The main purpose of an air barrier system is to protect the building structure and the insulation from moisture damage. It must resist air movement; be continuous, completely surrounding the envelope of the house; be properly supported by rigid surfaces on both the interior and exterior (to prevent movement in high winds); and be strong and durable. Attention to detail during installation is critical for good performance.

Various materials throughout the envelope act as an air barrier. Large-surface building materials such as drywall, baseboards or structural members and windows and doorframes are incorporated into the air barrier by sealing them to the adjoining materials. Caulking, tapes and gaskets are used for joints between materials that do not move, and weatherstripping, for joints that do move.