How Can External Hvac Ductwork Be Insulated?

To insulate your HVAC system, start by turning on your heating or cooling system and checking for air leaks along the ducts. Pay attention to any joints or connections in the ductwork and mark any air leaks. Turn off the furnace or attic air conditioner unit and repair ductwork leaks as they can account for 20% of the total cost of heating and cooling.

Exterior duct insulation can reduce HVAC system operating costs by controlling heat gain or loss through air duct walls and helping systems run more efficiently. It also absorbs noise generated by the ductwork. Rooftop ducts are particularly vulnerable to heat loss.

To insulate the exterior, choose between sleeve-style insulation and blanket wraps. Metallic foil tape is used to cover air leaks and is designed to seal ductwork. Standard cloth duct tape will not fix holes in HVAC ductwork.

Installation of Duct Insulation Wrap involves cutting the insulation wrap to “stretch out” dimensions, including the duct perimeter, plus extra to form an overlapping stapling and taping flap. Wrap the insulation around the duct’s perimeter, with the facing out, tightly butt the adjacent sections with the overlapping flap. Straighten the duct as much as possible to reduce air resistance.

Fibrous glass insulation boards are also available for application to the outside of sealed sheet metal ducts, housings, and plenums. Most exterior ducts are wrapped with sheets of fiberglass insulation with an exterior jacket of aluminum wrap, venture clad, or other weather-resistant material. When insulating HVAC ductwork, use foil-faced fiberglass insulation with an R-6 or higher R-value to block radiant heat transfer.

For exterior ductwork, closed cell insulation like high-quality phenolic is recommended. First, seal all metal duct work with metal foil tape and then apply waterproof mastic over the top to make the ducts more air-efficient.