersized soil
treatment system, pump failure,
absorption field damaged or crushed
by vehicular traffic.
Fix leaks, clean septic tank and check
pumps, make sure distribu tion box is
free of debris and functioning properly, fence off area until problem is
fixed, call in experts. Contact local
health department for guidance.
Sewage odors indoors. Sewage surfacing in yard, improper
plumbing, sewage backing up in the
building, trap under sink dried out,
roof vent pipe frozen shut.
Repair plumbing, clean septic tank
and check pumps, replace water in
drain pipes, thaw vent pipe. Contact
local health department for guidance.
Sewage odors outdoors. Source other than owner’s system,
sewage surfacing in yard, manhole or
inspection pipes damaged or partially
removed, downdraft from vent pipes
on roof.
Clean tank and check pumps, replace
damaged inspection port covers,
replace or repair absorption field.
Contact local health department for
guidance.
Contaminated drinking water or surface water.
System too close to a well, water
table, or fractured bedrock; cesspool
or dry well being used; improper well
construction; broken water supply or
wastewater lines. Improperly located
wells must be sealed in strict accordance with state and local codes.
Abandon well and locate a new one far
and upslope from the septic system,
fix all broken lines, stop using cesspool or drywell. Contact local health
department for guidance.
Distribution pipes and soil treatment
system freeze in winter.
Improper construction, check valve in
lift station not working, heavy equipment traffic compacting soil in area,
low flow rate, lack of use.
Examine check valve, keep heavy
equipment such as cars off area,
increase water usage, have friend run
water while away on vaca tion, operate
septic tank as a holding tank, do not
use anti freeze. Contact local health
department for guidance.
Table 10.4. Septic Tank System Troubleshooting
Figure 10.11. Sludge and Scum in Multicompartment Septic Tank [13]
is near the bottom of the tee, the
septic tank needs to be cleaned
out. The scum thickness can best
be measured through the large
inspection port. Scum should
never be closer than 3 inches to
the bottom of the baffle. The scum
thickness is observed by breaking
through it with a probe, usually a
pole.
10-11Chapter 10: On-site Wastewater TreatmentHealthy Housing Reference Manual
Sludge Measurement
To measure sludge, make a sludge-measuring stick using a
long pole with at least 3 feet of white cloth (e.g., an old
towel) on the end. Lower the measuring stick into the
tank, behind the outlet baffle to avoid scum particles,
until it touches the tank bottom. It is best to pump each
tank every 2 to 3 years. Annual checking of sludge level is
recommended. The sludge level must never be allowed to
rise within 6 inches of the bottom of the outlet baffle. In
two-compartment tanks, be sure to check both compartments. When a septic tank is pumped, there is no need to
deliberately leave any residual solids. Enough will remain
after pumping to restart the biologic processes.
References
1. University of California Cooperative Extension, Calaveras
County. Septic tanks: the real poop. San Andreas, CA:
University of California Cooperative Extension, Calaveras
County; no date. Available from URL: http://cecalaveras.
ucdavis.edu/realp.htm.
2. University of Nebraska-Lincoln. Residential on-site
wastewater treatment: septic system and drain field
maintenance. Lincoln, NE: University of
Nebraska-Lincoln; 2000. Available from URL: http://
ianrpubs.unl.edu/wastemgt/g1424.htm.
3. Rosenberg CE. The cholera years. Chicago: The University
of Chicago Press; 1962.
4. Salvato J, Nemerow NL, Agardy FJ, editors.
Environmental engineering. 5th ed. New York: John Wiley
and Sons; 2003.
5. Advanced Composting Systems. Phoenix composting
toilet system. Whitefish, MT: Advanced Composting
Systems; no date. Available from URL: http://www.
compostingtoilet.com.
6. BioLet USA, Inc. Composting toilets. Newcomerstown,
OH: BioLet USA, Inc.; no date. Available from URL:
http://www.biolet.com.
7. Mankl K, Slater B. Septic system maintenance. Columbus,
OH: The Ohio State University Extension; no date.
Available from URL: http://ohioline.osu.edu/
aex-fact/0740.html.
8. Hutzler NJ, Waldorf LE, Fancy J. Aerated tanks (aerobic
units). In: Performance of aerobic treatment units.
Madison, WI: University of Wisconsin - Madison; no
date. Available from URL: http://www.ci.austin.tx.us/wri/
treat5.htm.
9. Center for Disease Control. Basic housing inspection.
Atlanta: US Department of Health and Human Services;
1976.
10. Purdue Research Foundation. Environmental education
software series. West Lafayette, IN: Purdue Research
Foundation; 1989. Available from URL: http://
www. inspect-ny.com/septic/trench.gif.
11. North Carolina Cooperative Extension Service. On-site
wastewater treatment websites. Jacksonville, NC: North
Carolina Cooperative Extension Service; 2002. Available
from URL: http://www.ces.ncsu.edu/onslow/staff/
drashash/enved/sepsites.html.
12. Clay Township Regional Waste District. Septic systems.
Indianapolis: Clay Township Regional Waste District;
2004. Available from URL: http://www.ctrwd.org/septics.
htm.
13. Jackson Purchase Resource Conservation and
Development Foundation, Inc. Septic systems: an
overview. Cynthiana, KY: Jackson Purchase Resource
Conservation and Development Foundation, Inc.; no
date. Available from URL: http://www.jpf.org/
LRV/ septic.htm.
Additional Sources of Information
Agency for Toxic Substances and Disease Registry. Science
page, Office of the Associate Administrator for Science.
Atlanta: US Department of Health and Human Services;
no date. Available from URL: http://www.atsdr.cdc.gov/
science/.
American Society of Civil Engineers. Available from
URL: http://www.asce.org.
Burks BD, Minnis MM. Onsite wastewater treatment
systems. Madison, WI: Hogarth House, Ltd.; 1994.
Textbook and reference manual on all aspects of on-site
treatment.
International Code Council. International private sewage
disposal code, 2000. Falls Church, VA: International
Code Council; 2000.
National Onsite Wastewater Recycling Association
(NOWRA). Available from URL: http://www.nowra.org
or 1-800-966-2942.
National Small Flows Clearinghouse. Available from
URL: http://www.nesc.wvu.edu/nsfc/nsfc_index.htm or
1-800-624-8301.
US Army Corps of Engineers. Available from URL:
http://www.usace.army.mil.
Healthy Housing Reference Manual10-12 Chapter 10: On-site Wastewater Treatment
11-1Chapter 11: ElectricityHealthy Housing Reference Manual
'“To electrize plus or minus, no more needs to be known
than this, that the parts of the tube or sphere that are
rubbed, do, in the instant of the friction, attract the electrical
fire, and therefore take it from the thing rubbing; the same
parts immediately, as the friction upon them ceases, are
disposed to give the fire they have received to any body.”
Benjamin Franklin
Franklin’s Discovery of the Positive
and Negative States of Electricity, 1747
Introduction
Two basic codes concerned with residential wiring are
important to the housing inspector. The first is the local
electrical code. The purpose of this code is to safeguard
persons as well as buildings and their contents from hazards arising from the use of electricity for light, heat, and
power. The electrical code contains basic minimum provisions considered necessary for safety. Compliance with
this code and proper maintenance will result in an installation essentially free from hazards, but not necessarily
efficient, convenient, or adequate for good service or
future expansion.
Most local electrical codes are modeled after the National
Electrical Code, published by the National Fire
Protection Association (NFPA). Reference to the “code”
in the remainder of this chapter will be to the National
Electrical Code, unless specified otherwise [1].
An electrical installation that was safe and adequate under
the provisions of the electrical code at the time of installaChapter 11: Electricity
Ampere— The unit for measuring intensity of flow of electricity. Its symbol is “I.”
Bonding— Applies inert material to metal surfaces to eliminate electrical potential between metal components and
prevent components and piping systems from having an elevated voltage potential.
Circuit— The flow of electricity through two or more wires from the supply source to one or more outlets and back
to the source.
Circuit breaker— A safety device used to break the flow of electricity by opening the circuit automatically in the
event of overloading or used to open or close the circuit manually.
Conductor— Any substance capable of conveying an electric current. In the home, copper wire is usually used.
• A bare conductor is one with no insulation or covering.
• A covered conductor is one covered with one or more layers of insulation.
Definitions of Terms Related to Electricity
tion is not necessarily safe and adequate today. An example would be the grounding of a home electrical system.
In the past, electrical systems could be grounded to the
home’s plumbing system. Today, many plumbing systems
are no longer constructed of conductive material, but are
made of plastic or polyvinyl chloride-based materials.
Today, the recommendations for grounding a home electrical system are to use two 8-foot by 5/8-inch copper
ground rods. These must be spaced 6 feet apart and be
connected by a continuous (unbroken) piece of copper
wire (the size of this wire corresponds to the size of the
system main). It is also highly recommended that the
system be grounded to the incoming water line if it is
conductive or to the nearest conductive cold water supply line. Hazards often occur because of overloading wiring systems or usage not in conformity with the code.
This occurs because initial wiring did not provide for
increases in the use of electricity. For this reason, it is recommended that initial installations be adequate and that
reasonable provisions for system changes be made for
further increases in the use of electricity.
The other code that contains electrical provisions is the
local housing code. It establishes minimum standards for
artificial and natural lighting and ventilation, specifies
the minimum number of electric outlets and lighting fixtures per room, and prohibits temporary wiring except
under certain circumstances. In addition, the housing
code usually requires that all components of an electrical
system be installed and maintained in a safe condition to
prevent fire or electric shock.
Healthy Housing Reference Manual11-2 Chapter 11: Electricity
Flow of Electric Current
Electricity is usually created by a generator that converts
mechanical energy into electrical energy. The electricity
may be the result of water, steam, or wind powering or
turning a generator. The electricity is then run through a
transformer, where voltage is increased to several hundred
thousand volts and, in some instances, to a million or
more volts. This high voltage is necessary to increase the
efficiency of power transmission over long distances.
Conductor gauge— A numeric system used to label electric conductor sizes, given in American Wire Gauge (AWG). The
larger the AWG number, the smaller the wire size.
Current— The flow of electricity through a circuit.
• Alternating current is an electric current that reverses its direction of flow at regular intervals. For example, it would
alternate 60 times every second in a 60-cycle system. This type of power is commonly found in homes.
• Direct current is an electric current flowing in one direction. This type of current is not commonly found in today’s homes.
Electricity— Energy that can be used to run household appliances; it can produce light and heat, shocks, and numerous other
effects.
Fuse— A safety device that cuts off the flow of electricity when the current flowing through the fuse exceeds its rated capacity.
Ground— To connect with the earth, as to ground an electric wire directly to the earth or indirectly through a water pipe or
some other conductor. Usually, a green-colored wire is used for grounding the whole electrical system to the earth. A copper
wire is usually used to ground individual electrical components of the whole system. (The home inspector should never assume that insulation color wiring codes have been used appropriately.)
Ground fault circuit interrupter (GFCI)— A device intended to protect people from electric shock. It de-energizes a circuit
or portion of a circuit within an established very brief period of time when a current to ground exceeds some predetermined
value (less than that required to operate the over-current protected device of the supply circuit).
Hot wires— Those that carry the electric current or power to the load; they are usually black or red.
Insulator— A material that will not permit the passage of electricity.
Kilowatt-hour (KWH)— The amount of energy supplied by one kilowatt (1,000 watts) for 1 hour (3,600 seconds), equal to
3,600,000 joule. Electric bills are usually figured by the number of KWHs consumed.
Neutral wire— The third wire in a three-wire distribution circuit; it is usually white or light gray and is connected to the ground.
Resistance— A measure of the difficulty of electric current to pass through a given material; its unit is the ohm.
Service— The conductor and equipment for delivering energy from the electricity supply system to the wiring system of the
premises.
Service drop— The overhead service connectors from the last pole or other aerial support to and including the splices, if any,
connecting to the service entrance conductors at the building or other structure.
Service panel— Main panel or cabinet through which electricity is brought to the building and distributed. It contains the
main disconnect switch and fuses or circuit breakers.
Short circuit— A break in the flow of electricity through a circuit due to the load caused by improper connection between
hot and neutral wires.
Volt— The unit for measuring electrical pressure of force, which is known as electromotive force. Its symbol is “E.”
Voltage drop— A voltage loss when wires carry current. The longer the cord, the greater the voltage drop.
Watt— The unit of electric power. Volts times amperes = watts.
Definitions of Terms Related to Electricity
This high-transmission voltage is stepped down (reduced)
to normal 115/230-volt household current by a transformer
located near the point of use (residence). The electricity is
then transmitted to the house by a series of wires called a
service drop. In areas where the electric wiring is underground,
the wires leading to the building are buried in the ground.
For electric current to flow, it must travel from a higher
to a lower potential voltage. In an electrical system, the
hot wires (black or red) are at a higher potential than are
the neutral or ground wire (white or green).
11-3Chapter 11: ElectricityHealthy Housing Reference Manual
Voltage is a measure of the force at which electricity is
delivered. It is similar to pressure in a water supply
system.
Current is measured in amperes and is the quantity of
flow of electricity. It is similar to measuring water in gallons per second. A watt is equal to volts times amperes. It
is a measure of how much power is flowing. Electricity is
sold in quantities of kilowatt-hours.
The earth, by virtue of moisture contained within the
soil, serves as a very effective conductor. Therefore, in
power transmission, instead of having both the hot and
neutral wires carried by the transmission poles, one lead
of the generator is connected to the ground, which serves
as a conductor (Figure 11.1). All electrical utility wires are
carried by the transmission towers and are considered hot
or charged. At the house, or point where the electricity is
to be used, the circuit is completed by another connection to ground.
The electric power utility provides a ground somewhere
in its local distribution system; therefore, there is a
ground wire in addition to the hot wires within the service drop. In Figure 11.1 this ground can be seen at the
power pole that contains the step-down transformer.
In addition to the ground connection provided by the
electric utility, every building is required to have an independent ground called a system ground. The system
ground is a connection to ground from one of the current-carrying conductors of the electrical system. System
grounding, applied to limit overvoltages in the event of a
fault, provides personnel safety, provides a positive means
of detecting and isolating ground faults, and improves
service reliability. Therefore, the system ground’s main
purpose is to protect the electrical system itself and offers
limited protection to the user.
The system ground serves the same purpose as the power
company’s ground; however, it has a lower resistance
because it is closer to the building. The equipment
ground protects people from potential harm during the
Figure 11.1. Utility Overview [2] Figure 11.2. Entrance Head
use of certain electrical equipment. The system ground
should be a continuous wire of low resistance and of sufficient size to conduct current safely from lightning and
overloads.
Electric Service Entrance
Service Drop
To prevent accidental contact by people, the entrance head
(Figure 11.2) should be attached to the building at least
10 feet above ground. The conductor should clear all roofs
by at least 8 feet and residential driveways by 12 feet. For
public streets, alleys, roads, and driveways on other than
residential property, the clearance must be 18 feet.
The wires or conductor should be of sufficient size to
carry the load and not smaller than No. 8 copper wire or
equivalent.
For connecting wire from the entrance head to the service
drop wires, the code requires that the service entrance
conductors be installed either below the level of the service head or below the termination of the service entrance
cable sheath. Drip loops must be formed on individual
conductors. This will prevent water from entering the
electric service system. The wires that form the entrance
cable should extend 36 inches from the entrance head to
provide a sufficient length to connect service drop wires
to the building with insulators. The entrance cable may
be a special type of armored outdoor cable, or it may be
enclosed in a conduit. The electric power meter may be
located either inside or outside the building. In either
instance, the meter must be located before the main
power disconnect.
Healthy Housing Reference Manual11-4 Chapter 11: Electricity
Figure 11.3 shows an armored cable service entrance with
a fuse system. Newer construction will have circuit breakers, as shown in Figure 11.4. The armored cable is
anchored to the building with metal straps spaced every 4
feet. The cable is run down the wall and through a hole
drilled through the building. The cable is then connected
to the service panel, which should be located within 1
foot of where the cable enters the building. The ground
wire need not be insulated. This ground wire may be
either solid or stranded copper, or a material with an
equivalent resistance.
Figure 11.5 shows the use of thin-wall conduit in a service entrance.
Underground Service
When wires are run underground, they must be protected
from moisture and physical damage. The opening in the
Figure 11.5. Thin-wall Conduit [2]
Figure 11.3. Armored Cable Service Entrance [2]
Figure 11.4. Breakers [2]
building foundation where the underground service
enters the building must be moisture proof. Refer to local
codes for information about allowable materials for this
type of service entrance.
Electric Meter
The electric meter (Figure 11.6) may be located inside or
outside the building. The meter itself is weatherproof and
is plugged into a weatherproof socket. The electric power
company furnishes the meter; the socket may or may not
be furnished by the power company.
Grounding
The system ground consists of grounding the neutral
incoming wire and the neutral wire of the branch circuits.
The equipment ground consists of grounding the metal
parts of the service entrance, such as the service switch, as
well as the service entrance conduit, armor or cable.
11-5Chapter 11: ElectricityHealthy Housing Reference Manual
Poor grounding at any point can result in a person providing a more effective route to ground than the intended
ground, resulting in electrocution. This can occur from
damaged insulation allowing electricity to flow into the
case or cabinet of the appliance.
The system must be grounded by two 8 foot by 5/8-inch
copper ground rods of at least 8 feet in length driven into
the ground and connected by a continuous (unbroken)
piece of copper wire (the size of this wire corresponds to
the size of the system main). It is highly recommended
that the system also be grounded to the incoming water
line or nearest cold water supply line if it is metal.
The usual ground connection is to a conductive water
pipe of the city water system. The connection should be
made to the street side of the water meter, as shown in
Figure 11.7. If the water meter is located near the street
curb, then the ground connection should be made to the
cold water pipe as close as possible to where it enters the
building. It is not unusual for a water meter to be
removed from the building for service. If the ground connection is made at a point in the water piping system on
the building side of the water meter, the ground circuit
will be broken on removal of the meter. This broken
ground circuit is a shock hazard if both sides of the water
meter connections are touched simultaneously. Local or
state codes should be checked to determine compliance
with correct grounding protocols.
In increasing instances, the connections between the
water meters and pipes are electrically very poor. In this
case, if the ground connection is made on the building
side of the water meter, there may not be an effective
ground. To prevent the two aforementioned situations,
the code requires effective bonding by a properly sized
jumper-wire around any equipment that is likely to be
disconnected for repairs or replacement.
Often, the house ground will be disconnected. Therefore,
the housing inspector should always check the house
ground to see if it is properly connected.
Figure 11.6. Electric Meter Figure 11.7. Typical Service Entrance [2]
Figure 11.8 shows a typical grounding scheme at the service box of a residence. In this figure, only the grounded
neutral wires are shown. The neutral strap is a conductive
bare metal strip that is riveted directly to the service box.
This conductive strip forms a collective ground that joins
the ground wires from the service entrance, branch circuits, and house ground.
Follow these key grounding points:
• Use two metal rods driven 8 feet into the ground.
• Bond around water heaters and filters to assure
grounding.
• If water pipes are used, they must be supplemented
with a second ground.
• Ground rod must be driven to full depth.
• If ground rod resistance exceeds 25 ohms, install two
rods at a minimum of 6 feet apart.
• When properly grounded, the metal frame of a
building can be used as a ground point.
• Do not use underground gas lines as a ground.
• Provide external grounds to other systems such as
satellite, telephone, and other services to further
protect the electrical system from surges.
• If the water service pipes to the home are not metal or
if all of the service components in the home are not
metal, then the water system cannot play a role in
grounding.
Healthy Housing Reference Manual11-6 Chapter 11: Electricity
Bonding is necessary to provide a route for electricity to
flow around isolated elements of a piping system to
ensure electrical potential is minimized for both the protection of the system from corrosion and to protect individuals from electrical shock.
Two- or Three-wire Electric Services
One of the wires in every electrical service installation is
supposed to be grounded. This neutral wire should always
be white. The hot wires are usually black, red, or some
other color, but never white.
The potential difference or voltage between the hot wires
and the ground or neutral wire of a normal residential
electrical system is 115 volts. Thus, where there is a
two-wire installation (one hot and one neutral), only 115
volts are available.
When three wires are installed (two hot and one neutral),
either 115 or 230 volts are available. In a three-wire
system, the voltage between the neutral and either of the
hot wires is 115 volts; between the two hot wires, it is
230 (Figure 11.9). The major advantage of a three-wire
system is that it permits the operation of heavy electrical
equipment such as clothes dryers, cooking ranges, and air
conditioners, the majority of which require 230-volt
circuits. In addition, the three-wire system is split at the
service panel into two 115-volt systems to supply power
for small appliances and electric lights. The result is a
doubling of the number of circuits, and, possibly, a
corresponding increase in the number of branch circuits,
with a reduction in the probability of fire caused by
overloading electrical circuits if the electrical demands
exceed the capacity. Figure 11.9. Grounding [2]
Figure 11.8. Grounding Scheme [2]
Residential Wiring Adequacy
The use of electricity in the home has risen sharply since
the 1930s. Many homeowners have failed to repair or
improve their wiring to keep it safe and up to date. In the
1970s, the code recommended that the main distribution
panel in a home be a minimum of 100 amps. Because the
number of appliances that use electricity has continued to
grow, so has the size of recommended panels. For a normal house (2,500 to 3,500 square feet), a 200-amp panel
is recommended. The panel must be of the breaker type
with a main breaker for the entire system (Figure 11.4).
Fuse boxes are not recommended for new housing.
This type of service is sufficient in a one-family house or
dwelling unit to provide safe and adequate electricity for
the lighting, refrigerator, iron, and an 8,000-watt cooking
range, plus other appliances requiring a total of up to
10,000 watts.
Some older homes have a 60-ampere, three-wire service
(Figure 11.10). It is recommended that these homes be
rewired for at least the minimum of 200-amperes recommended in the code. The 60-amp service is safely capable
of supplying current for only lighting and portable appliances, such as a cooking range and regular dryer (4,500
watts), or an electric hot water heater (2,500 watts), and
cannot handle additional major appliances. Other older
homes today have only a 30-ampere, 115-volt, two-wire
service (Figure 11.11). This system can safely handle only
a limited amount of lighting, a few minor appliances, and
no major appliances. Therefore, this size service is substandard in terms of the modern household’s needs for
electricity. Furthermore, it is a fire hazard and a threat to
the safety of the home and the occupants.
Wire Sizes and Types
Aluminum wiring, used in some homes from the mid
1960s to the early 1970s, is a potential fire hazard [3].
According to the U.S. Consumer Product Safety
Commission (CPSC), fires and even deaths have been
caused by this hazard. Problems due to expansion can
cause overheating at connections between the wire and
devices (switches and outlets) or at splices. CPSC research
11-7Chapter 11: ElectricityHealthy Housing Reference Manual
shows that homes wired with aluminum wire manufactured before 1972 are 55 times more likely to have one or
more connections reach fire hazard conditions than are
homes wired with copper. Post-1972 aluminum wire is
also a concern. Introduction of aluminum wire alloys
around 1972 did not solve most of the connection failure
problems. Aluminum wiring is still permitted and used
for certain applications, including residential service
entrance wiring and single-purpose higher amperage circuits such as 240-volt air conditioning or electric range
circuits.
Reducing Risk
Only two remedies for aluminum wiring have been recommended by the CPSC: discontinued use of the aluminum circuit or the less costly option of adding copper
connecting “pigtail” wires between the aluminum wire
and the wired device (receptacle, switch, or other device).
The pigtail connection must be made using only a special
connector and special crimping tool licensed by the AMP
Corporation. Emergency temporary repairs necessary to
Figure 11.11. Two-wire Service [2]Figure 11.10. Three-wire Service [2]
keep an essential circuit in service might be possible following other procedures described by the CPSC, and in
accordance with local electrical codes [4,5].
Wire Sizes
Electric power actually flows along the surface of the
wire. It flows with relative ease (little resistance) in some
materials, such as copper and aluminum, and with a substantial amount of resistance in iron. If iron wire were
used, it would have to be 10 times as large as copper wire
to be as effective in conducting electricity. In fine electronics, gold is the preferred conductor because of the
resistance to corrosion and the very high conductivity.
Electricity is the movement of electrons from an area of
higher potential to one of lower potential. An analogy to
how electricity flows would be the flow of water along the
path of least resistance or down a hill. All it takes to create the potential for electricity is the collection of electrons and a pathway for them to flow to an area of lesser
concentration along a conductor. When a person walks
across a nylon carpet in times of low atmospheric humidity, his or her body will often collect electrons and serve
as a capacitor (a storage container for electrons). When
that person nears a grounding source, the electrons will
often jump from a finger to the ground, creating a spark
and small shock.
Healthy Housing Reference Manual11-8 Chapter 11: Electricity
A number preceded by the letters AWG (American Wire
Gauge) indicates copper wire sizes [6]. As the AWG
number of the wire becomes smaller, the size and current
capacity of the wire increases. AWG 14 is most
commonly found in older residential branch circuits.
AWG 14 wires should be used only in a branch circuit
with a 15-ampere capacity or no more than a 1,500-watt
demand. Wire sizes AWG 16, 18, and 20 are
progressively smaller than AWG 14 and are used for
extension wires or low-voltage systems. Wire of the
correct size must be used for two reasons: current capacity
and voltage drop or loss.
When current flows through a wire, it creates heat. The
greater the amount of flow, the greater the amount of
heat generated. (Doubling the amperes without changing
the wire size increases the amount of heat by four times.)
The heat is electric energy (electrons) that has been
converted into heat energy by the resistance of the wire.
The heat created by the coils in a toaster is an example of
designed resistance to create heat. Most heat developed by
an electrical conductor is wasted; therefore, the electric
energy used to generate it is also wasted.
If the amount of heat generated by the flow of current
through a wire becomes excessive, a fire may result.
Therefore, the code sets the maximum permissible
current that may flow through a certain type and size
wire. The blue box provides examples of current
capacities for copper wire of various sizes.
In addition to heat generation, there will be a reduction in
voltage as a result of attempting to force more current
through a wire than it is designed to carry. Certain
appliances, such as induction-type electric motors, may be
damaged if operated at too low a voltage.
Wire Types
All wires must be marked to indicate the maximum
working voltage, the proper type letter or letters for the
type wire specified in the code, the manufacturer’s name
or trademark, and the AWG size or circular-mil area
(Figure 11.12). A variety of wire types can be used for a
wide range of temperature and moisture conditions. The
code should be consulted to determine the proper wire
for specific conditions. Figure 11.12. Wire Markings [2]
Size wire (AWG) (larger wire, smaller number) #14 #12 #10 #8
Maximum capacity in amperes 15 20 30 40
Maximum Current Recommended for AWG Wire Size
Types of Cable
Nonmetallic sheathed cable consists of wires wrapped in
plastic and then a paper layer, followed by another spiral
layer of paper, and enclosed in a fabric braid, which is
treated with moisture- and fire-resistant compounds.
Figure 11.12 shows this type of cable, which often is
marketed under the name Romex. This type of cable can
be used only indoors and in permanently dry locations.
Romex-type wiring is normally used in residential
construction. However, when cost permits, it is recommended that a conduit-based system be used.
Armored cable is commonly known as BX or Flexsteel
trade names. Wires are wrapped in a tough paper and
covered with a strong spiral flexible steel armor. This
type of cable is shown in Figure 11.13 and may be used
only in permanently dry indoor locations. Armored cable
must be supported by a strap or staple every 6 feet and
within 24 inches of every switch or junction box, except
for concealed runs in old work where it is impossible to
mount straps.
Cables are also available with other outer coatings of metals, such as copper, bronze, and aluminum for use in a
variety of conditions.
Flexible Cords
CPSC estimates that about 4,000 injuries associated with
electric extension cords are treated in hospital emergency
rooms each year. About half of the injuries involve
fractures, lacerations, contusions, or sprains from people
tripping over extension cords. Thirteen percent of the
injuries involve children younger than 5 years of age;
electrical burns to the mouth account for half the injuries
to young children [7].
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CPSC also estimates that about 3,300 residential fires
originate in extension cords each year, killing 50 people
and injuring about 270 others [7]. The most frequent
causes of such fires are short circuits, overloading the system, and damage to or misuse of extension cords.
The Problem
Following are CPSC investigations of injuries that illustrate the major injury patterns associated with extension
cords: children putting extension cords in their mouths,
overloaded cords, worn or damaged cords, and tripping
over cords:
• A 15-month-old girl put an extension cord in her
mouth and suffered an electrical burn. She required
surgery.
• Two young children were injured in a fire caused by an
overloaded extension cord in their family’s home. A
lamp, TV set, and electric heater had been plugged
into a single, light-duty extension cord.
• A 65-year-old woman was treated for a fractured ankle
after tripping over an extension cord.
The Standards
The code says that many cord-connected appliances
should be equipped with polarized grounding plugs.
Polarized plugs can only be inserted one way into the
outlet because one blade is slightly wider than the other.
Polarization and grounding ensure that certain parts of
appliances that could have a higher risk of electric shock
when they become live are instead connected to the neutral, or grounded, side of the circuit. Such electrical products should only be used with polarized or grounded
extension cords.
Voluntary industry safety standards, including those of
Underwriter’s Laboratory (UL), now require that generaluse extension cords have safety closures, warning labels,
rating information about the electrical current, and other
features for the protection of children and other
consumers.
In addition, UL-listed extension cords now must be constructed with 16-gauge or larger wire or be equipped with
integral fuses. The 16-gauge wire is rated to carry 13
amperes (up to 1,560 watts), as compared with the forFigure 11.13. Armored Cable [2]
merly used 18-gauge cords that were rated for 10 amperes
(up to 1,200 watts).
Safety Suggestions
The following are CPSC recommendations [7] for
purchasing and safely using extension cords:
• Use extension cords only when necessary and only on
a temporary basis.
• Use polarized extension cords with polarize appliances.
• Make sure cords do not dangle from the counter or
tabletops where they can be pulled down or tripped
over.
• Replace cracked or worn extension cords with new
16-gauge cords that have the listing of a nationally
recognized testing laboratory, safety closures, and other
safety features.
• With cords lacking safety closures, cover any unused
outlets with electrical tape or with plastic caps to
prevent the chance of a child making contact with the
live circuit.
• Insert plugs fully so that no part of the prongs is
exposed when an extension cord is in use.
• When disconnecting cords, pull the plug rather than
the cord itself.
• Teach children not to play with plugs and outlets.
• Use only three-wire extension cords for appliances
with three-prong plugs. Never remove the third (round
or U-shaped) prong, which is a safety feature designed
to reduce the risk for shock and electrocution.
• In locations where furniture or beds may be pushed
against an extension cord where the cord joins the
plug, use a special angle extension cord specifically
designed for use in these instances.
• Check the plug and the body of the extension cord
while the cord is in use. Noticeable warming of these
plastic parts is expected when cords are being used at
their maximum rating. If the cord feels hot or if there
is a softening of the plastic, this is a warning that the
plug wires or connections are failing and that the
extension cord should be discarded and replaced.
• Never use an extension cord while it is coiled or
looped. Never cover any part of an extension cord with
newspapers, clothing, rugs, or any objects while the
cord is in use. Never place an extension cord where it
is likely to be damaged by heavy furniture or foot
traffic.
Healthy Housing Reference Manual11-10 Chapter 11: Electricity
• Do not use staples or nails to attach extension cords to
a baseboard or to another surface. This could damage
the cord and present a shock or fire hazard.
• Do not overload extension cords by plugging in
appliances that draw a total of more watts than the
rating of the cord.
• Use special heavy-duty extension cords for highwattage appliances such as air conditioners, portable
electric heaters, and freezers.
• When using outdoor tools and appliances, use only
extension cords labeled for outdoor use.
Wiring
Open Wiring
Open wiring is a wiring method using knobs, nonmetallic tubes, cleats, and flexible tubing for the protection and
support of insulated conductors in or on buildings and
not concealed by the structure. The term “open wiring”
does not mean exposed, bare wiring. In dry locations,
when not exposed to severe physical damage, conductors
may be separately encased in flexible tubing. Tubing
should be in continuous lengths not exceeding 15 feet
and secured to the surface by straps not more than 4½
feet apart. Tubing should be separated from other conductors by at least 2½ inches and should have a permanently maintained airspace between them and any and all
pipes they cross.
Concealed Knob and Tube Wiring
Concealed knob and tube wiring is a wiring method
using knobs, tubes, and flexible nonmetallic tubing for
the protection and support of insulated wires concealed
in hollow spaces of walls and ceilings of buildings. This
wiring method is similar to open wiring and, like open
wiring, is usually found only in older buildings.
Electric Service Panel
The service switch is a main switch that will disconnect
the entire electrical system at one time. The main fuses or
circuit breakers are usually located within the service
switch box. The branch circuit fuse or circuit breaker may
also be located within this box.
According to the code, the switch must be externally
operable. This condition is fulfilled if the switch can be
operated without the operator being exposed to electrically active parts. Figure 11.14 shows a 200-amp service
box. Figure 11.15 shows an external “hinged switch”
power shutoff installed on the outside of a home.
Figure 11.15. External Power Shutoff and Meter
Most of today’s older
homes do not have
hinged switches.
Instead, the main fuse
is mounted on a small
insulated block that
can be pulled out of
the switch. When this
block is removed, the
circuit is broken.
In some installations,
the service switch is a
“solid neutral” switch,
meaning that the
switch or a fuse does
not break the neutral wire in the switch.
When circuit breakers are used in homes instead of fuses,
main circuit breakers may or may not be required. If it
takes more than six movements of the hand to open all
the branch-circuit breakers, a main breaker, switch, or
fuse will be required ahead of the branch-circuit breakers.
Thus, a house with seven or more branch circuits requires
a separate disconnect means or a main circuit breaker
ahead of the branch-circuit breakers.
Over-current Devices
The amperage (current flow) in any wire is limited to the
maximum permitted by using an over-current device of a
size specified by the code. Four types of over-current
devices are common: circuit breakers, ground fault circuit
interrupters (GFCIs), arc fault circuit interrupters
(AFCIs), and fuses. The over-current device of a specific
size is specified by the code. The over-current device must
be rated at equal or lower capacity than the wire of the
circuit it protects.
Figure 11.14. 200-Amp Service Box
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Circuit Breakers (Fuseless Service Panels)
A circuit breaker looks something like an ordinary electric
light switch. Figure 11.14 shows the service box in a 200amp fuseless system. Figure 11.15 shows a service switch.
There is a handle that may be used to turn power on or
off. Inside is a simple mechanism that, in case of a circuit
overload, trips the switch and breaks the circuit. The circuit breaker may be reset by turning the switch to off and
then simply resetting the switch to the on position. A circuit breaker is capable of taking harmless short-period
overloads (such as the heavy initial current required in the
starting of a washing machine or air conditioner) without
tripping, but protects against prolonged overloads. After
the cause of trouble has been located and corrected,
power is easily restored. Fuseless service panels or breaker
boxes are usually broken up into the following circuits:
• A 100-ampere or larger main circuit breaker that
shuts off all power.
• A 40-ampere circuit for an appliance such as an
electric cooking range.
• A 30-ampere circuit for a clothes dryer, water heater,
heat pump, or central air conditioning.
• A 20-ampere circuit for small appliances and power
tools.
• A 15-ampere circuit for general-purpose lighting,
TVs, VCRs, computers, and vacuum cleaners.
• Space for new circuits to be added if needed for
future use.
Ground Fault Circuit Interrupters
Unlike circuit breakers and fuses, GFCIs are installed to
protect the user from electrocution. These devices provide
protection against electrical shock and electrocution from
ground faults or contact with live parts by a grounded
individual. They constantly monitor electrical currents
flowing into a product. If the electricity flowing through
the product differs even slightly from that returning, the
GFCI will quickly shut off the current. GFCIs detect
amounts of electricity much smaller than those required
for a fuse or circuit breaker to activate and shut off the
circuit. UL lists three types of GFCIs designed for home
use that are readily available and fairly inexpensive and
simple to install:
• Wall Receptacle GFCI— This type of GFCI (Figure
11.16) is used in place of a standard receptacle found
throughout the house. It fits into a standard outlet box
and protects against ground faults whenever an
electrical product is plugged into the outlet. If
strategically located, it will also
provide protection to
downstream receptacles.
• Circuit Breaker GFCI— In
homes equipped with circuit
breakers, this type of GFCI may
be installed in a panel box to
protect selected circuits. A circuit
breaker GFCI serves a dual
purpose: it shuts off electricity in
the event of a ground fault and
will also trip when a short circuit
or an overload occurs.
• Portable GFCI— A portable GFCI requires no special
knowledge or equipment to install. One type contains
the GFCI circuitry in a self-contained enclosure with
plug blades in the back and receptacle slots in the
front. It can be plugged into a receptacle, and the
electrical product plugged into the GFCI. Another
type of portable GFCI is an extension cord combined
with a GFCI. It adds flexibility in using receptacles
that are not protected by GFCIs.
Once a GFCI is installed, it must be checked monthly to
determine that it is operating properly. Pressing the test
button can check units; the GFCI should disconnect the
power to that outlet. Pressing the reset button reconnects
the power. If the GFCI does not disconnect the power,
have it checked by a qualified, certified electrician.
GFCIs should be installed on circuits in the following
areas: garages, bathrooms, kitchens, crawl spaces, unfinished basements, hot tubs and spas, pool electronics, and
exterior outlets. However, they are not required on single
outlets that serve major appliances.
Arc-fault Circuit Interrupters
Arc-fault circuit interrupters are new devices intended to
provide fire protection by opening the circuit if an arcing
fault is detected. An arcing fault is an electric spark or hot
plasma field that extends from the hot wire to a ground.
An arc is a luminous discharge of electricity across an
insulating medium or simply a spark across an air gap.
Arcs occur every day in homes. For example, an arc
occurs inside the switch when a light is turned on. Toy
racecars and trains create arcs. The motors inside hair
dyers and power drills have tiny arcs. All of these are controlled arcs. It is the uncontrolled or nondesigned arc that
is a serious fire hazard in the home. The arc-fault circuit
interrupter looks like the GFCI unit (Figure 11.17), but
it is not designed to protect against electric shock.
Figure 11.16. GFCI
Healthy Housing Reference Manual11-12 Chapter 11: Electricity
and the neutral wire is grounded the same as for a
two-wire system. Below each fuse is a terminal to which a
black or red wire is connected. The white or light gray
neutral wires are then connected to the neutral strip.
Each fuse indicates a separate circuit (Figure 11.18).
• Nontamperable fuses— All ordinary plug fuses have
the same diameter and physical appearance, regardless
of their current capacity, whereas nontamperable fuses
are sized by amperage load. Thus, with regular fuses, if
a circuit designed for a 15-ampere fuse is overloaded so
that the 15-ampere fuse blows out, nothing will
prevent a person from replacing the 15-ampere fuse
with a 20- or 30-ampere fuse, which may not blow
out. If a circuit wired with 14-gauge wire (current
capacity 15 amperes) is fused with a 20- or 30-ampere
fuse and an overload develops, more current than the
14-gauge wire is safely capable of carrying could pass
through the circuit. The result would be a heating of
the wire and potential fire.
• Type-S fuses— Type-S fuses have different lengths and
diameter threads for each amperage capacity. An
adapter is first inserted into the ordinary fuse holder,
which adapts the fuse holder for only one capacity
fuse. Once the adapter is inserted, it cannot be
removed.
• Cartridge fuses— A cartridge fuse protects an electric
circuit in the same manner as an ordinary plug fuse,
already described, protects an electric circuit. Cartridge
fuses are often used as main fuses.
Because most electrical wiring
in a home is hidden from view,
many arc faults go undetected
and continue arcing indefinitely. If left in this arcing
state, the potential for fire
increases. It is estimated that
about one third of fires are
caused by arcing faults. Normal
fuses and circuit breakers are not capable of detecting arc
faults and therefore will not open the circuit and stop the
flow of electricity.
Fused Ampere Service Panel (Fuse Box)
Fuse-type panel boxes are generally found in older homes.
They are as safe and adequate as a circuit breaker of equivalent capacity, provided fuses of the proper size are used.
A fuse, like a circuit breaker, is designed to protect a circuit against overloading and short circuits and does so in
two ways.
When a fuse is blown by a short circuit, the metal strip is
instantly heated to an extremely high temperature, and
this heat causes it to vaporize. A fuse blown by a short
circuit may be easily recognized because the window of
the fuse usually becomes discolored.
In a fuse blown by an overload, the metal strip is melted
at its weakest point, breaking the flow of current to the
load. In this case, the window of the fuse remains clear;
therefore, a blown fuse caused by an overload may also be
easily recognized.
Sometimes, although a fuse has not been blown, the bottom of the fuse may be severely discolored and pitted.
This indicates a loose connection because the fuse was
not screwed in properly.
It is critical to check that all fuses are properly rated for
the designed amperage. The placing of a fuse with a
higher amperage than recommended presents a significant
fire hazard.
Generally, all fused panel boxes are wired similarly for
two- and three-wire systems. In a two-wire-circuit panel
box, the black or red hot wire is connected to a terminal
of the main disconnect, and the white or light gray
neutral wire is connected to the neutral strip, which is then
grounded to the pipe on the street side of the water meter.
In a three-wire system, the black and red hot wires are
connected to separate terminals of the main disconnect,
Figure 11.18. Types of Fuses
Figure 11.17. Arc Interrupter
11-13Chapter 11: ElectricityHealthy Housing Reference Manual
Electric Circuits
An electric circuit in good repair carries electricity
through two or three wires from the source of supply to
an outlet and back to the source. A branch circuit is an
electric circuit that supplies current to a limited number
of outlets and fixtures. A residence generally has many
branch circuits. Each is protected against short circuits
and overloads by a 15- or 20-ampere fuse or circuit
breaker.
The number of outlets per branch circuit varies from
building to building. The code requires enough light circuits so that 3 watts of power will be available for each
square foot of floor area in a house. A circuit wired with
14-gauge wire and protected by a 15 ampere over-current
protection device provides 15×115 (1,725 watts); each
circuit is enough for 1,725 divided by 3 (575 square
feet). Note that 575 is a minimum figure; if future use is
considered, 500 or even 400 square feet per branch circuit should be used.
Special appliance circuits will provide electric power for
lighting, radio, TV, and small portable appliances.
However, the larger electric appliances usually found in
the kitchen consume more power and must have their
own special circuit.
Section 220-3b of the code requires two special circuits to
serve only appliance outlets in the kitchen, laundry, pantry, family room, dining room, and breakfast room. Both
circuits must be extended to the kitchen; either one or
both of these circuits may serve the other rooms. No lighting outlets may be connected to these circuits, and they
must be wired with 12-gauge wire and protected by a
20-ampere over-current device. Each circuit will have a
capacity of 20×115 (2,300 watts), which is not too much
when toasters often require more than 1,600 watts.
It is customary to provide a circuit for each of the following appliances: range, water heater, washing machine,
clothes dryer, garbage disposal, dishwasher, furnace, water
pump, air conditioner, heat pump, and air compressor.
These circuits may be either 115 volts or 230 volts,
depending on the particular appliance or motor installed.
Outlet Switches and Junction Boxes
The code requires that every switch, outlet, and joint in
wire or cable be housed in a box. Every fixture must be
mounted on a box. Most boxes are made of plastic or
metal with a galvanized coating. When a cable of any
style is used for wiring, the code requires that it be
securely anchored with a connector to each box it enters.
Grounding Outlets
An electrical appliance may appear to be in good repair,
and yet it might be a danger to the user. Older portable
electric drills consist of an electric motor inside a metal
casing. When the switch is depressed, the current flows to
the motor and the drill rotates. As a result of wear, however, the insulation on the wire inside the drill may deteriorate and allow the hot side of the power cord to come
in contact with the metal casing. This will not affect the
operation of the drill.
A person fully clothed using the drill in the living room,
which has a dry floor, will not receive a shock, even
though he or she is in contact with the electrified drill
case. The operator’s body is not grounded because of the
dry floor. If standing on a wet basement floor, the operator’s body might be grounded; and, when the electrified
drill case is touched, current will pass through the operator’s body.
To protect people from electrocution, the drill case is usually connected to the system ground by means of a wire
called an appliance ground. In this instance, as the drill is
plugged in, current will flow between the shorted hot
wire and the drill case and cause the over-current device
to break the circuit. Thus, the appliance ground has protected the human operator. Newer appliances and tools
are equipped with two-prong polarized plugs, as discussed
in the standards section of this manual.
The appliance ground (Figure 11.19) is the third wire
found on many appliances. The appliance ground will be
of no use unless the outlet into which the appliance is
plugged is grounded. Being in physical contact with a
ground outlet box grounds the outlet. Having a third
ground wire, or a grounded conduit, as part of the circuit
wiring grounds the outlet box.
All new buildings are required to have grounded outlets.
A two-lead circuit tester can be used to test the outlet.
The circuit tester lights when both of its leads are plugged
into the two elongated parallel openings of the outlet. In
addition, the tester lights when one lead is plugged into
the round third opening and the other is plugged into the
hot side of the outlet. Most problems can be resolved
using inexpensive testers resembling a plug with three
leads. These can be purchased in many stores and most
hardware stores for very reasonable prices.
If the conventional two-opening outlet is used, it may be
grounded if the screw that holds the outlet cover plate is
electrically connected to the third-wire ground. The tester
should light when one lead is in contact with a clean
Healthy Housing Reference Manual11-14 Chapter 11: Electricity
paint-free metal outlet cover plate screw and the hot side
of the outlet. If the tester does not light, the outlet is not
grounded. If a two-opening outlet is grounded, it may be
adapted for use by a three-wire appliance by using an
adapter. The loose-wire portion or screw tab of the
adapter should be secured behind the metal screw of the
outlet plate cover. Many appliances, such as electric shavers and some new hand tools, are double insulated and
are safe without having a third ground wire.
Polarized Plugs and Connectors
Plugs are polarized or unpolarized. Polarization helps
reduce the potential for shock. Consumers can easily
identify polarized plugs; one blade-the ground prong-is
wider than the other. Three-conductor plugs are
automatically polarized because they can only be inserted
one way. Polarized plugs are used to connect the
most-exposed part of an appliance to the ground wire so
that if you are touching a ground (such as a pipe,
bathtub, or faucet) and the exposed part of an appliance
(the case, the threaded part of a light bulb socket, etc.),
you will not get an electrical shock. Many appliances,
such as electric drills, are doubly insulated so the
probability of any exposed part of the appliance being
connected, by a short or other problem in the appliance,
to either wire is very small. Such devices often use
unpolarized plugs where the two prongs of the plug are
identical.
Common Electrical Violations
The most obvious things that a housing inspector must
check are the power supply; the type, location, and condition of the wiring; and the number and conditions of
wall outlets or ceiling fixtures required by the local code.
In making an investigation, the following considerations
will serve as useful guides.
• Power supply— Where is it, is it grounded properly,
and is it at least of the minimum capacity required to
supply current safely for lighting and the major and
minor appliances in the dwelling?
• Panel box covers or doors— These should be
accessible only from the front and should be sealed in
such a way that they can be operated safely without
the danger of contact with live or exposed parts of the
wiring system.
• Switch, outlets, and junction boxes— These also
must be covered to protect against danger of electric
shock.
• Frayed or bare wires— These are usually the result of
long use and drying out and cracking of the
insulation, which leave the wires exposed, or of
constant friction and rough handling of the wire,
which cause it to fray or become bare. Wiring in this
condition constitutes a safety hazard. Correction of
such defects should be ordered immediately.
• Electric cords under rugs or other floor coverings—
Putting electric cords in locations such as these is
prohibited because of the potential fire hazard caused
by continuing contact over a period of time between
these heat-bearing cords and the flammable floor
coverings. Direct the occupant to shift the cords to a
safe location, explain why, and make sure it is done
before you leave.
• Ground fault circuit interrupter— All bathroom,
kitchen, and workroom outlets-where shock hazard is
great-should have GFCI outlets. Check for lack of or
nonuse of GFCI outlets.
• Bathroom lighting— Bathrooms should include at
least one permanently installed ceiling or wall light
fixture with a wall switch and plate located and
maintained so that there is no danger of short
circuiting from use of other bathroom facilities or
splashing water. Fixture or cover plates should be
insulated or grounded.
Figure 11.19. Appliance Ground and Grounded Plug
11-15Chapter 11: ElectricityHealthy Housing Reference Manual
• Lighting of public hallways, stairways, landings,
and foyers— A common standard is sufficient lighting
to illuminate 10 foot-candles on every part of these
areas at all times. Sufficient lighting means that people
can clearly see their feet on all parts of the stairways
and halls. Public halls and stairways in structures
containing less than three dwelling units may be
supplied with conveniently located light switches
controlling an adequate lighting system that may be
turned on when needed, instead of full-time lighting.
• Habitable room lighting— The standard here may be
two floor convenience outlets (although floor outlets
are dangerous unless protected by proper dust and
water covers) or one convenience outlet and one wall
or ceiling electric light fixture. This number is an
absolute and often inadequate minimum, given the
contemporary widespread use of electricity in the
home. The minimum should be the number required
to provide adequate lighting and power to
accommodate lighting and appliances normally used
in each room.
• Octopus outlets or wiring— This term is applied to
outlets into which plugs have been inserted and are
being used to permit more than two lights or portable
appliances, such as a TV, lamp, or radio, to be
connected to the electrical system. The condition
occurs where the number of outlets is insufficient to
accommodate the normal use of the room. This
practice overloads the circuit and is a potential source
of fire.
• Outlet covers— Every outlet and receptacle must be
covered by a protective plate to prevent contact of its
wiring or terminals with the body, combustible
objects, or water.
Following are six situations that can cause danger and
should also be corrected.
Excessive or Faulty Fusing
The wire’s capacity must not be exceeded by the fuse or
circuit breaker capacity or be left unprotected by faulty
fusing or circuit breakers. Fuses and circuit breakers are
safety devices designed to “blow” to protect against
overloading the electrical system or one or more of its
circuits. Pennies under fuses are there to bypass the fuse.
These are illegal and must be removed. Overfusing is
done for the same reason. The latter can be prevented by
installing modern fusestats, which prevent use of any fuse of a
higher amperage than can be handled by the circuit it serves.
Cords Run Through Walls or Doorways and Hanging
Cords or Wires
This makeshift installation often is the work of an
unqualified handyman or do-it-yourself occupant. The
inspector should check the local electrical code to determine the policy regarding this type of installation.
Temporary Wiring
Temporary wiring should not be allowed, with the
exception of extension cords that go directly from portable
lights and electric fixtures to convenience outlets.
Excessively Long Extension Cords
City code standards often limit the length of loose cords
or extension lines to a maximum of 8 feet. This is necessary because cords that are too long will overheat if overloaded or if a short circuit develops and, thus, create a
fire hazard. This requirement does not apply to specially
designed extension cords for operating portable tools and
trouble lights.
Dead or Dummy Outlets
These are sometimes installed to deceive the housing
inspector. All outlets must be tested or the occupants
questioned to see if these are live and functioning
properly. A dead outlet cannot be counted to determine
compliance with the code.
Aluminum Wiring Inside the Home
Although aluminum is an excellent conductor, it tends to
oxidize on the conducting surface. The nonconductive
oxidized face of the conductor will arc from the remaining conductive surfaces, and this arc can result in fire.
Inspection Steps
The basic tools required by a housing inspector for making an electrical inspection are fuse and circuit testers and
a flashlight. The first thing to remember is that you are in
a strange house, and the layout is unfamiliar to you. The
second thing to remember is that you are dealing with
electricity-take no chances. Go to the site of the ground,
usually at the water meter, and check the ground. It
should connect to the water line on the street side of the
water meter or be equipped with a jumper wire. Do not
touch any box or wire until you are sure of the ground.
Go to the main fuse box or circuit breaker box and check
all fuses and breakers for operational integrity (proper
amperage range; functional). Note the condition of the
wiring and of the box itself and check whether it is overfused. Examine all wiring in the basement. Make sure
you are standing in a dry spot (concrete poses a particular
Healthy Housing Reference Manual11-16 Chapter 11: Electricity
problem because you cannot determine its water content
from visual examination) before touching any electrical
device. Standing on a dry piece of wood is far safer than
standing on concrete. Do not disassemble the fuse box,
circuit breaker, or other devices. Decisions must be made
on what you see. If in doubt, consult your supervisor.
Note whether any fuse boxes, circuit breakers, or junction
boxes are uncovered. Examine all wiring for frayed or
bare spots; improper splicing; or rotted, worn, or inadequate insulation. Avoid all careless touching; when in
doubt— DON’T! If you see bare wires, have the owner
call an electrician. Look for wires or cords in use in the
basement. Be certain all switch boxes and outlets are in a
tight, sound condition. Make sure that the emergency
switch for an oil burner is at the top of the basement
stairs, not on top of the unit.
Bathrooms, kitchens, and utility rooms-where electric
shock hazard is great-should have GFCI outlets.
While inspecting the bathroom, also check for dangerous
items, such as radios that are not made for bathroom use
or portable electric heaters. Have inappropriate items
removed immediately. Such items have killed thousands
of people who touched them after getting out of the
bathtub or shower while still wet or because the appliance
fell into water the person had contact with.
Electric washer and dryer combinations should have a
240-volt circuit, 30-ampere service connected to a
separate fuse or circuit breaker. Washer and dryer combinations and other portable appliances should be served
by sufficiently heavy electrical service. If either of these
special lines is not available under the above-stated conditions, consult your supervisor.
An electric range needs a 50-ampere, 240-volt circuit. A
dishwasher needs a 20-ampere, 120-volt circuit. A
separate three-wire circuit must be installed for an electric
water heater. Continue your inspection systematically
through the house.
To sum up, the housing inspector investigates specified
electrical elements in a house to detect any obvious evidence of an insufficient power supply, to ensure the availability of adequate and safe lighting and electrical
facilities, and to discover and correct any obvious hazard.
Because electricity is a technical, complicated field, the
housing inspector, when in doubt, should consult his or
her supervisor. The inspector cannot, however, close the
case until appropriate corrective action has been taken on
all such referrals.
References
1. National Fire Protection Association. National electrical
code handbook 2005. Florence, KY: Thomson Delmar
Learning; 2005.
2. Center for Disease Control. Basic housing inspection.
Atlanta: US Department of Health and Human Services;
1976.
3. British Columbia Safety Authority. The facts about
aluminum wiring in the home. New Westminster, British
Columbia, Canada: British Columbia Safety Authority;
no date. Available from URL: http://www.safetyauthority.
ca/ services/esp/The_Facts_About_Aluminum_Wiring_
In_The_Home.pdf.
4. Consumer Product Safety Commission. May is National
Electrical Safety Month: good news for
homeowners-aluminum wiring fix still available.
Washington, DC: Consumer Product Safety Commission;
2003. Available from URL: http://www.cpsc.gov/
CPSCPUB/PREREL/prhtml03/03120.html.
5. Consumer Product Safety Commission. CPSC safety
recommendations for aluminum wiring in homes.
Washington, DC: Consumer Product Safety Commission;
1974. Available from URL: http://www.cpsc.gov/
CPSCPUB/PREREL/prhtml74/74040.html.
6. AWG American wire gauge/diameter/resistance. Cologne,
Germany: Bernd Noack; no date. Available from URL:
http://www.bnoack.com/data/wire-resistance.html.
7. Consumer Product Safety Commission. Extension cords
fact sheet. Washington, DC: Consumer Product Safety
Commission; no date. CPSC #16. Available from URL:
http://www.cpsc.gov/CPSCPUB/PUBS/16.html.
Additional Sources of Information
Croft T, Summers W. American electricians’ handbook.
14th edition, New York: McGraw-Hill Professional; 2002.
Tuck D, Tuck G, Woodson RD. Electrician’s instant
answers. New York: McGraw-Hill Professional; 2003.
Black and Decker. The complete guide to home wiring: a
comprehensive manual, from basic repairs to advanced
projects (Black & Decker Home Improvement Library;
US edition). Chanhassen, MN: Creative Publishing
International; 2001.
Sunset Publishing. Basic wiring. 3rd edition. Menlo Park,
CA: Sunset Books, 1995.
11-17Chapter 11: ElectricityHealthy Housing Reference Manual
Hometime.com. Electrical service panel: panel components, circuit breakers, fuses, electrical glossary.
Hometime.com; no date. Available from URL:
http://www.hometime.com/Howto/ projects/electric/
elec_2.htm.
Vandervort D. How your house works: electric systems.
Glendale, CA: Hometips.com; no date. Available from
URL: http://www.hometips.com/hyhw/electrical/electric.
html.
PNM Resources. Residential subdivisions: electric service
requirements. In: Electric service guide. Albuquerque,
NM: PNM; 2004. Available from URL:
http://www.pnm.com/esg/chapters/56-63.pdf.
Textor K. Extension cord basics. Fine Homebuilding
2000, 129: 84-9. Available from URL:
http://www.taunton.com/finehomebuilding/pages/
h00010.asp.
Consumer Product Safety Commission. Repairing aluminum wiring. Washington, DC: Consumer Product Safety
Commission; 1994. CPSC #516. Available from URL:
http://www.cpsc.gov/CPSCPUB/PUBS/516.pdf.
Healthy Housing Reference Manual11-18 Chapter 11: Electricity
12-1Chapter 12: Heating, Air Conditioning, and VentilatingHealthy Housing Reference Manual
“Our climate is warming at a faster rate than ever before
recorded.”
D. James Baker
NOAA Administrator, 1993–2004
Introduction
The quotes below provide a profound lesson in the need
for housing to provide protection from both the heat and
cold.
“France heat wave death toll set at 14,802: The death
toll in France from August’s blistering heat wave has
reached nearly 15,000, according to a governmentcommissioned report released Thursday, surpassing a
prior tally by more than 3,000.” USA Today,
September 25, 2003.
“In the study of the 1995 Chicago heat wave, those at
greatest risk of dying from the heat were people with
medical illnesses who were socially isolated and did
not have access to air conditioning.” Centers for
Disease Control and Prevention, Morbidity and
Mortality Weekly Report, July 4, 2003.
“3 Deaths tied to cold…The bitter cold that gripped
the Northeast through the weekend and iced over
roads was blamed for at least three deaths, including
that of a Philadelphia man found inside a home without heat.” Lexington [Kentucky] Herald Leader,
January 12, 2004.
Chapter 12: Heating, Air Conditioning, and Ventilating
Air duct— A formed conduit that carries warm or cold air from the furnace or air-conditioner and back again.
Antiflooding Control— A safety control that shuts off fuel and ignition when excessive fuel oil accumulates in the appliance.
Appliance:
• High heat— A unit that operates with flue entrance temperature of combustion products above 1,500°F (820°C).
• Medium heat— Same as high-heat, except above 600°F (320°C).
• Low heat— same as high-heat, except below 600°F (320°C).
Boiler:
• High pressure— A boiler furnishing pressure at 15 psi or more.
• Low pressure (hot water or steam)— A boiler furnishing steam at a pressure less than 15 psi or hot water not more
than 30 psi.
Burner— A device that mixes fuel, air, and ignition in a combustion chamber.
Definitions of Terms Related to HVAC Systems
“In many temperate countries, death rates during the
winter season are 10%–25% higher than those in the
summer.” World Health Organization, Health
Evidence Network, November 1, 2004.
This chapter provides a general overview of the heating
and cooling of today’s homes. Heating and cooling are not
merely a matter of comfort, but of survival. Both very
cold and very hot temperatures can threaten health.
Excessive exposure to heat is referred to as heat stress and
excessive exposure to cold is referred to as cold stress.
In a very hot environment, the most serious health risk is
heat stroke. Heat stroke requires immediate medical attention and can be fatal or leave permanent damage. Heat
stroke fatalities occur every summer. Heat exhaustion and
fainting are less serious types of illnesses. Typically they
are not fatal, but they do interfere with a person’s ability
to work.
At very cold temperatures, the most serious concern is the
risk for hypothermia or dangerous overcooling of the
body. Another serious effect of cold exposure is frostbite
or freezing of exposed extremities, such as fingers, toes,
nose, and ear lobes. Hypothermia can be fatal if immediate medical attention is not received.
Heat and cold are dangerous because the victims of heat
stroke and hypothermia often do not notice the symptoms. This means that family, neighbors, and friends are
essential for early recognition of the onset of the conditions. The affected individual’s survival depends on others
Healthy Housing Reference Manual12-2 Chapter 12: Heating, Air Conditioning, and Ventilating
Heat stroke signs and symptoms include sudden and
severe fatigue, nausea, dizziness, rapid pulse, lightheadedness, confusion, unconsciousness, extremely high temperature, and hot and dry skin surface. An individual who
appears disorientated or confused, seems euphoric or
unaccountably irritable, or suffers from malaise or flulike
symptoms should be moved to a cool location and medical advice should be sought immediately.
to identify symptoms and to seek medical help. Family,
neighbors, and friends must be particularly diligent during heat or cold waves to check on individuals who live
alone.
Although symptoms vary from person to person, the
warning signs of heat exhaustion include confusion and
profuse and prolonged sweating. The person should be
removed from the heat, cooled, and heavily hydrated.
Carbon monoxide (CO) detector— A device used to detect CO (specific gravity of 0.97 vs. 1.00 for oxygen, a colorless
odorless gas resulting from combustion of fuel). CO detectors should be placed on each floor of the structure at eye level and
should have an audible alarm and, when possible, a digital readout at eye level.
Chimney— A vertical shaft containing one or more passageways.
Factory-built chimney— A tested and accredited flue for venting gas appliances, incinerators and solid or liquid
fuel-burning appliances.
Masonry chimney— A field-constructed chimney built of masonry and lined with terra cotta flue or firebrick.
Metal chimney— A field-constructed chimney of metal.
Chimney connector— A pipe or breeching that connects the heating appliance to the chimney.
Clearance— The distance separating the appliance, chimney connector, plenum, and flue from the nearest surface of
combustible material.
Central cooling system— An electric or gas-powered system containing an outside compressor, cooling coils, and a ducting
system inside the structure designed to supply cool air uniformly throughout the structure.
Central heating system— A flue connected boiler or furnace installed as an integral part of the structure and designed to
supply heat adequately for the structure.
Collectors— The key component of active solar systems and are designed to meet the specific temperature requirements and
climate conditions for different end uses. Several types of solar collectors exist: flat-plate collectors, evacuated-tube collectors,
concentrating collectors, and transpired air collectors.
Controls:
• High-low limit control— An automatic control that responds to liquid level changes and will shut down if they are
exceeded.
• Primary safety control— The automatic safety control intended to prevent abnormal discharge of fuel at the burner in
case of ignition failure or flame failure.
Combustion safety control— A primary safety control that responds to flame properties, sensing the presence of flame and
causing fuel to be shut off in event of flame failure.
Convector— A radiator that supplies a maximum amount of heat by convection, using many closely spaced metal fins fitted
onto pipes that carry hot water or steam and thereby heat the circulating air.
Conversion— A boiler or furnace, flue connected, originally designed for solid fuel but converted for liquid or gas fuel.
Damper— A valve for regulating draft on coal-fired equipment. Generally located on the exhaust side of the combustion
chamber, usually in the chimney connector. Dampers are not allowed on oil- and gas-fired equipment.
Draft hood— A device placed in and made a part of the vent connector (chimney connector or smoke pipe) from an appliance, or in the appliance itself. The hood is designed to a) ensure the ready escape of the products of combustion in the event
of no draft, back draft, or stoppage beyond the draft hood; b) prevent backdraft from entering the appliance; and c) neutralize the effect of stack action of the chimney flue upon appliance operation.
Definitions of Terms Related to HVAC Systems
12-3Chapter 12: Heating, Air Conditioning, and VentilatingHealthy Housing Reference Manual
Draft regulator— A device that functions to maintain a desired draft in oil-fired appliances by automatically reducing the
chimney draft to the desired value. Sometimes this device is referred to in the field as air-balance, air-stat, or flue velocity
control or barometer damper.
Fuel oil— A liquid mixture or compound derived from petroleum that does not emit flammable vapor below a temperature
of 125°F (52°C).
Heat— The warming of a building, apartment, or room by a furnace or electrical stove.
Heating plant— The furnace, boiler, or the other heating devices used to generate steam, hot water, or hot air, which then is
circulated through a distribution system. It typically uses coal, gas, oil or wood as its source of heat.
Limit control— A thermostatic device installed in the duct system to shut off the supply of heat at a predetermined temperature of the circulated air.
Oil burner— A device for burning oil in heating appliances such as boilers, furnaces, water heaters, and ranges. A burner of
this type may be a pressure-atomizing gun type, a horizontal or vertical rotary type, or a mechanical or natural draft-vaporizing type.
Oil stove— A flue-connected, self-contained, self-supporting oil-burning range or room heater equipped with an integral
tank not exceeding 10 gallons; it may be designed to be connected to a separate oil tank.
Plenum chamber— An air compartment to which one or more distributing air ducts are connected.
Pump, automatic oil— A device that automatically pumps oil from the supply tank and delivers it in specific quantities to
an oil-burning appliance. The pump or device is designed to stop pumping automatically if the oil supply line breaks.
Radiant heat— A method of heating a building by means of electric coils, hot water, or steam pipes installed in the floors,
walls, or ceilings.
Register— A grille-covered opening in a floor, ceiling, or wall through which hot or cold air can be introduced into a room.
It may or may not be arranged to permit closing the grille.
Room heater— A self-contained, freestanding heating appliance (space heater) intended for installation in the space being
heated and not intended for duct connection.
Smoke detector— A device installed in several rooms of the structure to warn of the presence of smoke. It should provide an
audible alarm. It can be battery powered or electric, or both. If the unit is battery powered, the batteries should be tested or
checked on a routine basis and changed once per year. If the unit is equipped with a 10-year battery, it is not necessary to replace the battery every year.
Tank— A separate tank connected, directly or by pump, to an oil-burning appliance.
Thimble— A metal or terra cotta lining for a chimney or furnace pipe.
Valve (main shut-off valve)— A manually operated valve in an oil line used to turn the oil supply to the burner on or off.
Vent system— The gas vent or chimney and vent connector, if used, assembled to form a continuous, unobstructed passageway from the gas appliance to the outside atmosphere to remove vent gases.
Definitions of Terms Related to HVAC Systems
Warning signs of hypothermia include nausea, fatigue,
dizziness, irritability, or euphoria. Individuals also experience pain in their extremities (e.g., hands, feet, ears) and
severe shivering. People who exhibit these symptoms, particularly the elderly and young, should be moved to a
heated shelter and medical advice should be sought when
appropriate.
The function of a heating, ventilation, and air
conditioning (HVAC) system is to provide for more than
human health and comfort. The HVAC system produces
heat, cool air, and ventilation, and helps control dust and
moisture, which can lead to adverse health effects. The
variables to be controlled are temperature, air quality, air
motion, and relative humidity. Temperature must be
maintained uniformly throughout the heated/cooled area.
There is a 6°F to 10°F (-14°C to -12°C) variation in
room temperature from floor to ceiling. The adequacy of
the HVAC system and the air-tightness of the structure
or room determine the degree of personal safety and
comfort within the dwelling.
Healthy Housing Reference Manual12-4 Chapter 12: Heating, Air Conditioning, and Ventilating
Gas, electricity, oil, coal, wood, and solar energy are the
main energy sources for home heating and cooling. Heating
systems commonly used are steam, hot water and hot air.
A housing inspector should have knowledge of the
various heating fuels and systems to be able to determine
their adequacy and safety in operation. To cover fully all
aspects of the heating and cooling system, the entire area
and physical components of the system must be considered.
Heating
Fifty-one percent of the homes in the United States are
heated with natural gas, 30% are heated with electricity,
and 9% with fuel oil. The remaining 11% are heated
with bottled fuel, wood, coal, solar, geothermal, wind, or
solar energy [1]. Any home using combustion as a source
of heating, cooling, or cooking or that has an attached
garage should have appropriately located and maintained
carbon monoxide (CO) gas detectors. According to the
U.S. Consumer Product Safety Commission (CPSC),
from data collected in 2000, CO kills 200 people and
sends more than 10,000 to the hospital each year.
The standard fuels for heating are discussed below.
Standard Fuels
Gas
More than 50% of American homes use gas fuel. Gas
fuels are colorless gases. Some have a characteristic pungent
odor; others are odorless and cannot be detected by smell.
Although gas fuels are easily handled in heating equipment,
their presence in air in appreciable quantities becomes a
serious health hazard. Gases diffuse readily in the air,
making explosive mixtures possible. A proportion of
combustible gas and air that is ignited burns with such a
high velocity that an explosive force is created. Because of
these characteristics of gas fuels, precautions must be
taken to prevent leaks, and care must be exercised when
gas-fired equipment is lit.
Gas is broadly classified as natural or manufactured.
• Natural gas— This gas is a mixture of several
combustible and inert gases. It is one of the richest
gases and is obtained from wells ordinarily located in
petroleum-producing areas. The heat content may vary
from 700 to 1,300 British thermal units (BTUs) per
cubic foot, with a generally accepted average figure of
1,000 BTUs per cubic foot. Natural gases are
distributed through pipelines to the point of use and
are often mixed with manufactured gas to maintain a
guaranteed BTU content.
• Manufactured gas— This gas, as distributed, is usually
a combination of certain proportions of gases
produced from coke, coal, and petroleum. Its BTU
value per cubic foot is generally closely regulated, and
costs are determined on a guaranteed BTU basis,
usually 520 to 540 BTUs per cubic foot.
• Liquefied petroleum gas— Principal products of
liquefied petroleum gas are butane and propane.
Butane and propane are derived from natural gas or
petroleum refinery gas and are chemically classified as
hydrocarbon gases. Specifically, butane and propane
are on the borderline between a liquid and a gaseous
state. At ordinary atmospheric pressure, butane is a gas
above 33°F (0.6°C) and propane a gas at -42°F
(-41°C). These gases are mixed to produce commercial
gas suitable for various climatic conditions. Butane
and propane are heavier than air. The heat content of
butane is 3,274 BTUs per cubic foot, whereas that of
propane is 2,519 BTUs per cubic foot.
Gas burners should be equipped with an automatic shutoff in case the flame fails. Shutoff valves should be
located within 1 foot of the burner connection and on
the output side of the meter.
Caution: Liquefied petroleum gas is heavier than air;
therefore, the gas will accumulate at the bottom of confined areas. If a leak develops, care should be taken to
ventilate the appliance before lighting it.
Electricity
Electricity has gained popularity for heating in many
regions, particularly where costs are competitive with
other sources of heat energy, with usage increasing from
2% in 1960 to 30% in 2000. With an electric system, the
housing inspector should rely mainly on the electrical
inspector to determine proper installation. There are a
few items, however, to be concerned with to ensure safe
use of the equipment. Check to see that the units are
approved by an accredited testing agency and installed
according to the manufacturer’s specifications. Most convector-type units must be installed at least 2 inches above
the floor level, not only to ensure that proper convection
currents are established through the unit, but also to
allow sufficient air insulation from any combustible flooring material. The housing inspector should check for curtains that extend too close to the unit or loose, long-pile
rugs that are too close. A distance of 6 inches on the floor
and 12 inches on the walls should separate rugs or curtains from the appliance.
12-5Chapter 12: Heating, Air Conditioning, and VentilatingHealthy Housing Reference Manual
Heat pumps are air conditioners that contain a valve that
allows switching between air conditioner and heater.
When the valve is switched one way, the heat pump acts
like an air conditioner; when it is switched the other way,
it reverses the flow of refrigerants and acts like a heater.
Cold is the absence of energy or calories of heat. To cool
something, the heat must be removed; to warm something, energy or calories of heat must be provided. Heat
pumps do both.
A heat pump has a few additions beyond the typical air
conditioner: a reversing valve, two thermal expansion
valves, and two bypass valves. The reversing valve allows
the unit to provide both cooling and heating. Figure 12.1
shows a heat pump in cooling mode. The unit operates as
follows:
• The compressor compacts the refrigerant vapor and
pumps it to the reversing valve.
• The reversing valve directs the compressed vapor to
flow to the outside heat exchanger (condenser), where
the refrigerant is cooled and condensed to a liquid.
• The air blowing through the condenser coil removes
heat from the refrigerant.
• The liquid refrigerant bypasses the first thermal
expansion valve and flows to the second thermal
expansion valve at the inside heat exchanger
(evaporator) where it expands into the evaporator and
becomes vapor.
• The refrigerant picks up heat energy from the air
blowing across the evaporator coil and cool air comes
out at the other side of the coil. The cool air is ducted
to the occupied space as air-conditioned air.
• The refrigerant vapor then goes back to the reversing
valve to be directed to the compressor to start the
refrigeration cycle all over again.
Figure 12.1. Heat Pump in Cooling Mode [2]
Heat pumps [3] are quite efficient in their use of energy.
However, heat pumps often freeze up; that is, the coils in
the outside air collect ice. The heat pump has to melt
this ice periodically, so it switches itself back to air conditioner mode to heat up the coils. To avoid pumping
cold air into the house in air conditioner mode, the heat
pump also uses electric strip heaters to heat the cold air
that the air conditioner is pumping out. Once the ice is
melted, the heat pump switches back to heating mode
and turns off the burners.
Radiant heat warms objects directly with longwave electromagnetic energy. The heating panels diffuse heating
energy rays in a 160° arc, distributing warmth evenly.
The goal is to achieve no more than a 4°F (-16°C) difference in temperature between floor level and ceiling level.
When properly installed, radiant heat warms a room
sooner and at lower temperature settings than do other
kinds of heat. Extreme care must be taken to protect
against fire hazards from objects in close proximity to the
infrared radiation reflectors. Inspectors dealing with this
heat source should have specialized training. Radiant
heating is plastered into the ceiling or wall in some
homes or in the brick or ceramic floors of bathrooms. If
wires are bare in the plaster, they should be treated as
open and exposed wiring. The inspector should be
knowledgeable about these systems, which are technical
and relatively new.
Fuel Oil
Fuel oils are derived from petroleum, which consists primarily of compounds of hydrogen and carbon (hydrocarbons) and smaller amounts of nitrogen and sulfur.
Domestic fuel oils are controlled by rigid specifications.
Six grades of fuel oil— numbered 1 through 6— are generally used in heating systems; the lighter two grades are
used primarily for domestic heating:
• Grade Number 1— a volatile, distillate oil for use in
burners that prepare fuel for burning solely by
vaporization (oil-fired space heaters).
• Grade Number 2— a moderate weight, volatile,
distillate oil used for burners that prepare oil for
burning by a combination of vaporization and
atomization. This grade of oil is commonly used in
domestic heating furnaces.
Heating values of oil vary from approximately 152,000
BTU per gallon for number 6 oil to 136,000 BTU per
gallon for number 1 oil. Oil is more widely used today
than coal and provides a more automatic source of heat
and comfort. It also requires more complicated systems
Healthy Housing Reference Manual12-6 Chapter 12: Heating, Air Conditioning, and Ventilating
and controls. If the oil supply is in the basement or cellar
area, certain code regulations must be followed (Figure
12.2) [4–7]. No more than two 275-gallon tanks may be
installed above ground in the lowest story of any one
building. The IRC recommends a maximum fuel oil storage of 660 gallons. The tank shall not be closer than 7
feet horizontally to any boiler, furnace, stove, or exposed
flame(s).
Fuel oil lines should be embedded in a concrete or
cement floor or protected against damage if they run
across the floor. Each tank must have a shutoff valve that
will stop the flow if a leak develops in the line to or in
the burner itself. A leak-tight liner or pan should be
installed under tanks and lines located above the floor.
They contain potential leaks so the oil does not spread
over the floor, creating a fire hazard.
The tank or tanks must be vented to the outside, and a
gauge showing the quantity of oil in the tank or tanks
must be tight and operative. Steel tanks constructed
before 1985 had a life expectancy of 12–20 years. Tanks
must be off the floor and on a stable base to prevent settlement or movement that may rupture the connections.
Figure 12.3 shows a buried outside tank installation. In
1985, federal legislation was passed requiring that the
exterior components of underground storage tanks
(USTs) installed after 1985 resist the effects of pressure,
vibration, and movement. Federal regulations for USTs
exclude the following: farm and residential tanks of 1,100
gallons (420 liters) or less capacity; tanks storing heating
oil used on the premises; tanks on or above the floor of
basements; septic tanks; flow-through process tanks; all
tanks with capacity of 110 gallons or less; and emergency
spill and overfill tanks [8]. A review of local and state
regulations should be completed before installing underground tanks because many jurisdictions do not allow
burial of gas or oil tanks.
Figure 12.2. Piping Hookup for Inside Tank Installation [4] Figure 12.3. Piping Hookup for Buried Outside Tank [4]
Coal
The four types of coal are anthracite, bituminous, subbituminous, and lignite. Coal is prepared in many sizes
and combinations of sizes. The combustible portions of
the coal are fixed carbons, volatile matter (hydrocarbons),
and small amounts of sulfur. In combination with these
are noncombustible elements composed of moisture and
impurities that form ash. The various types differ in heat
content. Heat content is determined by analysis and is
expressed in British thermal units per pound.
Improper coal furnace operation can result in an
extremely hazardous and unhealthy home. Ventilation of
the area surrounding the furnace is very important to prevent heat buildup and to supply air for combustion.
Solar Energy
Solar energy has gained popularity in the last 25 years as
the cost of installation of solar panels and battery storage
has decreased. Improved technology with panels,
installation of panels, piping, and batteries has created a
much larger market. Solar energy largely has been used to
heat water. Today, there are more than a million solar
water-heating systems in the United States. Solar water
heaters use direct sun to heat either water or a
heat-transfer fluid in collectors [3]. That water is then
stored for use as needed, with a conventional system
providing any necessary additional heating. A typical
system will reduce the need for conventional water
heating by about two-thirds, minimizing the cost of
electricity or the use of fossil fuel and thus the
environmental impact associated with their use. The U.S.
Department of Housing and Urban Development and
the U.S. Department of Energy (DOE) have instituted
initiatives to deploy new solar technologies in the next
generation of American housing [3]. For example, DOE
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has the Million Solar Roofs Initiative begun in 1997 to
install solar energy systems in more than 1 million U.S.
buildings by 2010.
Central Heating Units
The boiler should be placed in a separate room whenever
possible, which is usually required in new construction.
In most housing inspections, however, the inspector is
dealing with existing conditions and must adapt the situation as closely as possible to acceptable safety standards.
In many old buildings, the furnace is located in the center of the cellar or basement. This location does not lend
itself to practical conversion to a boiler room.
Consider the physical requirements for a boiler or
furnace.
• Ventilation— More circulating air is required for the
boiler room than for a habitable room, to reduce the
heat buildup caused by the boiler or furnace and to
supply oxygen for combustion.
• Fire protection rating— As specified by various codes
(fire code, building code, and insurance underwriters),
the fire regulations must be strictly adhered to in areas
surrounding the boiler or furnace. This minimum
clearance for a boiler or furnace from a wall or ceiling
is shown in Figures 12.4 and 12.5.
Asbestos was used in numerous places on furnaces to protect buildings from fire and to prevent lost heat. Figure
12.6 shows asbestos-coated heating ducts, for example.
Where asbestos insulation is found, it must be handled
with care (breathing protection and protective clothing)
and care must be taken to prevent or contain release into
the air [10].
The furnace or boiler makes it difficult to supply air and
ventilation for the room. Where codes and local authority
permit, it may be more practical to place the furnace or
boiler in an open area. The ceiling above the furnace
should be protected to a distance of 3 feet beyond all
Figure 12.5. Minimum Clearance for Steam or Hot Water Boiler and
Mechanical Warm-air Furnace [4]
Figure 12.6. Heating Ducts Covered With Asbestos Insulation
Figure 12.4. Minimum Clearance for Pipeless Hot Air and Gravity Warm
Air Furnace [4]
furnace or boiler appurtenances, and this area should be
free of all storage material. The furnace or boiler should
be on a firm foundation of concrete if located in the cellar or basement. If codes permit furnace installations on
the first floor, then they must be consulted for proper setting and location.
Heating Boilers
The term boiler is applied to the single heat source that
can supply either steam or hot water (a boiler is often
called a heater).
Boilers may be classified according to several kinds of
characteristics. They are typically made from cast iron or
steel. Their construction design may be sectional, portable, fire-tube, water-tube, or special. Domestic heating
boilers are generally of low-pressure type with a maximum working pressure of 15 pounds per square inch
(psi) for steam and 30 psi for hot water. All boilers have a
combustion chamber for burning fuel. Automatic fuel-firing devices help supply the fuel and control the combusHealthy Housing Reference Manual12-8 Chapter 12: Heating, Air Conditioning, and Ventilating
tion. Hand firing is accomplished by the provision of a
grate, ash pit, and controllable drafts to admit air under
the fuel bed and over it through slots in the firing door.
A check draft is required at the smoke pipe connection to
control chimney draft. The gas passes from the combustion chamber to the flue passages (smoke pipe) designed
for maximum possible transfer of heat from the gas.
Provisions must be made for cleaning flue passages.
Cast-iron boilers are usually shipped in sections and
assembled at the site. They are generally classified as
• square or rectangular boilers with vertical sections; and
• round, square, or rectangular boilers with horizontal
pancake sections.
Most steel boilers are assembled units with welded steel
construction and are called portable boilers. Large boilers
are installed in refractory brick settings on the site. Above
the combustion chamber, a group of tubes is suspended,
usually horizontally, between two headers. If flue gases
pass through the tubes and water surrounds them, the
boiler is designated as the fire-tube type. When water
flows through the tubes, it is termed water-tube. Firetube is the predominant type.
Heating Furnaces
Heating furnaces are the heat sources used when air is the
heat-carrying medium. When air circulates because of the
different densities of the heated and cooled air, the furnace is a gravity type. A fan may be included for the air
circulation; this type is called a mechanical warm-air furnace. Furnaces may be of cast iron or steel and burn various types of fuel.
Some new furnaces are as fuel efficient as 95%. Furnaces
with an efficiency of 90% or greater use two heat
exchangers instead of one. Energy savings come not only
from the increased efficiency, but also from improved
comfort at lower thermostat settings.
Fuel-burning Furnaces
Some localities throughout the United States still use coal
as a heating fuel, including residences, schools, colleges
and universities, small manufacturing facilities, and other
facilities located near coal sources.
In many older furnaces, the coal is stoked or fed into the
firebox by hand. The single-retort, underfeed-type bituminous coal stoker is the most commonly used domestic
automatic-stoking steam or hot-water boiler (Figure
12.7). The stoker consists of a coal hopper, a screw for
conveying coal from hopper to retort, a fan that supplies
Figure 12.7. Typical Underfeed Coal Stoker Installation in Small Boilers [4]
air for combustion, a transmission for driving coal feed
and fan, and an electric motor for supplying power. The
air for combustion is admitted to the fuel through tuyeres
(air inlets) at the top of the retort. The stoker feeds coal
to the furnace intermittently in accordance with temperature or pressure demands.
Oil burners are broadly designated as distillate, domestic,
and commercial or industrial. Distillate burners are usually found in oil-fired space heaters. Domestic oil burners
are usually power driven and are used in domestic heating
plants. Commercial or industrial burners are used in
larger central-heating plants for steam or power
generation.
Domestic oil burners vaporize and atomize the oil and
deliver a predetermined quantity of oil and air to the
combustion chambers. Domestic oil burners operate
automatically to maintain a desired temperature.
Gun-type burners atomize the oil either by oil pressure or
by low-pressure air forced through a nozzle. The oil system pressure-atomizing burner consists of a strainer,
pump, pressure-regulating valve, shutoff valve and atomizing nozzle. The air system consists of a power-driven
fan and an air tube that surrounds the nozzle and electrode assembly.
The fan and oil pump are generally connected directly to
the motor. Oil pressures normally used are about 100 psi,
but pressures considerably in excess of this are sometimes
used.
The form and parts of low-pressure, air-atomizing burners are similar to high-pressure atomizing (gun) burners
(Figure 12.8) except for addition of a small air pump and
a different way of delivering air and oil to the nozzle or
orifice.
The atomizing type burner, sometimes known as a radiant or suspended flame burner, atomizes oil by throwing
12-9Chapter 12: Heating, Air Conditioning, and VentilatingHealthy Housing Reference Manual
it from the circumference of a rapidly rotating motordriven cup. The burner is installed so that the driving
parts are protected from the heat of the flame by a hearth
of refractory material at about the grate elevation. Oil is
fed by pump or gravity; the draft is mechanical or a combination of natural and mechanical.
Horizontal rotary burners were originally designed for
commercial and industrial use but are available in sizes
suitable for domestic use. In this burner, fuel oil being
thrown in a conical spray from a rapidly rotating cup is
atomized. Horizontal rotary burners use electric gas or
gas-pilot ignition and operate with a wide range of fuels,
primarily Numbers 1 and 2 fuel oil. Primary safety controls for burner operation are necessary. An antiflooding
device must be a part of the system to stop oil flow if
ignition in the burner should fail. Likewise, a stack control is necessary to shut off the burner if the stack temperatures are exceeded, thus cutting off all power to the
burner. This button must be reset before starting can be
attempted. The newer models now use electric eye-type
control on the burner itself.
On the basis of the method used to ignite fuels, burners
are divided into five groups:
• Electric— A high-voltage electric spark in the path of
an oil and air mixture causes ignition. This electric
spark may be continuous or may operate only long
enough to ignite the oil. Electric ignition is almost
universally used. Electrodes are located near the
nozzles, but not in the path of the oil spray.
• Gas pilot— A small gas pilot light that burns
continuously is frequently used. Gas pilots usually
have expanded gas valves that automatically increase
flame size when a motor circuit starts. After a fixed
interval, the flame reverts to normal size (Figure 12.9).
Figure 12.8. Cutaway View of Typical High-pressure Gun Burner [4]
Figure 12.9. Gas-fired Boiler
Source: HUD
• Electric gas— An electric spark ignites a gas jet, which
in turn ignites the oil-air mixture.
• Oil pilot— A small oil flame is used.
• Manual— A burning wick or torch is placed in the
combustion space through peepholes and thus ignites
the charge. The operator should stand to one side of
the fire door to guard against injury from chance
explosion.
The refractory lining or material should be an insulating
fireproof bricklike substance, never ordinary firebrick.
The insulating brick should be set on end to build a
2½-inch-thick wall from furnace to furnace. The size and
shape of the refractory pot vary from furnace to furnace.
The shape can be either round or square, whichever is
more convenient to build. It is more important to use a
special cement having properties similar to that of the
insulating refractory-type brick.
Steam Heating Systems
Steam heating systems are classified according to the pipe
arrangement, accessories used, method of returning the
condensate to the boiler, method of expelling air from the
system, or the type of control used. The successful
operation of a steam heating system consists of generating
steam in sufficient quantity to equalize building heat loss
at maximum efficiency, expelling entrapped air, and
returning all condensate to the boiler rapidly. Steam
Healthy Housing Reference Manual12-10 Chapter 12: Heating, Air Conditioning, and Ventilating
cannot enter a space filled with air or water at pressure
equal to the steam pressure. It is important, therefore, to
eliminate air and remove water from the distribution
system. All hot pipelines exposed to contact by residents
must be properly insulated or guarded. Steam heating
systems use the following methods to return the
condensate to the boiler:
• Gravity one-pipe air-vent system— One of the
earliest types used, this method returns condensate to
the boiler by gravity. This system is generally found in
one-building-type heating systems. The steam is
supplied by the boiler and carried through a single
system or pipe to radiators, as shown in Figure 12.10.
Return of the condensate is dependent on hydrostatic
head. Therefore, the end of the stream main, where it
attaches to the boiler, must be full of water (termed a
wet return) for a distance above the boiler line to
create a pressure drop balance between the boiler and
the stream main.
Radiators are equipped with an inlet valve and an air
valve. The air valve permits venting of air from the
radiator and its displacement by steam. Condensate is
drained from the radiator through the same pipe that
supplies steam.
• Two-pipe steam vapor system with return trap—
The two-pipe vapor system with boiler return trap and
air eliminator is an improvement of the one-pipe
system. The return connection of the radiator has a
thermostatic trap that permits flow of condensate and
air only from the radiator and prevents steam from
leaving the radiator. Because the return main is at
atmospheric pressure or less, a boiler return trap is
installed to equalize condensate return pressure with
boiler pressure.
Water Heating Systems
All water heating systems are similar in design and
operating principle. The one-pipe gravity water heating
system is the most elementary of the gravity systems and
is shown in Figure 12.10. Water is heated at the lowest
point in the system. It rises through a single main because
of a difference in density between hot and cold water.
The supply rise or radiator branch takes off from the top
of the main to supply water to the radiators. After the
water gives up heat in the radiator, it goes back to the
same main through return piping from the radiator. This
cooler return water mixes with water in the supply main
and causes the water to cool a little. As a result, the next
radiator on the system has a lower emission rate and must
be larger. Figure 12.10. Typical Gravity One-pipe Heating System [4]
Note in Figure 12.11 that the high points of the hot
water system are vented and the low points are drained.
In this case, the radiators are the high points and the
heater is the low point.
• One-pipe forced-feed system— If a pump or
circulator is introduced in the main near the heater of
the one-pipe system, it becomes a forced system that
can be used for much larger applications than can the
gravity type. This system can operate at higher water
temperatures than the gravity system can. When the
water is moving faster and at higher temperatures, it
makes a more responsive system, with smaller
temperature drops and smaller radiators for the same
heating load.
• Two-pipe gravity system— A one-pipe gravity system
may become a two-pipe system if the return radiator
branch connects to a second main that returns water
to the heater (Figure 12.12). Water temperature is
practically the same in the entire radiator.
• Two-pipe forced-circulation system— This system is
similar to a one-pipe forced-circulation system except
that it uses the same piping arrangement found in the
two-pipe gravity system.
• Expansion tanks— When water is heated, it tends to
expand. Therefore, an expansion tank is necessary in a
hot water system. The expansion tank, either open or
closed, must be of sufficient size to permit a change in
water volume within the heating system. If the
expansion tank is open, it must be placed at least 3
feet above the highest point of the system. It will
require a vent and an overflow. The open tank is
usually in an attic, where it needs protection from
freezing.
The closed expansion tank is found in modern installations. An air cushion in the tank compresses and
12-11Chapter 12: Heating, Air Conditioning, and VentilatingHealthy Housing Reference Manual
expands according to the change of volume and pressure in the system. Closed tanks are usually at the low
point in the system and close to the heater. They can,
however, be placed at almost any location within the
heating system.
Air Heating Systems
Gravity Warm-air Heating Systems. These operate
because of the difference in specific gravity of warm air
and cold air. Warm air is lighter than cold air and rises if
cold air is available to replace it (Figure 12.13).
• Operation— Satisfactory operation of a gravity warmair heating system depends on three factors: size of
warm air and cold air ducts, heat loss of the building,
and heat available from the furnace.
• Heat distribution— The most common source of
trouble in these systems is insufficient pipe area,
usually in the return or cold air duct. The total crosssection area of the cold duct or ducts must be at least
equal to the total cross-section area of all warm ducts.
• Pipeless furnaces— The pipeless hot-air furnace is the
simplest type of hot-air furnace and is suitable for
small homes where all rooms can be grouped about a
single large register. Other pipeless gravity furnaces are
often installed at floor level. These are really oversized
jacketed space heaters. The most common difficulty
experienced with this type of furnace is supplying a
return air opening of sufficient size on the floor.
Forced Warm-air Heating Systems. The mechanical
warm-air furnace is the most modern type of warm-air
equipment (Figures 12.13 and 12.14). It is the safest type
because it operates at low temperatures. The principle of
Figure 12.11. One-pipe Gravity Water Heating System [4]
Figure 12.12. Two-pipe Gravity Water Heating System [4]
Figure 12.13. Warm-air Convection Furnace [4]
a forced-warm-air heating system is very similar to that of
the gravity system, except that a fan or blower is added to
increase air movement. Because of the assistance of the
fan or blower, the pitch of the ducts or leaders can be disregarded; therefore, it is practical to deliver heated air in
the most convenient places.
• Operation— In a forced-air system, operation of the
fan or blower must be controlled by air temperature in
a bonnet or by a blower control furnace stat. The
blower control starts the fan or blower when the
temperature reaches a certain point and turns the fan
or blower off when the temperature drops to a
predetermined point.
• Heat distribution— Dampers in the various warm-air
ducts control distribution of warm air either at the
branch takeoff or at the warm-air outlet. Humidifiers
are often mounted in the supply bonnet to regulate
the humidity within the residence.
Healthy Housing Reference Manual12-12 Chapter 12: Heating, Air Conditioning, and Ventilating
Space Heaters
Space heaters are the least desirable type of heating from
the viewpoint of fire safety and housing inspection. A
space heater is a self-contained, free-standing air-heating
appliance intended for installation in the space being
heated and not intended for duct connection. According
to the CPSC, consumers are not using care when purchasing and using space heaters. Approximately 21,800
residential fires are caused by space heaters a year, and
300 people die in these fires. An estimated 6,000 persons
receive hospital emergency room care for burn injuries
associated with contacting hot surfaces of space heaters,
mostly in nonfire situations.
Individuals using space heaters should use the heaters in
accordance with the following precautions:
• Read and follow the manufacturer’s operating
instructions. A good practice is to read aloud the
instructions and warning labels to all members of the
household to be certain that everyone understands
how to operate the heater safely. Keep the owner’s
manual in a convenient place to refer to when needed.
• Choose a space heater that has been tested and
certified by a nationally recognized testing laboratory.
These heaters meet specific safety standards.
• Buy a heater that is the correct size for the area you
want to heat. The wrong size heater could produce
more pollutants and may not be an efficient use of
energy.
• Choose models that have automatic safety switches
that turn off the unit if it is tipped over accidentally.
• Select a space heater with a guard around the flame
area or heating element. Place the heater on a level,
hard, nonflammable surface, not on rugs or carpets or
near bedding or drapes. Keep the heater at least 3 feet
from bedding, drapes, furniture, or other flammable
materials.
Figure 12.14. Cross-sectional View of Building Showing Forced Warm-air
Heating System [4]
• Keep doors open to the rest of the house if you are
using an unvented fuel-burning space heater. This
helps prevent pollutant build-up and promotes proper
combustion. Follow the manufacturer’s instructions for
oil heaters to provide sufficient combustion air to
prevent CO production.
• Never leave a space heater on when you go to sleep.
Never place a space heater close to any sleeping person.
• Turn the space heater off if you leave the area. Keep
children and pets away from space heaters. Children
should not be permitted to either adjust the controls
or move the heater.
• Keep any portable heater as least 3 feet away from
curtains, newspapers, or anything that might burn.
• Have a smoke detector with fresh batteries on each
level of the house and a CO detector outside the
sleeping area. Install a CO monitor near oil space
heaters at the height recommended by the
manufacturer.
• Be aware that mobile homes require specially designed
heating equipment. Only electric or vented fuel-fired
heaters should be used.
• Have gas and kerosene space heaters inspected
annually.
• Do not hang items to dry above or on the heater.
• Keep all heaters out of exit and high-traffic areas.
• Keep portable electric heaters away from sinks, tubs,
and other wet or damp places to avoid deadly electric
shocks.
• Never use or store flammable liquids (such as gasoline)
around a space heater. The flammable vapors can flow
from one part of the room to another and be ignited
by the open flame or by an electrical spark.
Coal-fired Space Heaters (Cannon Stove)
A coal stove is made entirely of cast iron. Coal on the
grates receives primary air for combustion through the
grates from the ash-door draft intake. Combustible gases
driven from the coal by heat burn in the barrel of the
stove, where they receive additional or secondary air
through the feed door. The side and top of the stove
absorb the heat of combustion and radiate it to the surrounding space. Coal stoves must be vented to the flue.
12-13Chapter 12: Heating, Air Conditioning, and VentilatingHealthy Housing Reference Manual
Oil-fired Space Heaters
Oil-fired space heaters have atmospheric vaporizing-type
burners. The burners require a light grade of fuel oil that
vaporizes easily and in comparatively low temperatures.
In addition, the oil must be such that it leaves only a
small amount of carbon residue and ash within the
heater. Oil stoves must be vented.
The burner of an oil-fired space heater consists essentially
of a bowl, 8 to 13 inches in diameter, with perforations
in the side that admit air for combustion. The upper part
of the bowl has a flame ring or collar. Figure 12.15 shows
a perforated-sleeve burner. When several space heaters are
installed in a building, an oil supply from an outside tank
to all heaters is often desirable. Figure 12.16 shows the
condition of a burner flame with different rates of fuel
flow and indicates the ideal flame height.
Electric Space Heaters
Electric space heaters do not need to be vented.
Gas-fired Space Heaters
The three types of gas-fired space heaters (natural, manufactured, and liquefied petroleum gas) have a similar construction. All gas-fired space heaters must be vented to
prevent a dangerous buildup of poisonous gases. Each
unit console consists of an enamel steel cabinet with top
and bottom circulating grilles or openings, gas burners,
heating elements, gas pilot, and a gas valve. The heating
element or combustion chamber is usually cast iron.
Caution: All gas-fired space heaters and their connections
must be approved by the American Gas Association
(AGA). They must be
installed in accordance
with the recommendations of that organization or the local code.
Venting
Use of proper venting
materials and correct
installation of venting
for gas-fired space heaters is necessary to minimize harmful effects of
condensation and to
ensure that combustion
products are carried
off. (Approximately 12
gallons of water are
produced in the burn-Figure 12.15. Perforated-sleeve Burner Figure 12.16. Condition of Burner Flame with Different Rates of Fuel Flow [4]
ing of 1,000 cubic feet of natural gas. The inner surface
of the vent must therefore be heated above the dew point
of the combustion products to prevent water from forming in the flue.) A horizontal vent must be given an
upward pitch of at least 1 inch per foot of horizontal
distance.
When the smoke pipe extends through floors or walls,
the metal pipe must be insulated from the floor or wall
system by an air space (Figure 12.17). Sharp bends
should be avoided. A 9° vent elbow has a resistance to
flow equivalent to that of a straight section of pipe with a
length 10 times the elbow diameter. Be sure that vents are
of rigid construction and resistant to corrosion by flue gas
products. Several types of venting material are available
such as B-vent and other ceramic-type materials. A chimney lined with firebrick type of terra cotta must be
relined with an acceptable vent material if it is to be used
for venting gas-fired appliances.
The same size vent pipe should be used throughout its
length. A vent should never be smaller than the heater
outlet except when two or more vents converge from separate heaters. To determine the size of vents beyond the
point of convergence, one-half the area of each vent
should be added to the area of the largest heater’s vent.
Vents should be installed with male ends of inner liner
down to ensure condensate is kept within pipes on a cold
start. The vertical length of each vent or stack should be
at least 2 feet greater than the length between horizontal
connection and stack. Remember that the more conductive the unit, the lower the temperature of combustion
and the more byproducts of combustion are likely to be
Healthy Housing Reference Manual12-14 Chapter 12: Heating, Air Conditioning, and Ventilating
produced. These by-products are sometimes referred to as
soot and creosote. These by-products will build up in
vents, stacks, and chimneys. They are extremely flammable and can result in fire in these units that is hot enough
to penetrate the heat shielding and throw burning material onto the roof of the home.
The vent should be run at least 3 feet above any projection within 20 feet of the building to place it above a
possible pressure zone due to wind currents (Figure
12.18). A weather cap should prevent entrance of rain
and snow. Gas-fired space heaters, as well as gas furnaces
and water heaters, must be equipped with a backdraft
diverter (Figure 12.19) to protect heaters against downdrafts and excessive updrafts. Only draft diverters
approved by the AGA should be used.
The combustion chamber or firebox must be insulated
from the floor, usually with airspace of 15 to 18 inches.
The firebox is sometimes insulated within the unit and
thus allows for lesser clearance firebox combustibles.
Floors should be protected where coal space heaters are
located. The floor protection allows hot coals and ashes
to cool off if dropped while being removed from the ash
chamber. Noncombustible walls and materials should be
used when they are exposed to heated surfaces. For space
heaters, a top or ceiling clearance of 36 inches, a wall
clearance of 18 inches, and a smoke pipe clearance of 18
inches are recommended.
Hydronic Systems
Hydronic (circulating water) systems involving traditional
baseboards can be single-pipe or two-pipe. Radiant systems are also an option. All hydronic systems require an
expansion tank to compensate for the increase in water
volume when it is heated (i.e., the volume of 50°F [10°C]
Figure 12.17. Wall and Ceiling Clearance Reduction [4] Figure 12.18. Draft Relation to Height of Chimney [4]
water increases almost 4% when it is heated to 200°F
[93°C]). Single-pipe hydronic systems are most commonly used in residences. They use a single pipe with hot
water flowing in a series loop from radiator to radiator.
Massachusetts has a prototype set of hydronic systems
requirements [11].
The drawback to this arrangement is that the temperature
of the water decreases as it moves through each radiator.
Thus, larger radiators are needed for those locations
downstream in the loop. A common solution to this is
multiple loops or zones. Each zone has its own temperature control with circulation provided by a small pump or
zone valve in each loop. Two-pipe hydronic systems use a
pipe for supplying hot water to the radiators and a second
pipe for returning the water from the radiators to the
boiler.
There are also direct- and reverse-return arrangements.
The direct-return system can be difficult to balance
because the pressure drop through the nearest radiator
piping can be significantly less than for the farthest
radiator. Reverse-return systems take care of the balancing
problem, but require the expense of additional piping.
Orifice plates at radiator inlets or balancing valves at
radiator outlets can also be used to balance the pressure
drops in a direct-return system.
Direct Vent Wall Furnaces
Direct vent wall furnaces are specifically designed for
areas where flues or chimneys are not available or cannot
be used. The furnace is directly vented to the outside and
external air is used to support combustion. The air on the
inside is warmed as it recirculates around a sealed
chamber.
Cooling
Air Conditioning
Many old homes relied on passive cooling-opening windows and doors and using shading devices-during the
summer months. Homes were designed with windows on
opposite walls to encourage cross ventilation and large
12-15Chapter 12: Heating, Air Conditioning, and VentilatingHealthy Housing Reference Manual
shade trees reduced solar heat gains. This approach is still
viable, and improved thermal performance (insulating
value) windows are available that allow for larger window
areas to let in more air in the summer without the heat
loss penalty in the winter. However, increased outdoor
noise levels, pollution, and security issues make relying on
open windows a less attractive option in some locations
today.
An air conditioning system of some kind may be installed
in the home. It may be a window air conditioner or
through-the-wall unit for cooling one or two rooms, or a
central split-system air conditioner or heat pump. In any
event, the performance of these systems, in terms of providing adequate comfort without excessive energy use,
should be investigated. The age of the equipment alone
will provide some indication. If the existing system is
more than 10 years old, replacement should be considered because it is much less efficient than today’s systems
and nearing the end of its useful life.
The refrigerant commonly used in today’s residential air
conditioners is R-22. Because of the suspicion that R-22
depletes the ozone layer, manufacturers will be prohibited
from producing units with R-22 in 2010. The leading
replacements for R-22 are R-134A and R-410A, and new
products are now available with these nonozone-depleting
refrigerants.
The performance measure for electric air conditioners
with capacities less than 65,000 BTU is the seasonal
energy efficiency ratio (SEER). SEER is a rating of cooling performance based on representative residential loads.
It is reported in units of BTU of cooling per watt per
hour of electric energy consumption. It includes energy
used by the unit’s compressor, fans, and controls. The
higher the SEER, the more efficient the system. However,
the highest SEER unit may not provide the most comFigure 12.19. Location and Operation of Typical Backdraft Diverter [4]
fort. In humid climates, some of the highest SEER units
exhibit poor dehumidification capability because they
operate at higher evaporator temperatures to attain the
higher efficiency. A SEER of at least 10 is required by the
National Appliance Energy Conservation Act of 1987 for
conventional central split-system air-cooled systems. The
Department of Energy announced a SEER of 13 effective
January 2006.
Cooling system options vary widely, depending on the
level of control and comfort desired by the homeowner.
Fans can increase circulation and reduce cooling loads,
but they may be unsatisfactory in hot climates because
their cooling capability is directly limited by outdoor
conditions. Radiant barriers can reduce cooling loads in
very hot climates. Evaporative coolers can be a relatively
inexpensive and effective method of cooling in dry climates, such as the Southwest. Electric air conditioning
maintains a comfortable indoor temperature and humidity even under the most severe outdoor conditions. More
than 75% of new homes in the United States are
equipped with some form of central air conditioning:
50% of the homes in the Northeast, 75% in the
Midwest, 95% in the South, and approximately 60% in
the West. Electric air conditioning removes moisture
from the air and reduces its temperature. It can be a good
investment because, in most parts of the country, the payback is significant when the house is sold.
Electric air conditioners that use the vapor-compression,
refrigeration cycle are available in a variety of sizes and
configurations, ranging from small window units to large
central systems. The most common form of central air
conditioning is a split-system with a warm air furnace
(Figure 12.20). The same ductwork is used for distributing conditioned air during the heating and cooling seasons. Supply air is cooled and dehumidified as it passes
over an A-shaped evaporator coil. The liquid refrigerant
evaporates inside the coil as it absorbs heat from the air.
The refrigerant gas then travels through refrigerant piping
to the outdoor unit, where it is pressurized in an electrically driven compressor, raising its temperature and pressure, and returned to a liquid state in the condenser as it
releases, or dumps, the heat to the outdoors. A fan draws
outdoor air in over the condenser coil. The use of twospeed indoor fans can be advantageous in this type of
system because the cooling load often requires higher airflows than the heating load. The lower speed can be used
for the heating season and for improved dehumidification
performance during the cooling season. The condenser
unit for a house air conditioner is shown in Figure 12.21.
Healthy Housing Reference Manual12-16 Chapter 12: Heating, Air Conditioning, and Ventilating
Circulation Fans
Air movement can make a person feel comfortable even
when dry-bulb temperatures are elevated. A circulation
fan (ceiling or portable) that creates an airspeed of 150 to
200 feet per minute can compensate for a 4°F (-16°C)
increase in temperature.
Ceiling circulation fans also can be beneficial in the
heating season by redistributing warm air that collects
along the ceiling, but they can be noisy.
Evaporation Coolers
In dry climates, as in the southwestern United States, an
evaporative cooler or “swamp” cooler may provide sufficient cooling. This system cools an airstream by evaporating water into it; the airstream’s relative humidity
increases while the dry-bulb temperature decreases. A
95°F (35°C), 15% relative humidity airstream can be
conditioned to 75°F (24°C), 50% relative humidity. The
simplest direct systems are centrally located and use a
pump to supply water to a saturated pad over which the
supply air is blown. Indirect systems use a heat exchanger
between the airstream that is cooled by evaporating water
and the supply airstream. The moisture level of the supply airstream is not affected as it is cooled.
Evaporation coolers have lower installation and operating
costs than electric air conditioning. No ozone-depleting
refrigerant is involved. They provide high levels of ventilation because they typically condition and supply 100%
outside air.
Figure 12.20. Split-system Air Conditioner Figure 12.21. External Air-conditioning Condenser Unit
The disadvantages are that bacterial contamination can
result if not properly maintained and they are only appropriate for dry, hot climates.
Safety
Cooling homes with window air conditioners requires
attention to the maintenance requirements of the unit.
The filter must be cleaned or replaced as recommended
by the manufacturer, and the drip pan should be checked
to ensure that proper drainage from the unit is occurring.
The pans should be rinsed and disinfected as recommended by the manufacturer. Both bacteria and fungi
can establish themselves in these areas and present serious
health hazards.
Condensation forms on the cooling coils of central air
units inside and outside the home. These units should
have a properly installed drip pan and should be drained
according to the manufacturer’s instructions. They also
should receive routine maintenance, flushing, and disinfection. In the spring, before starting the air conditioner,
the unit should be checked by a professional or someone
familiar with the operation of the system. This is a good
time to check drip line(s) for conditions such as plugs,
cracks, or bacterial contamination because many of these
lines are plastic. The drip pan should be cleaned thoroughly and disinfected if necessary or replaced. A plugged
drip line can cause water damage by overflow from the
drip pan. In the fall, the heat unit also should be checked
before starting the system. Care should be taken with
both window air conditioning units and central air systems to use quality air filters that are designed for the
specific units and meet the specifications required by the
system’s manufacturer.
12-17Chapter 12: Heating, Air Conditioning, and VentilatingHealthy Housing Reference Manual
The housing inspector should be on the alert for
unvented, open flame heaters. Coil-type, wall-mounted
water heaters that do not have safety relief valves are not
permitted. Kerosene (portable) units for cooking or heating should be prohibited. Generally, open-flame portable
units are not allowed under fire safety regulations.
In oil heating units, other than integral tank units, the oil
must be filled and vented outside the building. Filling oil
within buildings is prohibited. Cutoff switches should be
close to the entry but outside of a boiler room.
Chimneys
Chimneys (Figure 12.22) are often an integral part of a
building. Masonry chimneys must be tight and sound;
flues should be terra cotta-lined; and, where no linings
are installed, the brick should be tight to permit proper
draft and elimination of combustion gases.
Chimneys that act as flues for gas-fired equipment must
be lined with either B vent or terra cotta. When a portion
of the chimney above the roof either loses insulation or
the insulation peels back, it indicates potential poisonous
gas release or water leakage problems and a need for
rebuilding. Exterior deterioration of the chimney, if
neglected too long, will permit erosion from within the
flues and eventually block the flue opening.
Rusted flashing at the roof level will also contribute to
the chimney’s deterioration. Efflorescence on the inside
wall of the chimney below the roof and on the outside of
the chimney, if exposed, will show salt accumulations— a
telltale sign of water penetration and flue gas escape and a
sign of chimney deterioration. During rainy seasons, if
terra cotta chimneys leak, dark areas show the number of
flues inside the masonry chimney so they can actually be
counted. When this condition occurs, it usually requires
2 or 3 months to dry out. After drying out, the mortar
joints are discolored (brown). After a few years of this
type of deterioration, the joints can be distinguished
whether the chimney is wet or dry. These conditions usually develop when coal is used and become more pronounced 2 to 5 years after conversion to oil or gas.
An unlined chimney can be checked for deterioration
below the roofline by looking for residue deposited at the
base of the chimney, usually accessible through a cleanout
(door or plug) or breaching. Red granular or fine powder
showing through coal or oil soot will generally indicate, if
in quantity (a handful), that deterioration is excessive and
repairs are needed.
Unlined chimneys with attached gas units will be devoid
of soot, but will usually show similar telltale brick powder Figure 12.22. Chimney Plan [4]
and deterioration. Manufactured gas has a greater tendency to dehydrate and decompose brick in chimney
flues than does natural gas. For gas installations in older
homes, utility companies usually specify chimney requirements before installation; therefore, older chimneys may
require the installation of terra cotta liners, nonlead-lined
copper liners, stainless steel liners, or transit pipe. Black
carbon deposits around the top of the chimney usually
indicate an oil burner operation using a low air ratio and
high oil consumption. Prolonged operation in this burner
setting results in long carbon water deposits down the
chimney for 4 to 6 feet or more and should indicate to
the inspector a possibility of poor burner maintenance.
This will accent the need to be more thorough on the
next inspection. This type of condition can result from
other causes, such as improper chimney height, or exterior obstructions, such as trees or buildings, that will
cause downdrafts or insufficient draft or contribute to a
faulty heating operation. Rust spots and soot-mold usually occur on deteriorated galvanized smoke pipe.
Fireplaces
Careful attention should be given to construction of the
fireplace (Figure 12.23). Improperly built fireplaces are a
serious safety and fire hazard. The most common causes
of fireplace fires are thin walls, combustible materials
such as studding or trim against sides and back of the
fireplace, wood mantels, and unsafe hearths.
Fireplace walls should be no less than 8 inches thick; if
built of stone or hollow masonry units, they should be no
less than 12 inches thick. The faces of all walls exposed to
fire should be lined with firebrick or other suitable fireresistant material. When the lining consists of 4 inches of
Healthy Housing Reference Manual12-18 Chapter 12: Heating, Air Conditioning, and Ventilating
firebrick, such lining thickness may be included in the
required minimum thickness of the wall.
The fireplace hearth should be constructed of brick,
stone, tile, or similar incombustible material and should
be supported on a fireproof slab or on a brick arch. The
hearth should extend at least 20 inches beyond the chimney breast and no less than 12 inches beyond each side of
the fireplace opening along the chimney breast. The combined thickness of the hearth and its supporting construction should be no less than 6 inches at any point.
It is important that all wooden beams, joists, and studs
are set off from the fireplace and chimney so that there is
no less than 2 inches of clearance between the wood
members and the sidewalls of the fireplace or chimney
and no less than 4 inches of clearance between wood
members and the back wall of the fireplace.
A gas-log set is primarily a decorative appliance. It
includes a grate holding ceramic logs, simulated embers, a
gas burner, and a variable flame controller. These sets can
Figure 12.23. Fireplace Construction [4]
be installed in most existing fireplaces. There are two
principal types: vented and unvented. Vented types
require a chimney flue for exhausting the gases. They are
only 20% to 30% efficient; and most codes require that
the flue be welded open, which results in an easy exit
path for heated room air. Unvented types operate like the
burner on a gas stove and the combustion products are
emitted into the room. They are more efficient because
no heat is lost up the flue and most are equipped with
oxygen-depletion sensors. However, unvented types are
banned in some states, including Massachusetts and
California. Gas fireplaces incorporate a gas-log set into a
complete firebox unit with a glass door. Some have builtin dampers, smoke shelves, and heat-circulating features
that allow them to provide both radiant and convective
heat. Units can have push-button ignition, remote control, variable heat controls, and thermostats. Gas fireplaces are more efficient than gas logs, with efficiencies of
60% to 80%. Many draw combustion air in from the
outside and are direct vented, eliminating the need for a
chimney. Some of these units are wall-furnace rated.
There are also electric fireplaces that provide the ambience of a fire and, if desired, a small amount of resistance
heat. These units have no venting requirements. The
advantages are that there are no ashes or flying sparks that
occur with wood-burning fireplaces. They are not affected
by wood-burning bans imposed in some areas when air
quality standards are not met. Direct-vented gas or electric models eliminate the need for a chimney.
The disadvantages are that the cost for equipment and
running the gas line can be high.
References
1. US Census Bureau. Rooms, number of bedrooms, and
house heating fuel: 2000. Census 2000 Summary File 4
(SF4). Washington, DC: US Census Bureau; 2000.
Available from URL: http://factfinder.census.gov
[select Data Sets, then select Census 2000 Summary
File 4 (SF 4) - Sample Data].
2. National Energy Efficiency Committee. Building: heat
pumps; application of heat pumps in Singapore.
Singapore: National Environment Agency; 2003.
Available from URL: http://www.neec.gov.sg/building/
heat_pump.shtm.
3. National Energy Efficiency Committee. Renewables:
solar energy. Singapore: National Environment Agency;
no date. Available from URL: http://www.neec.gov.sg/
renewables/solar.shtm.
12-19Chapter 12: Heating, Air Conditioning, and VentilatingHealthy Housing Reference Manual
4. Center for Disease Control. Basic housing inspection.
Atlanta: US Department of Health and Human Services;
1976.
5. Fairfax County. Fuel storage tanks. Fairfax, VA: Fairfax
County; 2004. Available from URL: http://www.co.
fairfax.va.us/dpwes/construction/fuel_tanks.htm.
6. Wisconsin Department of Commerce. Environmental
services— residential fuel oil and gasoline storage tanks.
Madison, WI: Wisconsin Department of Commerce;
2004. Available from URL: http://www.commerce.state.
wi.us/ER/ER-BST-ResTk.html.
7. Michigan Department of Environmental Quality. FAQ:
Home heating oil tanks, Lansing, MI: Michigan
Department of Environmental Quality; no date. Available
from URL: http://www.michigan.gov/deq/0,1607,7-1353311_4115_4238-9379--,00.html.
8. US Environmental Protection Agency. Overview of the
federal underground storage tank program. Washington,
DC: U.S. Environmental Protection Agency; no date.
Available from URL: http://www.epa.gov/swerust1/
overview.htm.
9. US Department of Housing and Urban Development.
Initiatives Programs. Washington, DC: US Department of
Housing and Urban Development; 2004. Available from
URL: http://www.hud.gov/offices/cpd/energyenviron/
energy/initiatives.
10. US Environmental Protection Agency. Sources of indoor
air pollution— asbestos. Washington, DC: U.S.
Environmental Protection Agency; no date. Available from
URL: http://www.epa.gov/iaq/asbestos.html.
11. The Commonwealth of Massachusetts Board of Building
Regulations and Standards (BBRS). Hydronic system
requirements. Boston: The Commonwealth of
Massachusetts Board of Building Regulations and
Standards (BBRS); no date. Available from URL:
http://www.mass.gov/bbrs/commntry/cmpxhydr.htm.
Additional Sources of Information
McQuiston FC, Parker JD, Spitler JD. Heating, ventilation, and air conditioning: analysis and design. 5th ed.
Hoboken, NJ: John Wiley and Sons, Inc.; 2000.
Kittle JL. Home heating and air conditioning systems.
New York: McGraw-Hill; 1990.
Pita EG. Air conditioning principles and systems: an
energy approach. 4th ed. New York: Prentice Hall; 2001.
Healthy Housing Reference Manual12-20 Chapter 12: Heating, Air Conditioning, and Ventilating
13-1Chapter 13: Energy EfficiencyHealthy Housing Reference Manual
“Engineering is the science of economy, of conserving the
energy, kinetic and potential, provided and stored up by
nature for the use of man. It is the business of engineering to
utilize this energy to the best advantage, so that there may be
the least possible waste.”
William A. Smith
1908
Introduction
Using energy efficiently can reduce the cost of heating,
ventilating, and air-conditioning, which account for a significant part of the overall cost of housing. Energy costs
recur month-to-month and are hard to reduce after a
home has been designed and built. The development of
an energy-efficient home or building must be thought
through using a systems approach. Planning for energy
efficiency involves considering where the air is coming
from, how it is treated, and where it is desired in the
home. Improper use or installation of sealing and insulating materials may lead to moisture saturation or retention, encouraging the growth of mold, bacteria, and
viruses. In addition, toxic chemicals may be created or
contained within the living environment. These building
errors may result in major health hazards. The major
issues that must be balanced in using a systems approach
to energy efficiency are energy cost and availability, longterm affordability and sustainability, comfort and efficiency, and health and safety.
Energy Systems
Making sound decisions in designing, constructing, or
updating dwellings will ensure not only greater use and
enjoyment of the space, but also can significantly lower
energy bills and help residents avoid adverse health
effects. Systematic planning for energy efficiency also can
assist prospective homeowners in qualifying for mortgages
because lower fuel bills translate into lower total housing
and utility payments. Some banks and credit unions take
this into account when qualifying prospective homeowners for mortgages. “Energy-efficient” mortgages provide
buyers with special benefits when purchasing an energyefficient home.
Energy use and efficiency should be addressed in the context of selection of fuel types and appliances, location of
the equipment, equipment sizing and backup systems,
and programmed use when making decisions on space
Chapter 13: Energy Efficiency
heating, water heating, space cooling, window glazing,
and lighting. Usage variables, such as taking excessively
long showers, turning off lights when leaving rooms, or
using appliances at full or near-full capacity, may increase
or decrease energy use, depending on occupancy. Many of
these demands can be optimized in the design stage of
housing for new construction. However, when remodeling dwellings, making modifications to improve energy
efficiency is often difficult. Preconstruction consultations
with architects and energy specialists can produce tradeoffs that retain the aesthetics and special aspects of a
dwelling, while making appropriate investments in energy
efficiency.
A price is paid for poor design and lack of proper insulation of dwellings, both in dollars for utility bills and in
comfort of the occupants. The layout of rooms and overall tightness of a house in terms of air exchange affect
energy requirements. In addition, home occupants and
owners often are called on to make relatively minor decisions affecting total energy consumption, such as selecting lighting fixtures and bulbs and selecting settings for
thermostats. Buying energy-efficient appliances can save
energy, but the largest reduction in energy use can be
derived from major decisions, such as considering the
R-value of roof systems, insulation, and windows.
R-values
Thermal resistance (a material’s resistance to heat flow) is
rated by R-value. Higher R values mean greater insulating
power, which means greater household energy savings and
commensurate cost savings. Table 13.1 is a guideline for
choosing R-values that are right for a particular home
based on the climate, household heating system, and area
in which it is located.
Another way of understanding R-value is to see it as the
resistance to heat losses from a warmer inside temperature
to the outside temperature through a material or building
envelope (wall, ceiling or roof assembly, or window).
Total heat loss is a function of the thermal conductivity
of materials, area, time, and construction in a house.
The R-value of thermal insulation depends on the type of
material, its thickness, and its density. In calculating the
R-value of a multilayered installation, the R-values of the
individual layers are added. Installing more insulation
increases R-value and the resistance to heat flow.
Healthy Housing Reference Manual13-2 Chapter 13: Energy Efficiency
The effectiveness of an insulated wall or ceiling also
depends on how and where the insulation is installed. For
example, insulation that is compressed will not provide its
full rated R-value. Also, the overall R-value of a wall or
ceiling will be somewhat different from the R-value of the
insulation itself because some heat flows around the insulation through the studs and joists. That is, the overall
R-value of a wall with insulation between wood studs is
less than the R-value of the insulation itself because the
wood provides a thermal short-circuit around the insulation. The short-circuiting through metal framing is much
greater than that through wood-framed walls; sometimes
the metal wall’s overall R-value can be as low as half the
insulation’s R-value. With careful design, this short-circuiting can be reduced.
Roofs
Roofs are composite structures, with composite R-values.
The total R-value for the roof components shown in
Figure 13.1 is 14.54 (Table 13.2). In general, a composite
structure with a composite R-value of more than R-38
In a climate that is…
And a heating system
that is… [b]
Insulate to these levels in the… Ducts [e] in
unheated/uncooled…
Ceiling
Woodframe
wall [c] Floor
Basement
or crawl
space walls
[d] Attic
Basement or
crawl space
Warm, with cooling and minimal
heating requirements [f]
Gas/oil or
heat pump
R-22 to
R-38
R-11 to
R-15
R-11 to
R-13
R-11 to
R-19
R-4 to
R-8 None to R-4
Electric
resistance
R-38 to
R-49
R-11 to
R-22
R-13 to
R-25
R-11 to
R-19
R-4 to
R-8 None to R-4
Gas/oil or
heat pump R-38
R-11 to
R-22
R-13 to
R-25
R-11 to
R-19
R-4 to
R-8 R-2 to R-8
Mixed, with moderate heating
and cooling requirements [g]
Electric
resistance R-49 R-11 to R-28 R-25
R-11 to
R-19
R-4 to
R-8 R-2 to R-8
Cold, with mainly heating
requirements [h]
Gas/oil R-38 to
R-49
R-11 to
R-22 R-25
R-11 to
R-19
R-6 to
R-11 R-2 to R-11
Heat pump
or electric
resistance
R-49 R-11 to R-28 R-25
R-13 to
R-19
R-6 to
R-11 R-2 to R-11
a. Adapted from the U.S. Department of Energy 1997 Insulation Fact Sheet available at (800)-DOE-EREC and Modera et al., Impact of Residential Duct
Insulation on HVAC Energy Use and Life Cycle Cost to Consumers, ASHRAE Transactions 96-13-4.
b. Insulation is also effective at reducing cooling bills. These levels assume your house has electric air conditioning.
c. R-values may be achieved through a combination of cavity insulation and rigid board insulation and are for insulation only (not whole wall).
d. Do not insulate crawl space walls if crawl space is wet or ventilated with outdoor air.
e. Use the lower R-value for return ducts and higher R-value for supply ducts.
f. Florida and Hawaii; coastal California; southeast Texas; southern Alabama, Arkansas, Georgia, Louisiana, and Mississippi.
g. Idaho, Kentucky, Missouri, Nebraska, Oklahoma, Oregon, Virginia, Washington, and West Virginia; southern Indiana, Kansas, New Mexico, and Arizona;
northern Alabama, Arkansas, Georgia, Louisiana, and Mississippi; inland California; and western Nevada.
h. Great Lakes area, mountainous areas [e.g., Colorado, Wyoming, Utah, etc.]), New England, New York, northern Midwest, and Pennsylvania.
Table 13.1. Cost-effective Insulation R-values for Existing Homes [a;1]
provides a substantial barrier to heat loss. Of course, in the
winter the outside air temperature would vary significantly
between locations such as Pensacola, Florida, and
Fairbanks, Alaska, and would affect the cost-effectiveness
of additional insulation and construction using various
roofing components (Table 13.2).
The location of a house is usually a fixed variable in
calculating R-values once the lot is purchased. However,
the homeowner should consider the value of additional
insulation by comparing its cost with the savings resulting
from the increase in energy efficiency. Roof construction,
including components such as ridge vents and insulating
materials, is quite important and is often one of the more
cost-effective ways to lower energy costs.
Ridge Vents
Ridge vents are important to roofs for at least three reasons. First, ridge vents help lower the temperature in the
roof structure and, consequently, in the attic and in the
habitable space below. Second, ridge vents and rotating
turbine vents help prolong the life of the roofing materials,
13-3Chapter 13: Energy EfficiencyHealthy Housing Reference Manual
particularly asphalt shingles and plywood sheathing.
Third, ridge vents assist in air circulation and help avoid
problems with excessive moisture.
Fan-powered Attic Ventilation
Attic ventilators are small fans that remove hot air and
reduce attic temperature. Adequate inlet vents are
important. Typically these vents are located under the
eaves of the house. The fan should be located near the
peak of the roof for best performance.
White Roof Surface
White roof surfaces combined with any of the measures
listed above will improve their performance significantly.
The white surface reflects much of the sun’s heat and
keeps the roof much cooler than a typical roof.
Insulation
Insulation forms a barrier to the outside elements. It can
help ensure that occupants are comfortable and that the
home is energy-efficient. Ceiling insulation improves
comfort and cuts electricity or natural gas costs for
heating and cooling. For instance, the use of R-19
insulation in houses in Hawaii [3] could have the
following results:
• Reduce indoor air temperature by 4°F (-16°C) in the
afternoon.
Figure 13.1. Roof Components [2]
Component R-value
Inside air film 0.92
Steel deck 0.00
2-inch polyisocyanurate (5.56 x 2) 11.12
¾-inch perlite (2.78 x 0.75) 2.09
Smooth built-up roof 0.24
Outside air film in winter 0.17
Total 14.54
Table 13.2. Potential Effects of Radiant Barriers [3]
• Lower the ceiling temperature, perhaps by more than
15°F (-9.4°C). Insulation [radiant barrier] can reduce
ceiling temperatures from 101°F (38°C) in bright sun
on Oahu to 83°F (28°C). (Figure 13.2).
• Reduce or eliminate the need for an air-conditioner.
Energy savings, of course, will vary depending on energy
prices. The payback afforded by additional insulation or
investment in energy conservation measures is the average
amount of time it will require for the initial capital cost
to be recovered as a result of the savings in energy bills. A
payback of 3 to 5 years might be economic, because the
average homeowner stays in a home that long. However,
payback criteria can vary by individual, and renters, for
example, often face the dilemma of not wanting to make
improvements for which they may not be able to fully
realize the benefits. Described below are a few insulation
alternatives.
To achieve maximum effect, the method of installation
and type of insulation are of considerable importance.
The proper placement of moisture barriers is essential. If
insulation becomes moisture-saturated, its resistance to
energy loss is significantly reduced. Barriers to moisture
should be installed toward the living area because significant moisture is generated in the home through respiration, cooking, and the combustion of heating fuels.
Cellulose or fiberglass insulation is the most cost-effective insulation. Blown-in cellulose or fiberglass and fiberglass batts are similar in cost and performance. Recycled
cellulose insulation may be available. For the best performance, insulation should be 5 to 6 inches thick. It can be
installed in attics of new and existing homes. It is typically the best choice for framed ceilings in new homes,
but can be costly to install in existing framed ceilings. It
is very important that this type of insulation be treated
for fire resistance.
Foamboard (R-10, 1.5 to 2 inches) provides more insulation per inch than does cellulose or fiberglass, but is also
more expensive. It is best where other insulation cannot
be used, such as open-beam ceilings. It is applicable for
new construction or when roofing is replaced on an existing home. Two common materials are polystyrene and
polyisocyanurate. Polystyrene is better in moist conditions, and polyisocyanurate has a higher R-value per inch.
However, some of these insulations present serious fire
spread hazards. They should be evaluated to ensure that
they are covered with fire-retardant materials and meet
local fire and building codes.
Healthy Housing Reference Manual13-4 Chapter 13: Energy Efficiency
Radiant barrier insulation is a reflective foil sheet
installed under the roof deck like regular roof sheathing.
The effectiveness of a radiant barrier (Figure 13.2)
depends on its emissivity (the relative power of the surface to emit heat by radiation). In general, the shinier the
foil the better. Radiant barrier insulation cuts the amount
of heat radiated from the hot roof to the ceiling below. It
may be draped over the rafters before the roof is installed
or stapled to the underside of the rafters. The shiny side
should face downward for best performance. Some manufacturers claim that the radiant barrier prevents up to
97% of the sun’s heat from entering the attic.
Wall Insulation
As shown in Table 13.1, it makes sense to insulate to high
R-values in the ceiling. Insulation in walls should range
from R-11 in relatively mild climate zones to R-38 in
New England, the northern Midwest, the Great Lakes,
and the Rocky Mountain states of Colorado and Wyoming.
Insulation requirements vary within climate zones in
these states and areas as well (for instance, mountainous
areas and areas farther north may have more
heating-degree days). The same logic of installing
insulation applies to both ceilings and walls: the
insulation should provide a barrier for heat and moisture
transfer and buildup from inside the dwelling, where
temperatures will generally be in the 68°F to 72°F (20°C
to 22°C) range, compared with the much colder or hotter
temperatures outside. The key to heat loss is the
difference in temperatures and the time that the heat
transfer takes place over a given area or surface. The
choice of heating system, from gas/oil or heat pump, to
electric resistance, will also affect the payback of
Figure 13.2. Potential Effects of Radiant Barriers [3]
additional wall insulation due to variation in energy fuel
prices. For regions identified as “cold,” careful attention
should be made in selecting energy fuel type; in
particular, a heat pump may not be a practical option.
A homeowner exploring designs and construction methods should examine the value of using structural insulated
panels. The incorporation of high levels of insulation
directly from the factory on building wall and ceiling
components makes them outstanding barriers to heat and
moisture. These integrated systems, if appropriately used,
can save substantial amounts of energy when compared
with traditional stick-built systems using 2×4 or 2×6 lumber. Also, building energy-efficient features (as well as
electrical, plumbing, and other elements) directly into the
building envelope at the factory can result in labor cost
savings over the more traditional methods of
construction.
Floor Insulation
Warm air expands and rises above surrounding cooler air.
This process of heat transfer is called convection. Warm
air, which is lighter, rises and, as it cools, falls, creating a
convection current of air. The two other processes of heat
transfer are conduction (kinetic energy transferred from
particle to particle, such as in a water- or electrically
heated floor) and radiation (radiant energy emitted in the
form of waves or particles such as in a fireplace or hot
glowing heating element). Floor insulation limits all three
modes of heat loss. A warmer floor reduces the temperature
difference that drives convection. Floor insulation also
directly impedes conduction and radiation to the colder
air below the floor.
Batt Insulation
The advantage of floor insulation lies in adding extra
R-value without a significant increase in cost. It is
cheaper to put more insulation under the floor than to
add foam sheathing or change the type of wall construction to accommodate greater insulation levels.
Like walls, floor cavities should be completely filled with
insulation-without gaps, missing insulation, or cavity
voids. Floor insulation must contact the subfloor and
both joists. In many cases, it is worth the extra cost to
buy enough insulation to fill the entire cavity.
The amount of floor insulation required by some codes
can be less than the space available. For example, an R-19
fiberglass batt is 6¼ inches thick. A floor framed with
2×8s is about 7½ inches deep, while a 2×10 floor is 9½
inches deep. A builder following a code’s minimum insulation level will leave extra space that will allow for greater
13-5Chapter 13: Energy EfficiencyHealthy Housing Reference Manual
In some areas, it’s common to hang plastic mesh over
floor joists. Installers drop the insulation onto the mesh
before the subfloor is installed. However, hanging the
mesh creates sagging bellies. Insulation compresses near
the framing and sags in the middle. Mesh should be
attached to the bottom of the floor framing [4].
Each stage of increased floor insulation, from R-19 to
R-30 or R-30 to R-38, can save energy over the life of the
house. This energy translates into energy savings that are
multiples of the initial installation costs. Floor insulation
will generate the greatest savings in colder climates; in
moderate climates, the target insulation level should
depend on economics.
Blow-In Insulation
A blown-in insulation system allows the builder or insulator to fill the entire cavity completely, even around pipes,
wires and other appurtenances. Using well-trained installers will pay dividends in quality workmanship.
Doors
Today there is an endless variety of doors, ranging from
metal doors with or without insulation to hollow core to
solid wood. When properly installed into fitted frames,
doors serve as a heat barrier to maintain indoor temperatures. Quality metal doors with insulation are best if they
have a thermal break between the interior and exterior
metal surfaces; this keeps heat from being transferred
from one side to the other.
Standard Doors
Because doors take up a small percentage of a wall,
insulating them is not as high a priority as is insulating
walls and ceilings. That said, heat loss follows the path of
least resistance; therefore, doors should be selected that
are functional and add to the energy-efficiency of the
house. Doors usually have lower R-values than the
surrounding wall.
Storm doors can add R-1 to R-2 to the existing door’s
R-value. They are a valuable addition to doors that are
frequently used and those that are exposed to cold winds,
snow, and other weather. Screens allow natural breezes to
circulate air from outside, rather than totally relying on
air-conditioning, which can be energy intensive.
When considering replacement doors, select insulated,
metal foam-core doors. Besides insulation, metal doors
provide good security, seal more tightly, tend to warp less.
Metal doors also are more soundproof than conventional
wood doors.
heat loss. To avoid this
situation, the batt must
be pushed up into the
cavity. With the proper
support, this can be
done. Springy metal
rods are commonly used
to hold insulation up in
the top of the floor cavity. Another viable
option is the use of plastic straps. Figure 13.3
shows batt insulation
improperly applied to
the floor above a crawl space or a basement.
The thickness of typical fiberglass batts can assist the
designer and the builder in creating a floor system that
works for the occupants. Table 13.3 shows a list of
R-values, along with the associated batt thickness.
Individual brands can vary by as much as 1 inch.
Cavity Fill
According to Oikos, a commercial Web site devoted to
serving professionals whose work promotes sustainable
design and construction, “Buying a thicker batt may be a
better option than trying to lift a thinner batt into the
proper position. Material costs will climb slightly but
labor should be the same. Attaching the insulation support to the bottom of the floor joist will be easier. It
could also lead to a higher quality job because there is less
chance for compression or gaps” (Figure 13.4) [4].
Figure 13.3. Common Floor Insulation Flaws [4.] Two common flaws in
floor insulation are gaps above the batt and compression of the batt in
the cavity.
Source: Reprinted from Energy Source Builder 38 with permission of Iris
Communications, Inc., publisher of Oikos.com.
R-value
Batt Thickness,
Inches
R-19 6¼
R-22 HD 5½
R-22 7½
R-25 8½
R-30 10
R-30 HD 8½
R-38 12
R-38 HD 10
Table 13.3. Floor Insulation [5]
Healthy Housing Reference Manual13-6 Chapter 13: Energy Efficiency
Sliding Glass Doors
Although sliding glass doors have aesthetic appeal, they
have very low R-values and hence are minimally energy
efficient. To improve the energy efficiency of existing sliding glass doors, the homeowner should ensure that they
seal tightly and are properly weather-stripped.
Additionally, heavy insulated drapes with weights, which
impede the airflow, can cut down on heat loss through
sliding glass doors.
Door Installation
Doors must be installed as recommended by the manufacturer. Care must be taken to be sure that doors are
Figure 13.4a. Insulation Cavity Fill [4].
Lath provides a sturdy support for insulation.
Figure 13.4b. Insulation Cavity Fill [4].
Metal rods are available through insulation distributors. They are easy to
use, but insulation has to be compressed in the middle.
Figure 13.4c. Insulation Cavity Fill [4].
Mesh should be attached to the bottom of the framing. Draping the
mesh over the joists leads to compression that reduces insulating value.
Figure 13.4d. Insulation Cavity Fill [4].
Polypropylene twine resists rot, mildew, rodents, and other dangers. It is
to be stapled every 12 to 18 inches.
Source: Reprinted from Energy Source Builder 38 with permission of Iris Communications, Inc., publisher of Oikos.com.
installed in a manner that does not trap moisture or allow
unintended introduction of air. Numerous types of sealing
materials are available that range from foam to plastic, to
metal flanging and magnetic strips.
Hot Water Systems
The hot water tank can be insulated to make it more efficient, unless the heat loss is used within the space where it
is located. Special insulation is available for this type of
appliance, and insulating it will reduce the energy required
to deliver the hot water needed by the occupants of the
dwelling. Of course, any pipe that is subject to extreme
temperatures also should be insulated to decrease heat loss.
13-7Chapter 13: Energy EfficiencyHealthy Housing Reference Manual
Windows
Windows by nature are transparent. They allow occupants of a dwelling to see outside and bring in sunlight
and heat from the sun. They make space more pleasant
and often provide lighting for tasks undertaken in the
space. Especially in the winter, these desirable characteristics offset the heat loss. Heat gain in the summer through
windows can be undesirable.
Rather than give them up, it is important to use windows
prudently and to keep energy considerations in mind in
their design and their insulating characteristics (air, glass,
plastic, or gas filler). Good design takes advantage of day
lighting. Weather-stripping and sealing leaks around windows can enhance comfort and energy savings. Energy
Star windows are highly recommended. Housekeeping
measures can improve the efficiency of retaining heat.
Heat loss follows the path of least resistance: caulking,
weather-stripped framing, and films can help. These measures are relatively labor intensive, low to very low in cost,
and can be quite satisfying to the homeowner if accomplished correctly. On the other hand, it is not easy finding the perfect materials or even replacement parts for old
windows.
When working with older windows, remember that there
is the risk for leaded paint and the dispersion of toxic
lead dust into the work area. Please refer to the lead section of Chapter 5, Indoor Air Pollutants and Toxic
Materials.
Caulking and Weather-Stripping
According to the U.S. Department of Energy, caulking
and weather-stripping have substantial housekeeping
benefits in preventing energy loss or unwanted heat gain.
Caulking
Caulks are airtight compounds (usually latex or silicone)
that fill cracks and holes. Before applying new caulk, old
caulk or paint residue remaining around a window should
be removed using a putty knife, stiff brush, or special solvent. After old caulk is removed, new caulk can then be
applied to all joints in the window frame and the joint
between the frame and the wall. The best time to apply
caulk is during dry weather when the outdoor temperature is above 45°F (7.2°C). Low humidity is important
during application to prevent cracks from swelling with
moisture. Warm temperatures are also necessary so the
caulk will set properly and adhere to the surface [5].
Weather-stripping
Weather-stripped frames are narrow pieces of metal,
vinyl, rubber, felt, or foam that seal the contact area
between the fixed and movable sections of a window
joint. They should be applied between the sash and the
frame, but should not interfere with the operation of the
window [6].
Replacing Window Frames
The heat-loss characteristics and the air tightness of a
window vary with the type and quality of the window
frame. The types of available window frames are fixedpane, casement, double- and single-hung, horizontal sliding, hopper, and awning. Each type varies in energy
efficiency.
Correctly installed fixed-pane windows are the most airtight and inexpensive choice, but are not suited to places
that require ventilation. The air infiltration properties of
casement windows (which open sideways with hand
cranks), awning windows (which are similar to casement
windows but have hinges at the top), and hopper windows (inverted awning windows with hinges at the bottom) are moderate. Double-hung windows, which have
top and bottom sashes (the part of the window that can
slide), tend to be leaky. The advantage of the single-hung
window over the double-hung is that it tends to restrict
air leakage because there is only one moving part.
Horizontal sliding windows, though suitable for small,
narrow spaces, provide minimal ventilation and are the
least airtight.
In buildings with large older windows, there are often
weight cavity areas that hide counter balances that make
it easy to raise and lower heavy windows. These areas
should be insulated to reduce energy loss.
Tinted Windows
Another way to conserve energy is the installation of
tinted windows. Window tinting can be installed that will
both conserve energy and also prevent damaging ultraviolet light from entering the room and potentially fading
wood surfaces, fabrics, and carpeting. Low-emissivity
coatings, called low-e coatings, are also available. These
coatings are designed for specific geographic regions.
Reducing Heat Loss and Condensation
The energy efficiency of windows is measured in terms of
their U-values (measure of the conductance of heat) or
their R-values. Besides a few highly energy-efficient
Healthy Housing Reference Manual13-8 Chapter 13: Energy Efficiency
exceptions, window R-values range from 0.9 to 3.0.
When comparing different windows, it is advisable to
focus on the following guidance for R- and U-values:
• R- and U-values are based on standards set by the
American Society of Heating, Refrigerating, and AirConditioning Engineers [7].
• R- and U-values are calculated for the entire window,
which includes the frame.
• R- and U-values represent the same style and size of
windows.
The R-value of a window in an actual house is affected by
the type of glazing material, the number of layers of glass,
the amount of space between layers and the nature of the
gas filling them, the heat-conducting properties of the
frame and spacer materials, and the airtightness associated
with manufacturing.
For windows, rating and approval by the National
Fenestration Rating Council or equivalent rating and
approval is strongly recommended [8].
Please refer to the window section of Chapter 6, Housing
Structure.
Glazing
Glazing refers to cutting and fitting windowpanes into
frames. Glass has been traditionally the material of choice
for windowpanes, but that is changing. Several new materials are available that can increase the energy efficiency of
windows. These include the following:
• Low-emissivity (low-e) glass uses a surface coating to
minimize transmission of heat through the window by
reflecting 40% to 70% of incident heat while letting
full light pass through the pane.
• Heat-absorbing glass is specially tinted to absorb
approximately 45% of the incoming solar energy;
some of this energy passes through the pane.
• Reflective glass has a reflective film that reduces heat
gain by reflecting most of the incident solar radiation.
• Plastic glazing materials such as acrylic,
polycarbonate, polyester, polyvinyl fluoride, and
polyethylene are stronger, lighter, cheaper, and easier to
cut than glass. However, they are less durable and tend
to be affected by the weather more than glass is.
• Storm windows can improve the energy efficiency of
single-pane windows. The simplest example of storm
windows would be plastic film, available in
prepackaged kits, taped to the inside of the window
frame. Because this can affect visibility and be easily
damaged, a better choice would be to attach rigid or
semirigid plastic sheets such as plexiglass, acrylic,
polycarbonate, or fiber-reinforced polyester directly to
the window frame or mounting it in channels around
the frame on the outside of the building. Care should
be taken in installation to avoid ripples or blemishes
that will affect visibility.
Layering
The insulating capacity of single-pane windows is minimal,
around R-1. Multiple layers of glass can be used to increase
the energy efficiency of windows. Double- or triple-pane
windows have air-filled or gas-filled spaces, coupled with
multiple panes that resist heat flow. The space between
the panes is critical because the air spaces that are too
wide (more than 5/8 inch) or too narrow (less than ½ inch)
allow excessive heat transfer. Modern windows use inert
gases, such as argon and krypton, to fill the spaces
between panes because these gases are much more
resistant to heat flow than air is. These gas-filled
windows are more expensive than regular double-pane
windows.
• Frame and spacer materials may be aluminum,
wood, vinyl, fiberglass, or a combination of these
materials, such as vinyl- or aluminum-clad wood.
• Aluminum frames are strong and are ideal for
customized window design, but they conduct heat
and are prone to condensation. The deterioration of
these frames can be avoided by anodizing or coating.
Their thermal resistance can be boosted using
continuous strips of plastic between the interior and
exterior of the frame.
• Wood frames are superior to aluminum frames in
having higher R-values, tolerance to temperature
extremes, and resistance to condensation. On the
other hand, wood frames require considerable
maintenance in the form of painting or staining.
Improper maintenance can lead to rot or warping.
• Vinyl window frames made from polyvinyl chloride
are available in a wide range of styles and shapes, can
be easily customized, have moderate R-values, and can
be competitively priced. Large windows made of vinyl
frames are reinforced using aluminum or steel bars.
Vinyl windows should be selected only after
consideration of the concerns surrounding the use of
vinyl materials and their off-gassing characteristics.
13-9Chapter 13: Energy EfficiencyHealthy Housing Reference Manual
• Fiberglass frames have the highest R-values and are
not given to warping, shrinking, swelling, rotting, or
corroding. Fiberglass is not weather-resistant, so it
should also be painted. Some fiberglass frames are
hollow; others are filled with fiberglass insulation.
• Spacers separating multiple windowpanes in a
window use aluminum to separate glass in multipane
windows, but it conducts heat. In addition, in cold
weather, the thermal resistance around the edge of
such a window is lower than that in the center,
allowing heat to escape and condensation to occur
along the edges.
• Polyvinyl chloride foam separators placed along the
edges of the frame reduce heat loss and condensation.
Window manufacturers use foam separators, nylon
spacers, and insulation materials such as polystyrene
and rock wool insulation between the glass panes
inside windows.
Other Options
Shades, shutters, and drapes used on windows inside the
house reduce heat loss in the winter and heat gain in the
summer. The heat gain during summer can also be minimized
by the use of awnings, exterior shutters, or screens. These
cost-effective window treatments should be considered before
deciding on window replacement. By considering orientation,
day lighting, storage of or reflection of energy from
sunshine, and materials used within the house and on the
building envelope, heat loss and gain can be decreased.
Solar Energy
Solar energy is a form of renewable energy available to
homeowners for heating, cooling, and lighting. The more
energy-efficient new structures are designed to store solar
energy. Remodeled structures may be retrofitted to
increase energy efficiency by improving insulation characteristics, improving airflow and airtightness of the structure, and enhancing the ability to use solar energy. Solar
energy systems are active and passive. Whereas active solar
systems use some type of mechanical power to collect,
store, and distribute the sun’s energy, passive systems use
the materials and design elements in the structure itself.
Active Solar Systems
Active solar systems use devices to collect, convert, and
deliver solar energy. Solar collectors on roofs or other
south-facing surfaces can be used to heat water and air
and generate electricity. Active solar systems can be
installed in new or existing buildings and periodically
need to be inspected and maintained. Active solar energy Figure 13.5. Solar Panels
equipment consists of collectors, a storage tank, piping
or ductwork, fans, motors, and other hardware. Flat
panel collectors (Figure 13.5) can be placed on the roof
or on walls. Typically, the collector will be a sandwich of
one or two sheets of glass or plastic and another air
space above a metal absorber plate, which is painted
black to enhance heat absorption. After collection, when
the sun’s energy is converted to heat, a transfer is made
to a liquid storage tank. The heated liquid travels
through coils in the hot water tank, and the heat is
transferred to the water and perhaps the heating system.
Most hot water systems use a liquid collector system
because it is more efficient and less costly than an airtype system.
In the southwest United States, solar roof ponds have
become popular for solar cooling. Evaporative cooling
systems depend on water vaporization to lower the temperature of the air. These have been shown to be more
effective in dry climates than in areas with extremely
high relative humidity.
In certain climates, like those in the Hawaiian Islands,
using solar energy is cost-effective for providing hot
water. Some builders even include it as a standard feature in their homes. The total cost to the homeowner of
solar energy systems consists of the capital, operational,
and maintenance costs. The real cost of capital may be
lowered by the availability of tax credits offered at the
federal (to lower federal income taxes) and state levels.
Homeowners and builders can benefit from tax credits
because they lower the total upfront investment cost of
installing active solar systems. This is the major portion
of the total cost of using solar energy, because operation
and maintenance costs are small in comparison to initial
system costs.
Passive Solar Systems
Buildings designed to use passive solar energy have features incorporated into their design that absorb and
slowly release the sun’s heat. In cold climates, the design
allows the light and heat of the sun to be stored in the
Healthy Housing Reference Manual13-10 Chapter 13: Energy Efficiency
structure, while insulating against the cold. In warm
climates, the best effect is achieved by admitting light
while rejecting heat. A building using passive solar systems may have the following features in the floor plan:
• Large south-facing windows
• Small windows in other directions, particularly on the
north side of the structure
• Designs that allow daylight and solar heat to permeate
the main living areas
• Special glass to block ultraviolet radiation
• Building materials that absorb and slowly reradiate the
solar heat
• Structural features such as overhangs, baffles, and
summer shading to eliminate summer overheating.
Passive design can be a direct-gain system when the sun
shines directly into the building, thereby heating it and
storing this heat in the building materials (concrete, stone
floor slabs, and masonry partitions). Alternatively, it may
be an indirect gain system where the thermal mass is
located between the sun and the living space. Isolated
gain is yet another type of system that is separated from
the main living area (such as a sunroom or a solar
greenhouse), with convective loops for space conditioning
into the living space.
Energy Star is a program supported and promoted by the
U.S. Environmental Protection Agency (EPA) that helps
individuals protect the environment through superior
energy efficiency. For the individual in his or her home,
energy-efficient choices can save families about one third
on their energy bill, with similar savings of greenhouse
gas emissions, without sacrificing features, style, or
comfort. When replacing household products, look for
ones that have earned the Energy Star; these products
meet strict energy-efficiency guidelines set by EPA and
the U.S. Department of Energy. When looking for a new
home, look for one that has earned the Energy Star
approval. If you are planning to make larger
improvements to your home, EPA offers tools and
resources to help you plan and undertake projects to
reduce your energy bills and improve home comfort [9].
In 2004 alone, Americans, with the help of Energy Star,
saved enough energy to power 24 million homes and
avoid greenhouse gas emissions equivalent to those from
20 million cars-all while saving $10 billion.
Conducting an Energy Audit
Energy audits can help identify areas where energy
investments can be made, thereby reducing energy used
in lighting, heating, cooling, or meeting other demands
of housing occupants. An inspection can evaluate the
worthiness or compliance with codes of energy-saving
measures, including accepted or written standards. For
example, if a new addition requires the equivalent of
R-19 insulation in the ceilings, this can be validated in
the inspection process. Whereas an audit is generally
informational, an inspection should validate that materials and workmanship have yielded a structure that
protects the occupants from the elements, such as rain,
snow, wind, cold, and heat. Potentially hazardous situations within a structure should be evaluated in an
inspection. The overall goal of a housing inspection in
the case of energy efficiency is to identify potential hazardous conditions and help to create conditions under
which the health and welfare of the occupants can be
enhanced, rather than put at risk.
The housing inspector should be aware that there is
variation (sometimes quite significant differences) in
heating degree days or cooling loads and in relative
humidity conditions within given regions. Local and
regional topography, as well as site conditions, can
affect temperatures and moisture.
Numerous Web sites listed in this chapter’s Additional
Sources of Information section discuss the procedures
for conducting energy audits. Local and regional utilities often offer audit services and assist with selecting
cost-effective conservation measures for given areas of
the United States.
References
1. Lawrence Berkeley National Laboratory. Energy star
insulation project: R-value guidelines. Berkeley, CA:
Lawrence Berkeley National Laboratory; 2004. Available
from URL: http://enduse.lbl.gov/Projects/Rvalue.html.
2. RoofHelp.com. R-value. Fort Worth, TX: RoofHelp;
1999. Available from URL: http://www.roofhelp.com/
Rvalue.htm.
3. State of Hawaii, Department of Business, Economic
Development, and Tourism, Energy Resources and
Technology Division. Ceiling insulation. Honolulu, HI:
State of Hawaii, Department of Business, Economic
Development, and Tourism; no date. Available from
URL: http://www.hawaii.gov/dbedt/ert/rf_insul.html.
13-11Chapter 13: Energy EfficiencyHealthy Housing Reference Manual
4. Oikos. Filling a floor with batt insulation. Energy Source
Builder 1995 [Apr]; 38. Available from URL: http://oikos.
com/esb/38/floorinsulation.html.
5. US Department of Energy. Energy savers: fact sheets.
Washington, DC: US Department of Energy; no date.
Available from URL: http://www.eere.energy.gov/
consumerinfo/factsheets.html.
6. US Department of Energy. Advances in glazing materials
for windows. Washington, DC: US Department of
Energy; 1994.
7. American Society of Heating, Refrigerating and
Air-Conditioning Engineers (ASHRAE). Standards; no
date. Atlanta: American Society of Heating, Refrigerating
and Air-Conditioning Engineers. Available from URL:
http://www.ashrae.org.
8. National Fenestration Rating Council. Search for energy
performance ratings. Silver Spring, MD: National
Fenestration Rating Council; no date. Available from
URL: http://www.nfrc.org/windowshop/surveybegin.aspx.
9. US Environmental Protection Agency. What is Energy
Star? Washington, DC: US Environmental Protection
Agency; no date. Available from URL: http://www.
energystar.gov/index.cfm?c=about.ab_index.
Additional Sources of Information
Alliance to Save Energy. Save energy at home. Available
from URL: http://www.ase.org/section/_audience/educators/edsavhome/.
Christian J, Kosnay J. Home Calculating whole wall
R-values on the Net. Energy Magazine Online,
November/December 1999.
Energy Information Administration. Available from URL:
http://www.eia.doe.gov.
Environmental Solar Systems. Available from URL:
http://www.environmentalsolarsystems.com/systems/.
Enviro$en$e: Common sense solutions to environmental
problems. Available from URL: http://es.epa.gov/.
Florida Power and Light. Building shell: insulation.
Available from URL: http://www.fpl.com/savings/energy_
advisor/PA_45.html.
Florida Power and Light. Online home energy survey.
Available from URL: http://www.fpl.com/home/ohes/
contents/online_home_energy_survey.shtml.
Hawaii Department of Business, Economic Development
and Tourism. Ceiling insulation. Available from URL:
http://www.state.hi.us/dbedt/ert/rf_insul.html.
National Association of State Energy Officials. Available
from URL: http://www.naseo.org.
Nexus Energyguide. Available from URL: http://www.
energyguide.com/default.asp.
Oak Ridge National Laboratory Buildings Technology
Center. Available from URL: http://www.ornl.gov/
ORNL/BTC.
Oak Ridge National Laboratory. Whole-wall thermal calculator performance. Available from URL: http://www.
ornl.gov/roofs+walls/whole_wall/wall-a30.html.
Oikos. Whole wall R-value ratings. Energy Source
Builder #47; October 1996. Available from URL: http://
oikos.com/esb/47/wholewall.html.
RoofHelp.com. R-value. Available from URL: http://
www.roofhelp.com/Rvalue.htm.
Senate Committee on Energy and Natural Resources.
Highlights of the Energy Policy Act of 2003 and the
Energy Tax Incentives Act of 2003. Available from URL:
http://energy.senate.gov/news/rep_release.cfm?id=203374.
Trandt J. Americans want energy efficiency.
Available from URL: http://healthandenergy.com/energy_
efficiency.htm.
US Department of Energy, Energy Efficiency and
Renewable Energy. Building envelope. Available from
URL: http://www.eere.energy.gov/ EE/buildings_envelope.html.
US Department of Energy, Energy Information
Administration. Available from URL: http://eia.doe.gov/.
US Environmental Protection Agency. Available from
URL: http://www.epa.gov.
US Environmental Protection Agency, Energy Star.
Available from URL: http://www.energystar.gov.
Wilson A. Thermal mass and R-value: making sense of a
confusing issue. EBN 1998 7(4). Available from URL:
http://www.buildinggreen.com/features/tm/thermal.cfm.
World Energy Efficiency Association. Available from
URL: http://www.weea.org/.
Healthy Housing Reference Manual13-12 Chapter 13: Energy Efficiency
14-1Chapter 14: Residential Swimming Pools and SpasHealthy Housing Reference Manual
Chapter 14: Residential Swimming Pools and Spas
“Most people assume if their young child falls into the pool,
there will be lots of splashing and screaming, and plenty of
time to react. In reality, a child slips into the water and often
goes under the surface. These drownings can happen quickly
and silently-without warning.”
Hal Stratton, Chair
U.S. Consumer Product Safety Commission,
2002– Present
Introduction
Swimming is one of the best forms of exercise available
and having a residential swimming pool also can provide
much pleasure. Nevertheless, it takes a great deal of work
and expense to make and keep the pool water clean and
free of floating debris. Without a doubt, a properly maintained and operated pool is quite rewarding. Home pools,
however, are sometimes referred to as attractive nuisances
or hazards. It is essential to be able to evaluate the risks
associated with a pool. A regulatory agent or consultant
must understand the total engineered pool system and be
capable of identifying all equipment, valves, and piping
systems. The piping system for a pool should be colorcoded to assist the pool operator or the owner to determine the correct way to operate the swimming pool. The
specific goal is to protect the owners, their families, and
others who may be attracted to a residential pool.
Residential pools and spas should provide clean, clear
water; water free of disease agents; and a safe recreational
environment. In addition, residential pools and spas
should have effective, properly operating equipment and
effective maintenance and operation.
Childproofing
Although it seems obvious, close supervision of young
children is vital for families with a residential pool. A
common scenario is a young child leaving the house
without the parent or caregiver realizing it. Children are
drawn to water, and they can drown even if they know
how to swim. All children should be supervised at all
times while in and around a pool.
The key to preventing pool tragedies is to provide layers
of protection. These layers include limiting pool access,
using pool alarms, closely supervising children, and being
prepared in case of an emergency. The U.S. Consumer
Product Safety Commission (CPSC) offers these tips to
prevent drowning:
• Fences and walls should be at least 4 feet high and
installed completely around the pool. The fence
should be no more than 2 inches above grade.
Openings in the fence should be a maximum of 4
inches. A fence should be difficult to climb over.
• Fence gates should be self-closing and self-latching.
The latch should be out of a small child’s reach. The
gate should open away from the pool; the latch
should face the pool.
• Any doors with direct pool access should have an
audible alarm that sounds for 30 seconds. The alarm
control must be a minimum of 54 inches high and
reset automatically.
• If the house forms one side of the barrier to the pool,
then doors leading from the house to the pool should
be protected with alarms that produce a sound when
a door is opened.
• Young children who have taken swimming lessons
should not be considered “drown proof”; young
children should always be watched carefully while
swimming.
• A power safety cover— a motor-powered barrier that
can be placed over the water area— can be used when
the pool is not in use.
• Rescue equipment and a telephone should be kept by
the pool; emergency numbers should be posted.
Knowing cardiopulmonary resuscitation (CPR) can
be a lifesaver.
• For aboveground pools, steps and ladders should be
secured and locked or removed when the pool is not
in use.
• Babysitters should be instructed about potential
hazards to young children in and around swimming
pools and their need for constant supervision.
• If a child is missing, the pool should always be
checked first. Seconds count in preventing death or
disability.
• Pool alarms can be used as an added precaution.
Underwater pool alarms can be used in conjunction
with power safety covers. CPSC advises consumers to
use remote alarm receivers so the alarm can be heard
inside the house or in other places away from the
pool area.
Healthy Housing Reference Manual14-2 Chapter 14: Residential Swimming Pools and Spas
• Toys and flotation devices should be used in pools
only under supervision; they should not be used in
place of supervision.
• Well-maintained rescue equipment (including a ring
buoy with an attached line and/or a shepherd’s crook
rescue pole should be kept by the pool.
• Emergency procedures should be clearly written and
posted in the pool area.
• All caregivers must know how to swim, know how to
get emergency help, and know CPR.
• Children should be taught to swim (swimming classes
are not recommended for children under the age of
4 years) and should always swim with a buddy.
• Alcohol should not be consumed during or just
before swimming or while supervising children.
• To prevent choking, chewing gum and eating
should be avoided while swimming, diving, or
playing in water.
• Water depth should be checked before entering a pool.
The American Red Cross recommends 9 feet as a
minimum depth for diving and jumping.
• Rules should be posted in easily seen areas. Rules
should state “no running,” “no pushing,” no drinking,”
and “never swim alone.” Be sure to enforce the rules.
• Tables, chairs, and other objects should be placed well
away from the pool fence to prevent children from
using them to climb into the pool area.
• When the pool is not in use, all toys should be
removed to prevent children from playing with or
reaching for them and unintentionally falling into
the water.
• A clear view of the pool from the house should be
ensured by removing vegetation and other obstacles
that block the view.
Hazards
Numerous issues need to be considered before building
residential pools: location of overhead power lines, installation and maintenance of ground fault circuit interruptors, electrical system grounding, electrical wiring sizing,
location of the pool, and type of vegetation near the pool.
The commonly used solar covers that rest on the surface
of the pool and amplify sunlight do an excellent job of
increasing the pool temperature, and they also increase
the risk for drowning. If children or pets fall in and sink
Figure 14.1. Pool Cover
below the cover, it can be nearly impenetrable if they
attempt to surface under it.
Winterizing the pool also can be hazardous. The pool
water in most belowground pools is seldom drained
because of groundwater pressure that can damage the
structure of the pool. Therefore, water in most home
pools is only lowered below the frost line for winter protection. In these cases, a pool cover is installed to keep
debris and leaves from filling the pool in the winter
months. The pool cover becomes an excellent mosquitobreeding area before the pool is reopened in the spring
because of the decomposing vegetation that is on the pool
cover, the rain that accumulates on the top of the pool
cover during the winter, and the eggs laid on the pool
cover in early fall and early spring. The cover also provides ideal conditions for mosquitoes to breed: stagnant
water, protection from wind that can sink floating eggs,
the near absence of predators, and warm water created by
the pool cover collecting heat just below the surface
(Figure 14.1).
Public Health Issues
Current epidemiologic evidence indicates that correctly
constructed and operated swimming pools are not a
major public health problem. They are preferable to bathing beaches because of the engineered controls designed
into pools. Poorly designed or operated pools, however,
can be major public health hazards. Data from CDC
between 1999 and 2000 show that 59 disease outbreaks
from 23 states were attributed to recreational water exposure and affected an estimated 2,093 people. Of the 59
recreational outbreaks, 44 (74.6%) were of known infectious etiology. Of the 36 outbreaks involving gastroenteritis, 17 (47.2%) were caused by parasites; 9 (25.0%) by
bacteria; 3 (8.3%) by viruses; 1 (2.8%) by a combination
of parasites and bacteria, and the remaining 6 (16.7%)
were of unknown cause. Of the 23 nongastroenteritisrelated recreational outbreaks, seven were attributed to
14-3Chapter 14: Residential Swimming Pools and SpasHealthy Housing Reference Manual
Pseudomonas aeruginosa, four to free-living amoebae,
one to Leptospira species, one to Legionella species, and
one to bromide. Sixteen of the 17 parasitic recreational
water outbreaks involving gastroenteritis; nine (24.3%)
were outbreaks of dermatitis; and six (16.2%) were
caused by Cryptosporidium parvum. The seventeenth
outbreak was caused by Giardia lamblia (intestinalis).
In 1999, an outbreak of Campylobacter jejuni was associated with a private pool that did not have continuous
chlorine disinfection and reportedly had ducks swimming in the pool [1].
Diseases
• Intestinal diseases: Escherichia coli O157:H7,
typhoid fever, paratyphoid fever, amoebic dysentery,
leptospirosis, cryptosporidiosis (highly chlorine
resistant), and bacillary dysentery can be a problem
where water is polluted by domestic or animal
sewage or waste. Swimming pools have also been
implicated in outbreaks of leptospirosis.
• Respiratory diseases: Colds, sinusitis, and septic
sore throat can spread more readily in swimming
areas as a result of close contact, or improperly
treated pool water, coupled with lowered resistance
because of exertion.
• Eye, ear, nose, throat, and skin infections: The
exposure of delicate mucous membranes, the
movement of harmful organisms into ear and nasal
passages, the excessive use of water-treatment
chemicals, and the presence of harmful agents in
water can contribute to eye, ear, nose, throat, and
skin infections. Close physical contact and the
presence of fomites (such as towels) also help to
spread athlete’s foot, impetigo, and dermatitis.
Injuries
Injuries and drowning deaths are by far the greatest problem
at swimming pools. Lack of bather supervision is a
prime cause, as is the improper construction, use, and
maintenance of equipment. Injuries include evisceration,
electrocution, entrapment, and entanglement. Some
particular problem areas include the following:
• loose or poorly located diving board,
• slippery decks or pool bottoms,
• poorly designed or located water slides,
• projecting or ungrated pipes and drains that can
catch hair or body parts,
• drain grates of inadequate size,
• improperly installed or maintained electrical
equipment, and
• improperly vented chlorinators and mishandled
chlorine materials.
Water Testing Equipment
It is essential that correct equipment be used and maintained for assessing the water quality of both swimming
pools and spas. The operators of pool and spas need to
monitor a wide range of chemicals that influence pool
operations and water quality. Their equipment should test
for chlorine, bromine, pH, alkalinity, hardness, and cyanuric acid build up. The chlorine should be measurable at
a range of 0 to 10 parts per million (ppm). Water pH levels should be accurately measured with an acid or base
test. A kit to check pool chemical levels usually includes
N,N-diethyl-p-phenylene-diamine (DPD) tablet tests for
free and total chlorine, and other one-step tablet tests for
pH, total alkalinity, calcium hardness, and cyanuric acids.
The homeowner should determine acid or base demand
using an already reacted pH sample in dropper bottles.
Paper test strips with multiple tests (including chlorine,
bromine, and pH) are also available, but the reliability of
these tests varies greatly. If used, they should be kept
fresh, protected from heat and moisture, and checked
against other test systems periodically if water quality
problems persist.
Swimming pools are engineered systems, with demanding
safety and sanitary requirements that result in rather
sophisticated design standards and water treatment systems. The size, shape, and operating system of the pool is
based on the following considerations:
• the intended use of the pool and the maximum
expected bather loading;
• the selection of skimmers, scuppers, or gutters,
depending on the purpose, size, and shape of the pool;
• the recirculation pump, whose horsepower and
impeller configuration are based on the distance,
volume, and height of the water to be pumped;
• the filters, which are sized on the volume of water to
be treated and the maximum gallons (liters) of water
per minute that can be delivered by the pump and the
type of filter media selected; and
• the chemical feeder sizes and types, which are based on
the chemicals used, total quantity of the water in the
system, expected use rates, and external environmental
factors, such as quantity of sunlight and wind that
affect the system.
Healthy Housing Reference Manual14-4 Chapter 14: Residential Swimming Pools and Spas
Disinfection
The length of time it takes to disinfect a pool depends,
for example, on the type of fecal accident and the chlorine levels chosen to disinfect the pool. If a fecal accident
is a formed stool, the faollowing chlorine levels will determine the times needed to inactivate Giardia:
Chlorine Levels (ppm) Disinfection Time
1.0 45 minutes
2.0 25 minutes
3.0 19 minutes
These times are based on a 99.9% inactivation of Giardia
cysts by chlorine, pH 7.5, and 77°F (25°C). The times
were derived from the EPA LT1ESWTR Disinfection
Profiling and Benchmarking Technical Guidance Manual
[2]. These times do not take into account “dead spots”
and other areas of poor pool water mixing.
If the fecal accident is diarrhea, the following chlorine
levels will determine the times needed to inactivate
Cryptosporidia:
Chlorine Levels (ppm) Disinfection Time
1.0 6.7 days
10.0 16 hours
20.0 8 hours
A CT value is the concentration (C) of free available
chlorine in parts per million (ppm) multiplied by the
time (T) in minutes (CT value = C×T ). The CT value
for Giardia is 45 and the value for Cryptosporidia is
9,600. If a different chlorine concentration or inactivation time is used, CT values must remain the same. For
example, to determine the length of time needed to disinfect a pool at 15 ppm after a diarrheal accident, the following formula is used: C×T = 9,600. Solve for time: T=
9,600÷15 ppm = 10.7 hours. It would, thus, take 10.7
hours to inactivate Cryptosporidia at 15 ppm. You can do
the same for Giardia by using the CT of 45.
CDC has Web sites that contain excellent information
about safe swimming recommendations, recreational
water diseases, and disinfection procedures for fecal accidents [3,4].
Content Turnover Rate
The number of times a pool’s contents can be filtered
though its filtration equipment in a 24-hour period is the
turnover rate of the pool. Because the filtered water is
diluted with the nonfiltered water of the pool, the turbidity continually decreases. Once the pool water has
reached equilibrium with the sources of contamination, a
6-hour turnover rate will result in 98% clarification if the
pool is properly designed. A typical-use pool should have
a pump and filtration system capable of pumping the
entire contents of the pool though the filters every 6
hours. To determine compliance with this 6-hour turnover standard, the following formula is used:
Turnover rate = pool volume (gallons)/flow rate×60
(minutes in hour)
Following is a sample calculation of the pool content
turnover rate using the rate of flow reading from the
flow meter:
Turnover rate = 90,000 (gallons in pool)/
180 gallons per minute×60 (minutes in hour)
8.3-hour turnover rate = 90,000 (pool volume in
gallons)/10,800
The above pool would not meet the required turnover
rate of 6 hours. The cause could be improperly sized
piping or restrictions in the piping, an undersized pump,
or undersized or clogged filters. This turnover rate would
probably result in cloudy water if the pool is used at the
normal bather load. The decreased circulation would also
make it difficult for the disinfecting equipment to meet
the required levels.
Filters
Pool filters are not designed to remove bacteria, but to
make the water in the pool clear. Normal tap water looks
quite dingy if used to fill a pool and, in some cases, the
bottom of the pool is not visible. The maximum turbidity
level of a pool should be less than 0.5 nephelometric turbidity units. Pool filters should be sized to ensure that the
complete contents of the pool pass through the filter once
every 6 hours. Home pools typically use one of three
types of filters.
High-rate Sand Filters
High-rate sand filters were introduced more than 30 years
ago and reduced the size of the conventional sand filter
by 80%. The sand filter is the most popular filter on the
market. High-rate sand filters use a silica sand that has
been strained to give it a uniform size. It is referred to as
pool-grade sand #20 silica. The sand is normally 0.45
millimeters (mm) to 0.55 mm in diameter. As water
passes through the filter, the sharp edges of the sand trap
the dirt from the pool water. When the backpressure of
the filter increases to 3 to 5 psi, the filter needs to be
14-5Chapter 14: Residential Swimming Pools and SpasHealthy Housing Reference Manual
cleaned. This is usually accomplished by reversing the
flow of the water through the filter and flushing the dirt
out the waste pipe until the water being discharged
appears clear. These filters perform best when used at
pressure levels below 15 to 20 gallons per minute,
depending on the manufacturer of the filter.
Cartridge Filters
Cartridge filters have been around for many years, but
only recently have gained in popularity in the pool industry. They are similar to the filter on a car engine. The
water is passed through the cartridge and returned to the
pool. When the pressure of a cartridge filter increases
approximately 5 psi, the pump is turned off; and the top
of the filter is removed. The cartridge is removed and
either discarded and replaced or, in some cases, washed.
Diatomaceous Earth
Diatomaceous earth (DE) is a porous powder made from
the skeletons of billions of microscopic animals that were
buried millions of years ago. There are two primary types
of DE filters, but they both work the same way. Water
comes into the filter, passes through the DE, and is
returned to the pool. If properly sized and operated, DE
filters are considered by some to provide the highest quality of water. They are capable of filtering the smallest particle size of all the filter types. It is usually adequate to
change the DE once every 30 days. However, if your pool
water is very dirty, it is not uncommon to change it 3–4
times a day until the water is clear. The frequency of
backwashing will depend on many factors, including the
size of your filter, flow rate of your plumbing, and the
bather load in your pool. When the pressure reading on
the filter reaches the level set by the manufacturer’s manual, it will be ready for backwashing.
Filter Loading Rates
The specification plate on the side of approved residential
or commercial swimming pool filters contains such
information as the manufacturer, type of filter, serial
number, surface area, and designed loading rate. Knowing
the surface area of the filter permits calculation of the
number of gallons flowing through the filter per minute.
An excessive flow rate can push the media into the pool
or force pool solids and materials thought the media,
resulting in turbid water. Figure 14.2 shows a typical
home pool treatment system. Regulations typically specify
how much water can be filtered through the various types
of pool filtration systems.
Figure 14.2. Typical Home Pool Equipment System
Disinfectants
Many disinfectants are used in pools and spas around the
world, including halogen-based compounds (chlorine,
bromine, iodine), ozone, and ultraviolet light with hydrogen peroxide. Those used most often are chlorine, bromine, and iodine, and each has advantages and
limitations.
Chlorine— Pools can be disinfected with chlorine-releasing compounds, including hypochlorite salt compounds.
Calcium hypochlorite is inexpensive and popular for
cold-water pools, but not suitable for hot pools and spas
because it will promote scaling on heat exchangers and
piping. Chlorine levels can be rapidly reduced with high
use and regular checks should be made to ensure maintenance of disinfection. Some adjustment of pH is required
for most forms of chlorine disinfection. When chlorine
gas is used, a fairly high alkalinity needs to be maintained
to remove the acid formed during dosing [5]. Sodium
hypochlorite is a liquid chlorine, and has a pH of 13,
causing a slight increase in the pH of the pool water,
which should be adjusted with an acidic mixture. The
sun’s rays will degrade sodium hypochlorite. Chlorinated
isocyanate is available in three forms-granular, tablet, and
stick. The granular form contains 55%– 62% available
chlorine and the stick and tablet form contain 89% available chlorine [6].
Healthy Housing Reference Manual14-6 Chapter 14: Residential Swimming Pools and Spas
Bromine— Bromine needs to be used at levels twice
those of chlorine to achieve similar disinfection. Bromine
is available as the sodium or potassium salts. In the presence of ammonia, bromine rapidly forms relatively unstable ammonia bromamines that possess disinfection
efficiencies comparable to that of free bromine. It is also
unnecessary to destroy ammonia bromamines because
they do not produce irritating odors [5].
Iodine— Potassium iodide is a white, crystal chemical.
This chemical needs an oxidizer, such as hypochlorite, to
react with organic debris and bacteria. Iodine does not
react with ammonia, hair, or bathing suits, or cause eye
irritation, but it can react with metals, producing greenish-colored pool water [6].
Ozone— Ozone is a very powerful oxidant and is effective against viruses. It can only be generated at the point
of use and commercial generation units are safe for use.
Ozone dosing is only practical where there is water circulating off-pool because adequate ozone-water mixing is
essential for maximum oxidation. Ozone generators may
be of the ultraviolet lamp or corona discharge type. The
ultraviolet lamp efficiency reduces with time and the
lamp and associated activated charcoal filter will need
replacement [5].
Ultraviolet Light— Ultraviolet light, like ozone, is sometimes used for off-pool water disinfection. Ultraviolet
light has no effect on pH or color and has little effect on
the chemical composition of the water. However, color,
turbidity, and chemical composition of the water can
interfere with ultraviolet light transmission. The water
must be adequately treated before ultraviolet light exposure. Hydrogen peroxide is often used for this purpose as
it is relatively safe in low concentrations, is nonflammable, and produces oxygen and water as end products. For
the ultraviolet light plus hydrogen peroxide system to be
effective, it must operate 24 hours a day. Ultraviolet light
disinfection is not pH dependent, but the addition of
hydrogen peroxide results in slightly acidic conditions [5].
Silver-copper Ionization— Sanitizing can be accomplished by using an ionizing unit that introduces silver
and copper ions into the water by electrolysis, or by passing an electric current through a silver and copper electrode. The limiting factors in using this system in the
pool and spa are cost, slow bactericidal action, and potentially high contaminant levels caused by bather loads.
Also, black spots can form on pool surfaces if the proper
parameters of water chemistry are not maintained. An
approved chemical disinfectant must be used with an ionizing unit [6].
The effective use of halogen disinfectants is based on the
pH, hardness, and alkalinity of the water. Improper pH,
hardness, and alkalinity levels in the pool can render high
levels of disinfectant useless in killing disease-causing
organisms. Table 14.1 summarizes water-quality problems
that affect pools and suggests corrective actions.
Effect of pH
The ideal pH to avoid eye irritation is 7.3. Bacteria- or
algae-killing effectiveness is improved with an even lower
pH. National standards typically recommend a range of
7.2 to 7.6, which is cost-effective. Table 14.2 demonstrates
the loss of disinfection as pH increases.
Chlorine Disinfectants
The options for selecting the form of chlorine disinfectant
to use in pools are quite varied, and the choices are complex. Table 14.3 gives the properties of each form. Gas
chlorine costs the least, and the relative cost of each form
of chlorine increases as you move right across the table.
The cost of the disinfectant tends to be less the higher the
concentration of available chlorine. The safety issues are
more complex than they might appear. The hazards of gas
chlorine are well known. The solid forms of chlorine, such
as calcium hypochlorite, are quite reactive. When exposed
to organic compounds, they can generate a great deal of
heat and are potentially explosive. Because solid chlorine
seems inert to the untrained worker, it is often stored
beside motor oil or gasoline or left in where moisture can
start a chemical reaction. Even a pencil with a graphite
core that drops from a shirt pocket into a container of calcium hypochlorite could result in a chemical reaction
leading to a fire that would release free chlorine gas [7].
The following chemical reactions produce chlorine byproducts that reduce the effectiveness of chlorine and
cause most eye irritation.
Cl2 + H2O = HCl + HOCl
Chlorine + Water = Hydrochloric Acid +
Hypochlorous Acid
HOCl + NH3 = H2O + NH2Cl
Hypochlorous Acid + Ammonia =
Water + Monochloramine
HOCl + NH2Cl = H2O + NHCl2
Hypochlorous Acid + Monochloramine =
Water + Dichloramine
HOCl + NHCl2 = H2O + NCl3
Hypochlorous Acid + Dichloramine =
Water + Nitrogen Trichloride
14-7Chapter 14: Residential Swimming Pools and SpasHealthy Housing Reference Manual
Water Quality Issue (Symptoms) Potential Problems (Root Causes) Corrective Approaches (Actions)
Air bubbles coming from inlets 1. Air in filter shell (easy fix) 1. Bleed air off of top of filter shell.
2. Leak in hair and lint strainer, pipe,
valves, or fittings on suction side of
pump (may be difficult to fix)
2. Check seal around opening of hair
and lint strainer. Locate leaking fitting
and seal.
Foam on water, around floating
objects, and on sides of pool
1. Low hardness of water (easy fix) 1. Maintain minimum of 200 ppm calcium
hardness, but less than 400 ppm.
2. Effect of algaecides (do not need) 2. Do not use algaecides, but maintain 1
ppm of free chlorine at minimum and a
pH of 7.2–7.3. (pH of 7.2 is preferable)
for algae-free water.
3. Spillage of detergent into pool 3. Backwash filters for extended time and
add makeup water. If foam is still a
problem, add defoaming agent.
Cloudy water 1. Inadequate turnover rate 1. Check pump capacity and flow rate.
2. Filter media corrupted, channeled, or
creviced.
2. If sand, clean filter and replace media,
if necessary. If diatomaceous earth (DE)
filter, wash filter bags in weak acid
solution.
3. Excessive filter pressure. 3. Backwash filter, bleed air pressure from
filter shell, check pump for proper
sizing.
4. High pH or alkalinity above 150 ppm. 4. Reduce pH to maximum of 7.6 and
alkalinity to less than 150 ppm.
Milky water (uniform water color
with white, opaque appearance)
DE entering pool from DE filter leakage Check filter bags for tears or holes and the
mounting of the bags on the filter septa.
Expect 24-hour minimum filtering to clear
water.
Dull green color, varying density Algae growth Super-chlorinate, then maintain pH at 7.6
(preferably 7.2) and disinfectant level of
1 ppm or higher.
Bright green color Dissolved iron Adjust pH to between 7.2 and 7.6, adjust
disinfectant level to between 1 and 1.5
ppm. Iron should precipitate to ferrous
state (brown); backwash repeatedly to
remove. Expect 24 to 46 hours of filtering
to clear water.
Bluish green color Copper damage from low pH Raise pH to 7.6, increase hardness to
200 ppm and alkalinity to at least 150
ppm. Perform a saturation index calculation. Adjust water to slightly above +0.5
to achieve scale-forming water to isolate
before equipment damage.
Reddish brown water, uniform in
color and texture
Precipitated iron (ferrous) Adjust pH and disinfectant level and backwash filter as needed until clear.
Table 14.1. Pool Water Quality Problem Solving [7]
Tables 14.1–14.4 serve as a quick problem-solving reference for the home pool owner and operator.
The CDC Web site (www.cdc.gov/healthyswimming) provides a great deal of useful information for
both the inspector and the homeowner.
Healthy Housing Reference Manual14-8 Chapter 14: Residential Swimming Pools and Spas
Pool Water Hardness and Alkalinity
The ideal range of water hardness for a plaster pool is 200
to 275 ppm. The ideal range for a vinyl, painted, or fiberglass surface is 175 to 225 ppm. Excess hardness causes
scaling, discoloration, and filter inefficiency. Less than
recommended hardness results in corrosion of most contact surfaces.
Alkalinity should be 80 to 120 ppm. High alkaline levels
cause scale and high chlorine demand. Low levels cause
unstable pH. Sodium bicarbonate will raise the alkalinity
level. The pool water will be cloudy if alkalinity is over
200 ppm.
Liquid Chemical Feeders
Positive Displacement Pump
A positive displacement pump is preferable to erosion disinfectant feeders. Positive displacement pumps can be set
to administer varied and specific chemical dosage rates to
ensure that a pool does not become contaminated with
harmful microorganisms. A positive displacement pump
does need routine cleaning, descaling, and servicing.
Running a weak muratic acid or vinegar solution through
the pump weekly can minimize most major servicing of the
pump. Most service on the pump involves one of four areas:
HoCl H + OCl Hypochlorous Acid—
More Increases Effectiveness
[Percent of Chlorine as HOCl] Hydrogen Ion [pH]
Hypochlorite Ion—
More Reduces Effectiveness
[Percent of Chlorine as OCl]
90 6.5 10
73 7.0 27
66 7.2— IDEAL 34
45 7.6— IDEAL 55
21 8.0 79
10 8.5 90
Table 14.2. pH Effect on Chlorine Disinfection [7]
Gas Chlorine Sodium Hypochlorite Calcium Hypochlorite Dichloro Trichloro
Percent Chlorine 100 10–15 65–70 56–62 90
Effect on pH Lowers pH Raises pH Raises pH Neutral Lowers pH
Sunlight Effects Considerable Yes Yes Little loss Little loss
Physical Form Gas Liquid Granular or tablets Granular only Granular or tablets
Table 14.3. Chlorine Use in Swimming Pools
1. the check valves are scaled, their springs are weak,
or valves are no longer flexible;
2. the diaphragm is cracked, leaking, or not flexible;
3. the drive cam needs replacement or requires
adjustment; or
4. the motor requires replacement.
Erosion and Flow-through Disinfectant Feeders
These feeders work by the action of water moving around
a solid cake of chlorine and eroding the cake. The feeders
work quite well for smaller pools, but require considerable care and maintenance. The variables that affect the
effectiveness of erosion feeders are
1. solubility of the chlorine cake or tablet;
2. surface area of the cake or tablet;
3. amount of water flowing around the cake or tablet;
4. concentration of chlorine in the cake or tablet; and
5. number of cakes or tablets in the feeder.
Note: For safety reasons, the disinfectant cake must not
be accessible.
14-9Chapter 14: Residential Swimming Pools and SpasHealthy Housing Reference Manual
Minimum Ideal Maximum Comments
Water Clarity
Crystal-clear water at
all times is the goal
Main drain
visible
Crystal clear,
object the size
of a dime easily seen from
pool deck at
main drain,
water sparkles
None Lack of clarity is often due to malfunctioning
or undersized filters. Other problems may be
improperly sized pump, air collecting in the
filter shell, or operator not running filter 24
hours per day.
Disinfectant Levels
Free chlorine
Standard pool
Wading or shallow
pool for children
4
3
4
3
4
3
Continuous levels at 1 to 1.5 ppm minimum.
Super-chlorinate indicators: high chlorine
level, eye irritation, or algae growth.
Super-chlorinate indicators: High chlorine
levels, eye irritation or algae growth.
Continuous levels.
Combined chlorine None None 0.5
Bromine
Wading or shallow
pool for children
2
4
5
7
10
10
Iodine ppm Consult product
manufacturer
— — —
Chemical Values
Hardness, CaCO3 150 200 –400 500+ If difficult to control, use a different
disinfectant.
Heavy metals None None None Check algaecide for heavy metal presence or
by-products of corrosion (partial water
replacement may be recommended).
Stabilizer,
cyanuric acid
10 30–50 100 If level exceeds 100 ppm, partial water
replacement recommended.
Algae, bacteria None None None Shock treat and maintain required levels of
disinfectant and 7.2 to 7.6 pH.
Table 14.4. Swimming Pool Operating Parameters [7]
Spas and Hot Tubs
Hot tubs (large tubs filled with hot water for one or more
people) or spas (a tub with aerating or swirling water) are
used for pleasure and are increasingly being recommended for therapy. The complexity of these devices
increases with each new model manufactured. Newer
models often have both ozone and ultraviolet light emitters for enhanced disinfection (see Disinfectants section
earlier in this chapter). However, the environment of the
spa and hot tub, if not cleaned and operated correctly,
can become a culture medium for microorganisms.
Because the warm water is at the ideal temperature for
growth of microorganisms, good disinfection is critical.
Table 14.5 provides suggested hot tub and spa operating
parameters. It is essential that all equipment works properly and that the units are cleaned and disinfected on a
routine basis. Monitoring the water temperature is very
important and, depending on the health of the user, can
be a matter of life and death. Time in the heated water
should be limited, and the temperature for pregnant users
should be below 103°F (39°C) to protect the unborn
baby.
Healthy Housing Reference Manual14-10 Chapter 14: Residential Swimming Pools and Spas
Minimum (ppm) Ideal (ppm) Maximum (ppm) Comments
Disinfectant Levels
Free chlorine 3 4 10 Continuous levels. Super-chlorinate when combined level exceeds 0.2.
Combined
chlorine None None 0.5
Super-chlorinate indicators: High chlorine
levels, eye irritation or algae growth.
Bromine 4 5 10 Continuous levels.
Iodine ppm Consult product manufacturer
Ozone, ultraviolet
light, hydrogen
peroxide, and
others
Consult product
manufacturer
Use also requires a disinfectant in most
health jurisdictions.
Chemical Values
pH 7.2 7.3 7.6 Ideal range: 7.2–7.6.
Total alkalinity,
CaCO3
60 80–100 180
Dissolved solids 300 NA 2,000
Excess solids many lead to hazy water and
corrosion of fixtures (may need partial
water replacement).
Hardness, CaCO3 150 200–400 500+
If difficult to control, use a different
disinfectant.
Heavy metals None None None
Check algaecide for heavy metal presence or
by-products of corrosion (partial water
replacement may be required).
Stabilizer,
cyanuric acid 10 30–50 100
If level exceeds 100 ppm, partial water
replacement may be required.
Algae, bacteria None None None
If observed, shock treat and maintain
required levels of disinfectant and the
appropriate pH.
Table 14.5. Spa and Hot Tub Operating Parameters [7]
References
1. Lee HL, Levy DA, Craun GF, Beach MJ, Calderon RL.
Surveillance for waterborne-disease outbreaks— United
States, 1999–2000. MMWR 2002; 51(SS08):1–28.
Available from URL: http://www.cdc.gov/mmwr/preview/
mmwrhtml/ss5108a1.htm.
2. US Environmental Protection Agency. LT1ESWTR
Disinfection profiling and benchmarking: technical
guidance manual. Washington, DC: US Environmental
Protection Agency; 2003. Available from URL: http://
www.epa.gov/safewater/mdbp/pdf/profile/lt1profiling.pdf.
3. Centers for Disease Control and Prevention. Healthy
swimming. Atlanta: US Department of Health and
Human Services; no date. Available from URL:
http://www.cdc.gov/healthyswimming/.
4. Centers for Disease Control and Prevention. Fecal
accidents response recommendations for aquatics staff.
Atlanta: US Department of Health and Human Services;
no date. Available from URL: http://www.cdc.gov/
healthyswimming/fecalacc.htm.
14-11Chapter 14: Residential Swimming Pools and SpasHealthy Housing Reference Manual
5. Broadbent C. Guidance on water quality for heated spas.
Rundle Mall, South Australia, Australia: Public
Environmental Health Service; 1996. Available from
URL: http://www.dh.sa.gov.au/pehs/publications/
monograph-heated-spas.pdf.
6. Michigan State University Pesticide Education Program.
Swimming pool pest management: category 5A, a training
guide for commercial pesticide applicators and swimming
pool operators. Chapter 3: pool disinfectants and pH. East
Lansing, MI: Michigan State University; no date. Available
from URL: http://www.pested.msu.edu/BullSlideNews/
bulletins/pdf/2621/E2621chap3.pdf.
7. National Swimming Pool Foundation. Certified pool-spa
operator handbook, 2004. Colorado Springs, CO:
National Swimming Pool Foundation; 2004. Available
from URL: http://nspf.org.
Additional Sources of Information
American Academy of Pediatrics. Available from URL:
www.aap.org.
American National Standards Institute. Available from
URL: http://www.ansi.org.
American Red Cross. Available from URL:
www.redcross.org.
American Trauma Society. Available from URL:
www.amtrauma.org.
Association of Pool and Spa Professionals. Available from
URL: http://www.nspi.org/.
Centers for Disease Control and Prevention, National
Center for Injury Prevention and Control. Available from
URL: www.cdc.gov/ncipc/factsheets/drown.htm.
For more information about the CDC fecal accident
recommendations, go to URL: http://www.cdc.gov/
healthyswimming/fecal_response.htm.
For additional information about cryptosporidiosis,
go to URL: http://www.cdc.gov/healthyswimming/
cryptofacts.htm.
See also Web-based Injury Statistics Query and
Reporting System (WISQARS) [Online]. (2002).
National Center for Injury Prevention and Control,
Centers for Disease Control and Prevention. Available
from URL: www.cdc.gov/ncipc/wisqars.
Children’s Safety Network. Available from URL:
http://www.childrenssafetynetwork.org.
Chlorine Institute, Inc. Available from URL:
http://www.cl2.com.
National Safe Kids Campaign. Available from URL:
http://www.safekids.org.
National Safety Council. Available from URL:
http://www.nsc.org/.
National Swimming Pool Foundation. Available from
URL: http://www.nspf.com/.
Think First National Injury Foundation. Available from
URL: http://www.thinkfirst.org.
US Consumer Product Safety Commission. Available
from URL: http://www.cpsc.gov.

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