Methods of Estimating Air Infiltration through Windows

The mechanism of air infiltration is reviewed as background for introducing a procedure that yields more reliable estimates of average infiltration rates through a window unit than do methods currently employed. The procedure is applied to estimating the average winter heat losses through windows in low-rise residential buildings variously located throughout the United States. It is concluded that, regardless of climate, the heat loss attributable to infiltration through the window unit is small compared with that incurred as a result of direct transmission of heat through the window.