How to Seal Vent Ducts With Caulking

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Things You'll Need

  • Duct sealant caulking

  • Caulk gun

  • Utility knife

  • Paper towel

  • Damp cloth

  • Foam brush

Ducts in your home, such as those used for heating and cooling, can develop leaks or may require sealing when they are installed. Air leaks that occur in vent ducts must be sealed not only to prevent air from escaping from the system but to save money on energy bills as well. One way to seal vent ducts is to apply caulking to fill in gaps. You can seal vent ducts with caulking by first examining the vent ducts for leaks or gaps.


Step 1

Cut the end off a tube of a duct sealant caulk with a utility knife.

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Step 2

Place the tube of duct sealant caulk in the caulking gun.

Step 3

Press the trigger on the caulking gun to move the push plate tight against the tube.

Step 4

Clean the surface of the vent duct with a damp cloth to remove any dirt and residue.

Step 5

Run a bead of caulk along the length of the leak, such as a joint. Press the trigger on the caulk gun to force the caulk out of the tube, and let off the trigger to make it stop.


Step 6

Spread and smooth out the caulk over the area of the leak and into the joints by using a foam brush. You can also use the foam brush to remove any excess caulk.

Step 7

Wipe off any excess caulk from the brush or your hands with a piece of paper towel.

Step 8

Repeat steps 3, 4 and 5 to seal the vent duct wherever there is a leak.


Use your finger to smooth out the caulk if you do not have a foam brush handy.


Too little caulk will come out of the tube if you did not cut enough off the tip.


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