A high performing, resilient PIR insulation board for use in warm flat roofs under built-up felt and single-ply waterproofing systems. Plylok consists of an insulation board bonded to a 6mm plywood top layer and boasts high compression strength, dimensional stability and consistent board sizes. Plylok is an insulation board with a core of rigid polyisocyanurate foam faced on both sides with a bright, gas tight and multi-layered complex of kraft and metal foil with a 6mm WBP laminated to the top side. Manufactured using a blowing agent with zero ODP