Thermax™ Sheathing is a non-structural, rigid board insulation consisting of a glass-fiber-infused polyisocyanurate foam core laminated between 1.0 mil smooth, reflective aluminum facers on both sides. The glass-fiber reinforcement contributes to improved fire performance and dimensional stability. In the USA THERMAX™ Sheathing can be installed exposed to the interior without a thermal barrier. In Canadian construction Thermax™ exposed to the interior must be covered with a thermal barrier.