AirOutshield Roof is a breathable roofing underlayment that is composed of a multi-layer, spun bonded polypropylene.  AirOutshield™ Roof is used as a secondary drainage plane under the roofing systems including metal, copper, zinc, slate, cedar, clay tile and other systems that require an underlayment.  AirOutshield with its rated 119 Perm rating is the leading breathable roof underlayment. The high breathability allows moisture within the roof system to dry rapidly. Thus, reducing potential for mold, mildew, rot and corrosion.