The EPA estimates that as many as 15% of Americans are allergic to their own homes. According to the New England Journal of Medicine, 40% of children born today will suffer some form of respiratory disease.


Green Building Best Practices

  • Use the full range of green-building strategies to eliminate sources of moisture inside the building envelope that contribute to the growth of mold.
  • Make sure the house is adequately ventilated and that air is filtered where possible to remove contaminants such as animal dander and pollen.
  • Learn to recognize the source of chemical contaminants and isolate or eliminate those products from inside the building envelope.
  • Look for safer alternatives to products that leach or off-gas hazardous materials.
  • Install carbon monoxide detectors.
  • Seal the wall between an attached garage and the rest of the house.
  • Install a radon collection system beneath the concrete slab or basement floor and rough in a means of exhausting the air as the house is framed.
  • When air quality problems are suspected, hire an expert to test the home.

Contaminants and Their Impact on Health

Maintaining high indoor air quality, an important component of green building, becomes more complex as the number of chemicals used in household furnishings, products, and building materials continues to expand. Additionally, as houses become tighter, they are more likely to trap chemicals in the air we breathe.

 See Chapter 14 on  Indoor Air Quality Green from the Ground Up book for more details.

Contaminants in our homes fall into two broad categories:

  • Biological - originate indoors or outdoors and are known as bioaerosols and includes mold, dust mites, pollen, animal dander and bacteria.
  • Chemical - includes both gases and particulates

Biological Contaminants


Mold grows on organic material, especially cellulose. The most common location for mold to grow is in the wall cavities of wet areas. Mold can come from outside sources, leaks in siding and housewrap or inside sources, like leaks in plumbing inside the walls. By the time you see evidence of mold, it has already grown into the wood or paper that supports it.

Where to Look for Mold

Mold and mildew may be found in the ductwork of your heating or cooling system. Sometimes they are found in the coils of an air conditioner,  in the connection between the air conditioner and the ductwork or on a dirty furnace and air-conditioning filters. Plumbing leaks and dampness in attics, basements, and crawlspaces can increase humidity inside your home and promote the growth of agents.

How to Prevent Mold

Mold can cause unsightly stains and may release varying levels of toxic chemicals called mycotoxins into the air. Keep moisture out of wall and ceiling cavities. Spray mold prevention coatings on the studs before the trades arrive.

Dust Mites

Dust mites and their waste are the most common allergens in indoor air. They live in rugs, carpets, sheets, mattresses, pillows and upholstered furniture. They can't be eliminated but reducing the amount of floor area covered by carpeting can help.

Chemical Contaminants

Every year, 700 new chemicals are introduced into the environment but less than 1% of them are tested for their impact on human health. Many of these end up in our homes in "new and improved" products.


Formaldehyde is a potent eye, upper respiratory and skin irritant. It off-gases for years leading to a number of potential health problems and is known to cause cancer in animals and is a suspected human carcinogen.  It is also one the most widely used adhesives in the construction industry. It is very common in wood products made with particleboard, such as cabinets, countertops and shelving.

Vinyl Chloride

You may not have seen vinyl chloride but you have smelled it - the smell of a new car, beach balls, and shower curtains. Vinyl chloride is not toxic when it is bonded into chains, such as PVC, but it is present as PVC is manufactured and often in its disposal, particularly when burned.


Petroleum-based chemicals added to plastics help make the material more useful, make our upholstery comfier and our pipes more flexible. Today, phthalates are one of the top offenders in a group of 70 suspected endocrine-disrupting chemicals (EDCs) that we use in our homes and yards. 

Styrene-butadiene latex

Most of the carpeting sold for residential use includes a solvent-based adhesive and a binder that helps hold carpet fibers to the backing. The "new carpet odor" is usually 4-phenylcyclohexene (4-PCH), which is a by-product of the styrene-butadiene latex binder.  A Johns Hopkins University School  of Hygiene and Public Health study supported the hypothesis that exposure to butadiene is associated with a risk of leukemia.


Radon is the second most frequent cause of lung cancer behind smoking in the U.S.. It is a radioactive gas that percolates through rock and soil to find its way into the house.