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In this video, This Old House host Kevin O'Connor and energy auditor Paul Scheckel find and fix leaky heating ducts.


1. Tape over all the supply and return registers throughout the house.

2. Attach a duct blaster fan to a section of flexible duct, then attach opposite end of flexible duct to existing heating duct.

3. Use a pressure-and-flow gauge to determine air pressure in duct.

4. Blow smoke into the heating duct using a theatrical fog machine; check for smoke leaking out of the duct.

5. Hold a smoke pencil close to joints and seams in duct to determine if air is leaking out.

6. Don rubber gloves, then force duct sealant into leaky duct joints.

7. Remove any cloth-backed utility tape stuck to ductwork, and replace it with foil-faced duct tape.

8. Wrap all ducts with R-6 foil-faced fiberglass insulation; seal joints with foil-faced duct tape.