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. Moreover, unlike other companies, who simply stick the different layers together, Permavent membranes are manufactured in a single process that greatly improves the quality and integrity of our membranes. Additionally, this 3 in 1 process means that Permavent offer the best performing breather membranes in their class with superior strength, breathability, flexibility and durability.