Discover RoofTopGuard® Breather: Consisting of nonwoven and film layers, the new breathable underlayment RKW RoofTopGuard Breather® is revolutionary thanks to its significantly higher permeability and water resistance as compared to other breathable products. RKW RoofTopGuard Breather® improves the indoor climate of buildings and helps reduce inside moisture in the roofing system that could cause mold, mildew, and expensive structural damage.