Sheet metal ducts shall be clean, dry and sealed tightly prior to insulating with CertainTeed Marine Duct Wrap. To ensure installed thermal performance, CertainTeed Marine Duct Wrap shall be cut to "stretch-out" dimensions. This requires measurement of the duct perimeter, then cutting the duct wrap to the dimensions (perimeter + add-on) indicated in the stretch-out table on the Marine Duct Wrap Insulation specification sheet (30-35-015). A 2" piece of insulation is removed from the facing at the end of the piece of insulation to form an overlapping stapling and taping flap. CertainTeed Marine Duct Wrap is installed by wrapping the insulation around the perimeter of the duct with the facing out. Adjacent sections of duct wrap are tightly butted with the 2" taping flap overlapping. Seams shall be stapled with outward-clinching staples on approximately 6" centers. Where a vapor retarder is required, all seams, joints, tears, punctures and/or other penetrations of the duct wrap shall be sealed with a pressure-sensitive vapor retarder tape that matches the facing, or a suitable mastic system. Where rectangular ducts are 24" in width or greater, CertainTeed Marine Duct Wrap shall be additionally secured to the bottom of the duct with mechanical fasteners spaced 18" on center to prevent sagging. For additional installation details, consult the National Commercial and Industrial Insulation Standards (current edition) published by the Midwest Insulation Contractors Association (MICA).
CertainTeed recommends that all installations be approved and certified by the local approval bodies. Approved assemblies for specific fire rating are available upon request.