Duct insulation used in a conditioned attic, should be 2″ thick fiber glass or rock wool with a minimum density of .6 pounds per cubic foot. For the purpose of this question assume a heating location of 8002 degree days.

Duct insulation used in a conditioned attic, should be 2″ thick fiber glass or rock wool with a minimum density of .6 pounds per cubic foot. For the purpose of this question assume a heating location of 8002 degree days.