Air barriers have become an integral part of the design in wall assemblies over the last 15 years. Air barriers can be used over any substrate and behind any cladding. An air barrier can be either a building wrap, self-adhesive membrane or fluid applied packaged in a 5 gallon pail or 55 gallon drum. Building wraps and self-adhesive membranes have been used for over 25 years as substrate protection. Building paper often incorporates a self-adhesive membrane at transitions, window and door openings and substrate penetrations. Self-adhesive membranes are installed over the entire substrate including transitions, window and door openings and substrate penetrations. Some fluid applied air barriers were initially designed to function as substrate protection and as a component of a drainage EIF system.
As the demand increased for building a more energy efficient building envelope, air barriers became a product that could be used to protect the substrate regardless of the type of cladding on the exterior. The use of one continuous air barrier as substrate protection simplified the specification and design process. Air barriers provide protection against moisture intrusion, water leakage, mold and mildew. One major difference between building wraps, self-adhesive membranes and a fluid applied air barrier is performance. Air barriers, depending on the type and manufacturer, can be exposed to the elements for up to six months without a significant change in water penetration resistance. Air barriers are considered the weatherproof layer and the cladding is the decorative feature.