Green building is resource efficient, contributes to a healthy environment, and provides a healthy home for occupants. According to the EPA, most Americans spend up to 90% of their time indoors. Home design includes many amenities people feel they need to make them happy and comfortable in their home. A home should also ensure that sources of indoor pollutants are limited, and those that exist will be diluted or removed from the space.

Because of the amount of time people spend inside, indoor air quality is important. Indoor air problems are usually caused by gases or particles. Many building materials and building designs contribute to indoor air problems. Outside sources can also become indoor pollutants if carried in on shoes or located next to fresh air returns for the house. Ventilation provides fresh air to dilute concentrations of pollutants and to carry them outside. Inadequate ventilation can add problems by allowing moisture and temperature levels to rise.

Reasons to Change

Some people, especially children, elderly, and those with allergies are particularly sensitive to indoor pollutants. Adverse health effects may include respiratory, neurological, and skin conditions, impairment of brain function (mental retardation in children), lung disease and cancer. To reduce these effects, apply a "systems approach" where the interaction of all elements of the building site, building envelope, mechanical systems, and occupants are considered.

Primary Indoor Air Pollutants
Pollutant	Source
Formaldehyde	Primary source in homes is particle-board, hardwood plywood paneling, and medium density fiberboard. Also various sources including smoking, household products, and the use of unvented, fuel-burning appliances, glues and adhesives, and preservative in some paints and coating products.
Radon	Radioactive breakdown of soil and rock, occurs virtually everywhere
Combustion Pollutants	These include carbon monoxide, carbon dioxide, sulfur dioxide, nitrogen dioxide. Unvented kerosene and gas space heaters, woodstoves, fireplaces, gas stoves, water heaters and appliances; improperly installed or maintained chimneys and flues, and cracked furnace heat exchangers; "back-drafting" of fireplaces, woodstoves and gas appliances with no dedicated outdoor air supply.
Secondhand Smoke	Smoke coming from burning end of cigarette, pipe or cigar or exhaled by smoker
Particulates	Fireplaces, woodstoves, kerosene heaters and secondhand smoke.
Volatile Organic Compounds (VOCs)	Fuels, paints, varnishes, adhesives and wax. Household cleaning, disinfecting, cosmetic, degreasing, and hobby products containing organic solvents;
Biologicals (allergens)	(Including: dust mites, mold, pet dander, pollen, etc.) Various plant, animal, human and mechanical sources, typically enhanced through moisture and relative humidity over 30 - 50%.
Asbestos	Mineral fiber used for insulation and as a fire-retardant in pipe and furnace insulation materials, asbestos shingles, millboard, textured paints and other coating materials, and floor tiles.
Asbestos Lead	Old lead-based paint improperly removed from surfaces by dry scraping, sanding, or open-flame burning.
Pesticides	Insecticides and disinfectants used in the home, carried in from contaminated soil, or stored.
Sources: www.montana.edu/wwwcxair/ and www.epa.gov/iaq/pubs/insidest.html#IAQHome

Builders can reduce the risks of poor indoor air quality. Reduced liability and increased community relations will result from homes built with indoor air quality considerations. Homeowners and the community at large will benefit from reduced health impacts caused by poor indoor air quality in homes. Money spent on insurance, medication, remediation activities, and lost productivity is money often taken from expenditures that keep local economies strong.

P2 in Action: Eliminate Sources

It is cheaper and easier to avoid pollutants than to cover or clean them up. For unavoidable pollutants, and those created by the homeowner, plan for fresh air exchange through mechanical ventilation and air cleaning devices.

Eliminate toxic materials and pollutant breeding grounds as often as possible.

• Select easy to clean floorings and those that don't "offgas" (e.g. ceramic tile, linoleum, wood, short fiber carpet or area rugs) to avoid pollutant buildup.
• Vent bathrooms and other fans and the dryer outdoors, not in attic or other interior space.
• Provide sufficient water management around the foundation, attic and walls (waterproof system, drain tile or vapor retarder) to reduce moisture, mold and humidity.
• Select only no or low VOC paints, and for flooring, non-toxic adhesives or mechanical fasteners.
• Avoid cabinets and furnishings made from particleboard that may contain formaldehyde in the glue or seal particleboard components with no or low VOC sealant.

Separate potential pollutants from the living space.

• Build an airtight structure to keep insulating materials sealed away from occupants.
• Select sealed combustion or power vented heating appliances (own air supply and vent to exterior).
• Encapsulate or permanently cover potential pollutants such as asbestos or lead paint.

P2 in Action: Ventilate

Provide adequate mechanical ventilation within the home to ensure enough fresh air intake for dilution of pollutants, removal of pollutants and efficient operation of appliances. Organizations working in the fields of building energy, green buildings, heating, refrigeration, and ventilation provide criteria for mechanical ventilation system rates and parameters, i.e. American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) http://www-epb.lbl.gov/publications/lbnl-42975.pdf. Guidelines often include requirements for testing of the system.

If installing or using products that may contribute to unhealthy indoor air, take extra precautions to reduce exposure to the interior of the home, e.g. lay carpets and draperies out to vent or offgas in a clean, dry area outside of the home for at least 24 hours before installation.

P2 in Action: Be Proactive

Consider installing monitoring and remediation systems during new construction, when they can save lives, prevent illness, and add very little additional cost. For example:

• Install a carbon monoxide detector near combustion appliances.
• Radon resistant construction reduces moisture levels and associated problems and only costs $100 - $300 while increasing the value of the home. Nearly one in15 homes in the U.S. is estimated to have elevated radon levels. It is much easier and less expensive to provide this type of system during new construction activities.

"The key to designing and building a healthy house is to choose the construction materials that are most benign, and put them together in a manner that enhances your health rather than compromises it." John Bower, author of Healthy House Building: A Design and Construction Guide, and internationally recognized healthy housing expert