Will New Windows Have Air Leakage?
Any operable window or door, even new ones, will have some degree of air-filtration. All windows are tested under the influence of a 25 MPH wind under which the air infiltration rate must be less than 0.30 cubic feet of air per minute per square foot of window area. Therefore, a 3 foot by 4 foot window can have a total air infiltration of 3.6 CFM. At a 50 MPH wind, the wind pressure is four times greater than it is at 25 MPH. As a result, considerably more leakage will occur at higher wind speeds.
Most new windows will have an air infiltration rate below the 0.30 maximum. However, a number of factors such as window size, location, building design and terrain, just to name a few will affect a windows air infiltration performance.