This lightweight thermal insulation board composed of a closed-cell polyisocyanurate (polyiso) foam core bonded to reinforced aluminum facers with clear coating for limited protection against oxidation on each side. Rmax Thermasheath® is suitable for use on the exterior side of existing ductwork. When the ductwork is solely on the exterior of the building, the insulation need only be protected from the outside weather conditions. As an example, this can be done with a waterproofing membrane installed per the manufacturer’s recommendations.