When air infiltrates through cracks in a fenestration products assembly, heat loss and gain can occur. The air leakage (AL) rating is expressed as the equivalent cubic feet of air passing through a square foot of the product's area (cfm/sq ft). The lower the AL, the less air infiltration.

 

For heavily trafficked buildings, air infiltration through doors is an important energy consideration. Revolving doors and double-doored entry ways should be considered in this case.

 

Window coverings are not effective at reducing air infiltration. Traditionally, the best way to eliminate drafts caused by infiltration is to caulk and weather strip windows, and doors as well.