- 1). Turn off power to your HVAC unit. If you try to seal your ducts with the HVAC unit on, the air will bubble through the caulk before it has a chance to cure.
- 2). Caulk all seams and joints on the duct work. Use duct sealing mastic that is dispensed with a caulk gun out of a caulk tube. Tool the caulk bead with a putty knife into the seam or joint to ensure adequate coverage.
- 3). Caulk around the duct plenum where it is attached to the HVAC unit. The duct plenum is the supply air duct that comes off the top of the HVAC unit.
- 4). Use foil tape in areas that you can't get a caulk gun into. It has an acrylic adhesive that will bond to the metal nicely. Don't use duct tape or any other cloth-backed tape. It will disintegrate over a very short time and allow your duct work to keep leaking.
- 5). Allow the caulk to cure for the specified time on the tube before turning the HVAC unit back on.
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