Better control of infiltration losses offers an opportunity for substantial energy savings. The ASHRAE Handbook: Fundamentals Volume presents two methods for estimating infiltration. The air change method is a gross estimate based on the number of windows and doors in each room. The crack method based on measurements of flow through the cracks around windows and doors accounts for crack size and the effect of weather.

Comparisons of tracer gas measurements with calculations by both the air change and crack methods are presented for test houses in California and Minnesota. Agreement is adequate for sizing equipment but not for assessing indoor pollution problems.