How to Seal Leaky Ductwork

The Problem

Leaky ducts waste 20-30% of heated or cooled air. Your system runs longer, costs more, and rooms stay uncomfortable.

Turn the system on and feel along duct joints in the attic, basement, or crawlspace. You'll feel air escaping at connections.

Clean the duct surface with a damp cloth
Apply mastic sealant (not duct tape — it fails in months) to every joint and seam
Wrap joints with foil-backed tape over the mastic
Insulate exposed ducts in unconditioned spaces with R-6 duct insulation

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