How to Insulate a Metal Duct


If you have metal heating and/or air-conditioning ducts in your home that aren't insulated, they are probably costing you energy dollars. The exception is ducts that are installed in areas of your house that are properly insulated. Otherwise, the metal ducts are leaking heat and/or cooled air. To remedy this problem and save yourself money, you'll need to add insulation to the metal ducts. The insulation will help contain the heat and/or cooled air within the ducts so it can reach its intended destinations and heat or cool your home better.

Things You'll Need

  • Work gloves
  • Safety goggles
  • Dust mask
  • Ladder, possibly
  • Old rag
  • Metal duct tape
  • Scissors
  • Measuring tape
  • Insulation
  • Duct tape
  • Put on work gloves, safety goggles and dust mask to protect yourself while you work. Set up a ladder to reach the ducts, if necessary.

  • Seal all the connecting seams of the metal duct with metal duct tape. Wipe the first seam off with a rag to remove dirt and debris.

  • Unroll the tape around the diameter of the duct to determine how long the first piece needs to be. Cut the tape to the desired length with a pair of sharp scissors.

  • Peel off the protective backing on the back of the metal duct tape. Position the end of the tape so its center straddles the center of the seam. Apply the tape to the seam and press it down to release air bubbles. Seal the remaining seams.

  • Measure the diameter of the duct with a measuring tape; add 2 inches. Measure and cut a piece of insulation to that size.

  • Wrap the insulation so the vapor barrier faces away from the ducts. Wrap it snugly. Secure the end with duct tape.

  • Measure and cut the next piece of insulation. Wrap it around the next section of duct so it overlaps the first piece by a couple inches. Secure the piece into place. Continue insulating the remaining ducts in the same manner.

  • Finish the project by taping the seams where the pieces of insulation overlap each other with duct tape.

Tips & Warnings

  • Remove any existing duct insulation before you begin this task.

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  • Photo Credit Hemera Technologies/ Images
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