How to Insulate a Basement's Ductwork

Shelley Frost

Ductwork often travels through the basement to carry the conditioned air from your heating and cooling system throughout the home. Unless the basement is finished, that ductwork is likely exposed in an area that isn't directly heated and cooled by the system.

Bare ductwork often causes loss of conditioned air.

Some of the conditioned air is often lost as it is conducted through the metal ducts. The joints in the ductwork and any cracks or holes in the pipes give the air additional escape routes, making your heating and cooling system work harder. Insulation helps reduce the amount of conditioned air that escapes into the basement.

  1. Inspect all of the exposed ductwork in the basement to look for loose connections, cracks or damage. Tighten the ductwork at the joints as needed. Replace sections of the ductwork that are damaged.

  2. Tape around all of the visible joints with foil tape. The specialty tape is designed to withstand the heat that flows through the ducts and holds up better than regular duct tape. Duct mastic is another option for sealing the joints. Apply the mastic to the joints and allow it to dry.

  3. Place the duct wrap insulation around the ductwork. Choose duct insulation of at least R-6 for the R-value, which is a measurement to show how well the insulation prevents heat from traveling through it. Install long sections of the insulation on the straight runs of ductwork, using fiberglass tape to hold it in place around the ducts.

  4. Cut the longer pieces of insulation using a utility knife to make it fit on smaller stretches of ductwork. Piece together the insulation to fit the space.

  5. Tape the slits with fiberglass tape to keep the insulation secure and to reduce any residual air loss. Tape the individual sections together to create a solid insulating barrier along the ductwork.

  6. Tip

    If you plan to replace your ductwork, you have the option of purchasing ducts that are already insulated to save you time.