Certainteed 416.5 sq. ft. Continuous Air Barrier and Smart Retarder 50 ft. L x 8 ft. WCertainTeed MemBrain Air Barrier and Smart Vapor Retarder is the go to solution for your home or business when you need to keep the wall cavity dry. MemBrain's technology helps prevent mold, which is unlike traditional vapor retarders that can't adapt and sense humidity changes. The advanced sensing feature of this MemBrain vapor barrier allows it to adjust permeance to varying humidity throughout the year. In the winter, the CertainTeed air barrier