One motto of the high-performance home industry is, “Build it Tight, Ventilate Right.” The idea here is to minimize or eliminate uncontrolled air infiltration from undesirable locations, such as from attics, garages, crawlspaces, or through wall insulation.
Then, provide just enough fresh make-up air from known, clean locations to remove humidity from human activities (cooking, showers, breathing, etc.), and other pollutants, such as household chemicals, cooking odors, materials off-gassing, etc. When standards for fresh air ventilation are followed, indoor air quality is maintained, while not over-ventilating which would detract from energy performance.
The alternative to “Build it Tight, Ventilate Right” is to design a home to leak. This is as impractical and ineffective as it sounds. The leakage rate of a home varies widely over time, as it is influenced by wind speed and direction, seasonal temperature variations and usage of household venting appliances (range hoods, clothes dryers, gas furnaces, fireplaces, exhaust fans, etc.). So, at times the house may leak too much, wasting energy and causing discomfort, while at other times may not leak enough, with possible humidity and pollutant build-up. And when it does leak, the air that enters the house is of dubious quality.
So, we have debunked the myth that houses need to breathe. We know how to build homes that work well. It’s not that hard, it doesn’t cost that much more, and the homeowner is a clear winner.
By: Gary Kahanak, HERS Rater