| Resistance to air leakage is a key requirement of an air barrier system. The Institute for Research in Construction (IRC) of the National Research Council Canada has proposed the following levels of airtightness for air barrier systems:
Air Leakage Classification Air Leakage Rate (l/s-m2 @ 75 Pa)
Type 1 0.10 to < 0.15
Type 2 0.05 to < 0.10
Type 3 < 0.05
In order to create an air barrier system that achieves the required overall air leakage rate, it is important that the materials composing the air barrier system be resistant to air leakage. In order to select materials to use in constructing an air barrier system that will meet the above guidelines, the designer needs to know the air leakage rates of building materials. This research project was conducted to give designers guidance in choosing materials appropriate for air barrier systems.
Since this study was conducted, the National Building Code (NBC) has been amended to require that materials forming part of an air barrier assembly should not exceed an air leakage rate of 0.02 l/s-m2 @ 75 Pa. | 
