Overview

For compliance with energy code requirements to control whole-building air leakage and to protect assemblies from the potential damaging effects of moist air intrusion, it is necessary to consider and air barrier strategy for your building walls and the building as a whole. Controlling air leakage around windows also lessen the effect of pressure differentials at window-to-WRB flashing interfaces such that water leakage risk is reduced. 

Like continuous insulation and the WRB system, an air barrier system must also be continuous to be effective. This means seal the air leaks, joints, interfaces with various components that penetrate the wall, and at interfaces between the wall and other building assemblies (e.g., floors, roofs, and foundation).

Modern energy code requirements for residential and commercial construction provide a detailed list of air barrier and air sealing requirements. For one- and two-family dwelling construction per the IECC-R provisions also require that blow-door testing be conducted as a means to confirm maximum whole building air leakage requirements are not exceeded (e.g., 5 ACH in Climate Zones 1 and 2; 3 ACH in Climate Zones 3-8; where ACH is the building’s air changes per hour at a 50 Pascal pressure differential).

There are many choices for air barrier materials and methods and also the location of the air barrier. One of these material choices is to use the FPIS-ci as an air-barrier on the exterior side of the assembly. This is particularly efficient when the FPIS-ci is also used as the WRB since this would require all joints to be sealed. 

DESIGN RESOURCES: For a review of air barrier options and practical design and installation guidance, refer to the following series of articles published in Energy Efficiency and Building Science News feed:

Also refer to Air Barrier resources. 

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