Housewrap, also known by the genericized trademark homewrap, generally denotes a modern synthetic material used to protect buildings. Housewrap functions as a water-resistant layer, preventing rain or snow from getting into the wall assembly while allowing water vapor to pass to the exterior. Housewraps can only be exposed for a few months, as it is not a weather resistant layer, and weather elements including sunlight and temperature, can damage it. Furthermore housewraps are not a form of insulation. If moisture from either direction is allowed to build up within stud or cavity walls, mold and rot can set in and fiberglass or cellulose insulation will lose its R-value because of the heat-conducting moisture. House wrap may also serve as an air barrier if it is sealed carefully at seams and supported to resist wind loads.