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How To Seal Air Ducts With Mastic – Seal Leaky Air Ducts & Save Energy

step-a

A  CLEAN DUCT SURFACE

Use a cloth to wipe dirt, dust, and debris from the surface of the duct. If oil or grease is present, wipe clean with a damp cloth.

step-c
step-b

B  JOINTS WITH LESS THAN ¼ INCH GAPS

Coat the entire joint with a 2” wide by 1/16 of an inch thick continuous strip of mastic, using the end of the brush to work the mastic into the joint.

C  JOINTS WITH GAPS GREATER THAN ¼ INCH

Reinforce with RCD Corporation’s Glasscoat (fiberglass mesh) in addition to mastic. Apply a coat of mastic per (B) above, then embed Glasscoat into this first coat of mastic and finish by applying a second coat of mastic filling the mesh entirely.