DIY Projects

How to Repair Leaks in HVAC Ductwork

By: Danny Lipford

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

Print   Video Transcript

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.


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One Comment on “How to Repair Leaks in HVAC Ductwork”

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  • daniel w hebert Says:
    March 14th, 2017 at 8:52 am

    what is an RAPP boot? I have this notes on a set of specs.
    what do you recommend for lighting rods which penetrate a metal roof?

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How to Repair Leaks in HVAC Ductwork