This Imperial Duct Insulation Sleeve works as an energy efficient insulation blanket suitable for heating, ventilation, and air conditioning systems. Specifically designed to insulate rigid or semi-rigid round ducts, it is an excellent method for reducing heat or cool loss and condensation build-up. The sleeve is made of a thick fiberglass insulation blanket enclosed in a strong, fiberglass-reinforced silver metalized outer jacket. Check your local building codes prior to installation.