Atlas EnergyShield Ply Pro is a high performance insulation panel composed of a glass faced closed cell polyisocyanurate foam core bonded to 5â„8ʺor 3/4ʺ fire treated plywood. It is designed to be a component of commercial wall assemblies requiring a Class A, NFPA 285 compliant (TER 1306-03), continuous insulation. This product has been validated by UL Environment as resistant to mold growth based on independent testing to UL 2824.