Field Studies of the Air Tightness of Residential Buildings

The heat loss (gain) due to air leakage becomes increasingly significant as more thermal insulation material or systems are added to a house to reduce the conductive heat loss (gain). It is quite clear that a standard energy procedure is needed whereby the housing industry and the energy agencies can practically evaluate or estimate the energy demand due to air leakage or infiltration for a new residential structure or a reinsulated existing house.

The two major techniques that have been utilized more recently to either quantify the air infiltration rate or characterize the air leakage of a house are the “tracer gas technique” and the “induced pressure technique.” The former can provide the absoluted air infiltration rate under various ambient conditions; whereas the latter can give an estimate on the relative air tightness of a house. Each one has its advantages or drawbacks in practice. However, they do compliment each other in situations where a large number of houses need to be measured.

A typical case is presented here to show that both techniques were applied to the same group of houses. The measured air infiltration rates from the tracer gas technique, and equivalent air leakage area from the induced pressure technique do show good agreement in concluding the air tightness of these houses. The existence of such air infiltration rate differences was also detected through the energy consumption test conducted among the same group. Some of the practical aspects of these two approaches are also presented.