8 ft. W X 100 ft. L Unfaced Air Barrier and Smart Vapor Retarder Roll 833 sq ft, Certainteed Membrain, Mfr#: 902008

For extra protection against moisture the MemBrain Continuous Air Barrier and Smart Vapor Retarder is your weapon of choice. It lets wall cavities dry out to help prevent mold. In summer when humidity is high it increases permeability so that moisture can escape as air tightness is maintained. In winter when humidity is low it continues to block moisture. Use MemBrain with un-faced insulation in place of kraft faced insulation or polyethylene. Not all climate zones require vapor retarders.