THERMAX™ Heavy Duty Insulation consists of a glass-fiber-reinforced polyisocyanurate foam core faced with nominal 4 mil embossed white thermoset-coated aluminum on one side and 1.25 mil embossed aluminum on the other. It can be installed exposed to the interior without a thermal barrier. THERMAX™ Heavy Duty offers high, long-term R-value. The facers help prevent water and water vapor intrusion into the insulation foam, and allow the foam to stabilize at a higher R-value. Used in conjunction with the appropriate joint closure system for the application, THERMAX™ Heavy Duty Insulation with its low perm rating helps to reduce moisture condensation within and behind the insulation.