Home Improvement Expert Danny Lipford

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How to Repair Leaks in HVAC Ductwork


Find out how to find and seal leaks in ductwork to save energy and lower your heating and cooling bills. Watch this video to find out how. ...More




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How to Repair Leaks in HVAC Ductwork

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Leaks in HVAC ducts allow air from your furnace or air conditioner to escape, wasting energy and raising heating and cooling costs.

To seal holes or tears in ductwork:

  1. Locate Leaks: Turn on the HVAC fan and feel along the ducts for drafts that indicate escaping air.
  2. Seal Leaks: Turn off the fan and apply special metallic foil tape made for repairing ducts over the hole or gap. Don’t use standard duct tape, since the adhesive will come loose over time.
  3. Apply Duct Mastic: Use a brush to apply duct mastic over the tape and joints to improve the seal.

Watch this video to find out more.

Further Information



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Leaks in ductwork are often found where lines branch off or separate. With the furnace fan running, you can feel air escaping the duct. Once you’ve found the leak, use foil duct tape to cover the gap and seal the leak.

For an extra layer of protection, use a paint brush to apply a coat of duct mastic. This thick, sticky material will dry to form an airtight seal that will keep the air in those ducts where it belongs.