How to Seal Leaky Ductwork | Ask This Old House

Richard Trethewey shows an innovative new way to seal ducts from the inside. (See below for steps.)
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Steps for How to Seal Leaky Ductwork:
1. Remove the grilles from all of the supply and return registers.
2. Plug each duct register with foam rubber and wide strips of tape.
3. Pressurize the duct system with a blower fan.
4. Use a computer to analyze the data to determine the amount of air leaking from the ducts.
5. Use the blower fan to mist the inside of all the dust with liquid-rubber sealant.
6. The sealant will find and plug all air-leaking holes, cracks, and seams.
7. After applying the sealant, run another pressurized blower test to verify the improved results.

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Homeowners have a virtual truckload of questions for us on smaller projects, and we’re ready to answer. Ask This Old House solves the steady stream of home improvement problems faced by our viewers—and we make house calls! Ask This Old House features some familiar faces from This Old House, including Kevin O’Connor, general contractor Tom Silva, plumbing and heating expert Richard Trethewey, and landscape contractor Roger Cook.

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How to Seal Leaky Ductwork | Ask This Old House

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