Where to Add Insulaion

Once you've air-sealed the attic, be sure insulation meets DOE standard. The standard for most of the U.S. is R-38. Call the Energy Efficiency and Renewable Energy clearinghouse (800-363-3732) for the recommendation for your area.

If you need to add more insulation on top of the old, use unfaced batts or loose fill. Owens Corning and Johns Manville make a batt encased in plastic for easy handling.

You can also reduce heat loss by insulating over light fixtures in the rooms below your attic — provided you replace the standard recessed versions with fixtures rated "IC," for insulated ceiling. To prevent airflow, buy IC fixtures that also have an air- and moisture-tight housing. They're available from most major lighting companies. Halo also offers an airtight retrofit collar for its IC fixtures.

Detecting Duct Leaks
Leaky ductwork in a forced-air heating and cooling system creates several problems. A supply duct that leaks into an attic or crawl space pours cooled or heated air — and the money you paid for it — into the void. Leaky return ducts pull hot or cold attic or crawl space air into the system. Indeed, a duct that runs through the attic can pull in 140F air in summer, making the cooling system work that much harder. It also pulls in dust, moisture, mold, and other contaminates.

Start by reconnecting any ducts that have fallen apart. Then hunt for holes in supply ducts by feeling for the air as it leaks out and seeing if a tissue clings to return ducts as air is sucked in. Use duct mastic (available in cans or caulking tubes) to seal small gaps. For larger ones, reinforce the mastic with fiberglass mesh tape. You can also use UL-181 aluminum tape — essentially professional duct tape. Just don't use the cloth variety labeled duct tape, which really isn't for ducts.

Return and supply ducts should also be pressure-balanced for forced-air systems to work efficiently. Leaks upset that balance, and can drive heated or cooled air out of the house or pull outside air in. Unfortunately, sealing only some of the leaks can do the same thing. Have the system inspected by a pro when you're done to be sure you didn't miss any.

After the ducts are sealed, be sure any that run through unconditioned crawl spaces, basements, or attics also are insulated. Insulating long runs of ductwork is best left to a contractor. But you can handle short runs yourself with foil-faced fiberglass duct insulation. Cover all sides and secure the insulation with a cable tie.

Note: Have a pro perform a backdraft test before and after you work on the ducts.

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