Permavent METAL 490g is a condensation and control and drainage system, for fully supported standing seam and metal roofing applications.Permavent use the very latest technology from the medical industry to encapsulate the highest grade hydrophobic film inside the very highest quality spunbond polypropylene layers. Permavent membranes are manufactured in a single process that greatly improves the quality and integrity of our membranes. This 3 in 1 process means that Permavent offer superior strength, breathability, flexibility and durability.