M1601.4.6 Duct Insulation

Duct insulation shall be installed in accordance with the following requirements:

1. A vapor retarder having a permeance of not greater than 0.05 perm [2.87 ng/(s • m² • Pa)] in accordance with ASTM E96, or aluminum foil with a thickness of not less than 2 mils (0.05 mm), shall be installed on the exterior of insulation on cooling supply ducts that pass through unconditioned spaces conducive to condensation except where the insulation is spray polyurethane foam with a water vapor permeance of not greater than 3 perms per inch [1722 ng/(s • m² • Pa)] at the installed thickness.
2. Outdoor duct systems shall be protected against the elements.
3. Duct coverings shall not penetrate a fireblocked wall or floor.