DIY Network

Air Flow From "Healthy Household Workshop" episode DHHW-103

The Environmental Protection Agency calls poor indoor air quality one of the most urgent health risks today -- yet Americans spend 90 percent of the time indoors. Because modern homes are well-insulated and trap dust, pollen, smoke and other contaminants, adequate ventilation and filtration is essential to protecting your health.

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Not only do we spend more time indoors than ever before - our allergy and asthma rates are soaring.

Asthma and Air Flow

Indoor air pollutants are asthma triggers. Asthma is rapidly rising -- with 15 millions affected and 14 million school days lost to asthma each year. Steve Klossner, of the American Lung Association, says air flow can be essential to controlling pollutants. The process of removing stale air and replacing with fresh can be mechanical (ductwork) or natural (air flow and natural stack effect.)

Two things can affect natural air flow: holes in walls and air-pressure difference (caused by wind or stack effect). The stack effect in a home is much like air movement in a chimney: piston-like flow of air from low part of house to high part (where the warm air escapes) and entry of cool house through the bottom of the house. However, wind and natural stack effect aren't enough to ensure a continuous supply of air, and that's where ductwork comes in.

	Ventilation system ductwork
	Figure A
	Figure B

Ductwork

Ductwork is a mechanical system that distributes air through all rooms. It requires low levels of ventilation air (15 cubic feet of air - or CFM - discharged per minute). The system can be controlled by homeowner and can filter pollutants.

• Can be installed inside walls, ceilings or floors.

• Are either round or rectangular.

• Older ducts are made of rigid galvanized steel or aluminum.

• Most ducts today are multi-layer, insulated, flexible sleeves lined with plastic or foil.

• Ducts carrying cold air need to be well-insulated to prevent condensation and the resulting moisture build-up (leading to mold).

• The joints and sections of ductwork can be susceptible to leaks, which can pollute air, disrupt air pressure and draw radon gas into the house. To properly seal, avoid the use of common duct tape. In a heated and cooled area, it will dry and crack. Use mastic or mastic tape. Apply mastic across seam to create seal (figure A), then apply mastic tape and use brayer or squeegee to press the tape tightly against the surface (figure B).

Improving air flow:

• Placing a exhaust fan in a window or attic will draw stale air out of the house, and create negative pressure to draw fresh air into the house.

• Small grilles in the exterior walls can serve as fresh air intakes.

• A window supply fan can blow fresh air into the house or apartment. Both exhaust and supply fans can be used in tandem, as long as both are equal capacity.

Did you know? As many as 2,000,000 dust mites can live in your mattress. Vacuum mattresses regularly and replace every few years.

RESOURCES :

Health House Consumer Information
American Lung Association
Web site: www.healthhouse.org