How to Repair Leaks in A/C Ductwork

Leaks in HVAC ductwork allow air from your furnace or air conditioner to escape.

That’s a problem because it wastes energy and raises your home’s heating and cooling costs.

Fortunately, fixing this problem couldn’t be easier, and it requires minimal expense.

Here’s how to seal holes or tears in ductwork:

Locate Leaks: Turn on the HVAC fan and touch the ductwork. Feel it up and down and check for drafts that indicate escaping air.

Seal Leaks: Turn off the fan and apply special metallic foil tape over the hole or gap. Don’t use standard duct tape, since the adhesive will come loose over time. Purchase the metallic foil tape that’s specifically made for ductwork repairs.

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.

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 paintbrush 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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