Indoor Air Quality: Build Tight, Ventilate Right

Dust, allergens, volatile organic compounds (VOCs), mold, and hazardous cleaners found in a typical home (yes, even a new home) can create indoor air pollution worse than that of a major industrial city. These pollution levels can be five times higher than those found in outdoor air. Considering that we spend up to 90% of our time indoors, it is no wonder the Environmental Protection Agency (EPA) considers indoor pollution to be one of the top-five public health concerns, and it can potentially cause asthma, allergies, immune system problems, and even cancer.

Sources of Indoor Air Pollutants

Combustion. One of the most obvious and serious Indoor Air Quality (IAQ) problems comes from the backdrafting of water heaters and furnaces. (Backdrafting is when negative pressure inside a home, usually created by exhaust or vent fans, pulls noxious gases into the living area.) Combustion of oil, gas, and wood create, among other things, carbon monoxide, particulates, and nitrogen dioxide.

Carpeting. Carpeting has been the scapegoat for many IAQ problems. While carpeting can be a source of VOCs, the pro-carpet Carpet & Rug Institute (CRI) insists that most VOCs dissipate from new carpet within 48 to 72 hours of installation. Dust mites, however, are a real concern for allergy sufferers, and carpeting can harbor them if it is not kept dry and clean. (In general, dust mites prefer moist, warm environments like bedding and pillows instead of carpeting.)

Asbestos and vermiculite. Asbestos fibers can be found in some insulation and roofing of older homes. Left undisturbed, these small fibers do not pose a problem, but if they become airborne during remodeling, insulation work, or demolition, they can nestle into the lungs and cause real damage. Vermiculite is a less well-known danger. Vermiculite is used as a pour-in attic insulation, but too can contain asbestos, because asbestos and vermiculite are often found in the same geological area and accidentally mined together. An EPA study found 15% of vermiculate contains asbestos, but removing asbestos (or contaminated vermiculite) from a home can be an expensive job, requiring a licensed asbestos remover.

Mold. Mold becomes a problem when it finds a moist spot (and a food source) in the home and the spores become trapped and concentrated indoors. Leaking roofs, poorly insulated pipes, poor ventilation, damp basements, and poorly designed wall systems that trap moisture can all cause mold problems, which is especially troublesome for people with asthma and allergies. Ensure that moisture is kept out of the building shell and interior humidity stays below 50%. Air barriers are the latest tool in moisture control. Icynene^® acts as both an insulation and air barrier material to minimize the potential for moisture-related problems like mold growth.

Other biological pollutants. Pollen, pet dander, mildew, and dropping from cockroaches, dust mites, and mice can all generate strong allergens.

Paint, finishes, adhesives, strippers, and household cleaners. The use of some paint strippers can increase a home's VOC levels to over 1,000 times the EPA's limits. The best way to deal with this problem is to avoid using toxic products in the first place.

Sealing the Building Envelope

Looking at a house as a complete system (a thermal envelope) is the first step toward achieving good IAQ. “Build tight, ventilate right” is a good motto for sustainable buildings.

Ventilation

Once the home is “built tight” it is time to “ventilate right.” That starts with a strategy for replenishment air and ventilation, which is often left out of residential HVAC systems. Yet ventilation (the V in HVAC) is critical for healthy indoor air quality and for reducing humidity and interior moisture problems.