How to Reseal HVAC Flexible Ducts

Turn on the unit and place a ladder under the attic access if applicable. To detect hard-to-find leaks, closing all the air registers increases air pressure in the ducts making them easier to locate.

Enter the attic and inspect all the flexible duct connections for leaks with the aid of a flashlight. Flexible ducts connect to collars attached to plenums, connectors that join the flexible duct together and air registers installed in the ceilings of most rooms.

Cut the plastic tie that secures the flexible duct insulation and vapor barrier to the metal collar or connector using a razor knife. Peel back the material about 12 inches to expose the plastic and metal coil duct and to allow ample room to make the repair.

Inspect the connection where the duct and collar join. Run your hand around the connection to detect any leaking air.

Remove damaged metal duct tape from around flexible duct connections. Reposition the duct over the collar leaving about 1 inch of the metal collar exposed for duct tape attachment.

Wrap the flexible duct and metal collar or connector with metal duct tape to seal the joint. Pull the vapor barrier and insulation back in position around the connection and secure with a plastic tie.