An air barrier is a continuous layer of material or assembly designed to prevent uncontrolled air leakage between conditioned and unconditioned spaces. Air barriers are critical components in building envelopes, reducing energy loss and improving occupant comfort. They work in conjunction with insulation to create a complete thermal boundary.
Material Specifications
Effective air barriers include materials such as rigid foam sheathing, spray polyurethane foam, and specialized membranes with permeance ratings below 0.1 perms. These materials must maintain integrity at seams and penetrations, with sealed joints typically achieving air leakage rates below 0.06 cfm/ft² at 75 pascals pressure differential according to ASTM E2357 standards.
Installation and Performance
Proper installation requires continuous coverage across all building surfaces, including careful sealing around windows, doors, and mechanical penetrations. When properly executed, air barriers can reduce heating and cooling loads by 10 to 20 percent, significantly lowering energy consumption and utility costs over the building’s lifetime.