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posted: 5/11/2013 4:00 AM

Insulating ductwork pays dividends

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By Dwight Barnett

Q. I had a home-energy analysis. The report said my ductwork needs to be repaired upstairs and in the crawl space because that is where a good deal of leakage is, and it also is bringing bad air pollutants from my crawl space into my home. It's been recommended that repairs be made with either mastic and tape, or foam, which is more expensive ($2,500). What should I do?

A. When the ductwork is located in an attic or crawl space, it is important to seal the ducts at every joint and seam. The air you are losing has either been heated or cooled at your expense.

What you are asking is: "Will the repairs save energy dollars?" And the answer is yes.

The next question would be: "Will the costs to make the repairs result in some future savings spent on energy?" The answer is, in most cases, yes. Sealing the ducts is also a comfort issue in that all the air being forced through the ducts by the furnace fan will eventually reach each room that has a register.

Use either the metallic tape or the duct mastic recommended by the contractor. Traditional duct tape does not work well on ductwork. You can do this repair yourself if close, confined spaces such as the attic and crawl space do not cause you any problems. It's simply a matter of cleaning each surface area to be sealed before applying the tape or mastic.

The costs of the material, usually less than $200, will be minimal to the savings you can expect. In the attic and crawl space, you can insulate the duct using a fire-resistant fiberglass insulation with a reflective foil cover. The foam, while expensive, will both insulate and air seal the ducts, taking the place of the tape or mastic.

• Dwight Barnett is a certified master inspector with the American Society of Home Inspectors. Write to him with home improvement questions at C. Dwight Barnett at

Scripps Howard News Service

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