Silicone Vapor Shield underlayment for hardwood flooring. It has been tested under various conditions for its permeability and effectiveness for protecting hardwood floors from subfloor moisture. Silicone Vapor Shield is made of 6 mil. wet-strength paper and has a baked-on silicone coating. It won’t easily tear apart during installation. It is suitable for use on radiant heated floors. 400 ft² roll.