How Professionals Seal Air Duct Leaks (And Why Duct Tape Fails)

Despite the name, fabric-backed duct tape dries out, loses adhesion, and falls off within a year or two — especially in attics where heat cycles are extreme.

Mastic for joints and seams, foil-backed UL-181 tape for sheet-metal seams, and mechanical fasteners on flex-to-collar connections. All three together create a permanent seal.

After sealing, a real repair is verified — either with a duct blaster, a manometer, or visual smoke testing — to confirm the leak is actually closed and not just covered.