Klober Permo Ecovent Roofing Felt - 50m x 1.1m Description A lightweight vapour-permeable roofing underlay suitable for warm and cold pitched roofs. Permo Ecovent is a laminated sheet material, with outer layers of polypropylene, and a inner layer of polyethylene. Features Lightweight vapour permeable roofing underlay. Three-layer material. BBA approved for non-ventilated cold and warm roofs. No additional ventilation required. UV stable for four months. Allows the roof structure to breathe yet fully waterproof. Type LR underlay. Limits air leakage in a sealed roof application.