Air Infiltration

Air Infiltration is the rate at which air passes through joints in the window. Heat loss and gain occur by air leakage through cracks in the window assembly.


Air Infiltration

Outside air infiltrating to the inside of your home.

Our Window’s Defense


Weather-stripping: Dual and triple weather-stripping is run along our window’s openings to minimize air leakage.


Window Design: Crank-Out windows have the least amount of air leakage of all our operable windows. A high sill dam leg reduces water and air infiltration on up & down windows.


No Weep Holes: Most up and down windows have horizontally drilled holes at the bottom sill to let water out. Our window doesn't. This is because virtually no water gets into our window frame. Weep holes can also let air inside the window. No weep holes—no place for air to infiltrate.


Air Infiltration Numbers

Air Infiltration is measured in cubic feet of air passing through one square foot of window area per minute. The lower the Air Infiltration value, the less air will pass through joints in the window. Industry standards and most building codes require an Air Infiltration number of .30. Our Up & Down Windows perform 36.7% better than industry standards.

Buyer Beware of Low Air Infiltration Numbers:

Considerably lower Air Infiltration numbers can be very misleading. As the tested window size can be very small. A smaller window will have less air infiltration and might not represent the window and related air infiltration you will be receiving. Our tested windows are very large. Hence, if you get a smaller window, the Air Infiltration number will not be misleading. Tested sizes: Up & Down: 44” x 66”, Sliding: 69” x 48”, Crank-Out (casement): 36” x 76”.