Air leakage characteristics of 192 new windows installed in new residential construction representative of those units commonly installed in the Minneapolis/St. Paul Metropolitan Area have been measured and evaluated. The tested windows represented all major operation types, window material types and manufacturers represented in this market segment.

The air leakage data obtained in the field were compared to industry and government standards and manufacturers reports for reference. Window operation type, manufacturer, installation, construction material and window defects were analyzed in detail to determine their effects on air leakage.

The results of the project indicate that the air leakage of installed windows can be significantly higher than might be expected from laboratory tests. Window operation type was the prime variable in explaining the air leakage performance.