Seal hidden energy leaks in ductwork
One of the most important systems in your home, though it’s hidden beneath your feet and over your head, might be wasting a lot of your energy dollars. Your home’s duct system, a branching network of tubes in the walls, floors, and ceilings, carries the air from your home’s furnace and central air conditioner to each room. Ducts are made of sheet metal, fiberglass or other materials.
Unfortunately, many duct systems are inadequately or improperly insulated. Ducts that leak heated air into unheated spaces can add hundreds of dollars a year to your heating and cooling bills. In fact, the average home’s duct system loses 30 percent of the hot or cold air that passes through it. However, insulating ducts in unconditioned spaces is usually very cost effective. If you are buying a new duct system, consider one that comes with insulation already installed.
Sealing your ducts to prevent leaks is even more important if the ducts are located in an area such as an attic or vented crawl space. If the supply ducts are leaking, heated or cooled air can be forced out unsealed joints and lost. In addition, unconditioned air can also be drawn into return ducts through unsealed joints. In the winter, your furnace will have to work longer to keep your house comfortable. In the summer, hot attic air can be drawn in, increasing the load on the air conditioner. Either way, your energy losses cost you money.
Here are a few simple tips to help with duct repairs:
Check your ducts for air leaks. First look for sections that should be joined but have separated and then look for obvious holes.
If you use duct tape to repair and seal your ducts, look for tape with the Underwriters Laboratory (UL) logo for the greatest durability. Unfortunately, duct tape tends to dry up, crack and lose its adhesion over time, especially in unheated spaces. On the other hand, mastic, a special paste, spreads easily and dries permanently, and is preferable for sealing joints and seams in metal ductwork.
All hot-air ducts passing through unheated spaces should be wrapped with insulation. You can use standard foil-faced fiberglass insulation, keeping the foil facing out; vinyl-faced insulation made especially for ducts; or rigid foam insulation. Use duct tape with standard fiberglass batts and rigid foam; with vinyl-faced duct insulation, use duct tape or double over and staple the seams.
Remember that insulating ducts in the basement will make the basement colder. If both the ducts and the basement walls are uninsulated, consider insulating both.
If your basement has been converted to a living area, install both supply and return registers in the basement rooms.
Be sure a well-sealed vapor barrier exists on the outside of the insulation on cooling ducts to prevent moisture buildup.
Get a professional to help you insulate and repair all ducts.
Sources: The U. S. Dept. of Energy and the American Council for an Energy-Efficient Economy. For additional information, log on to or www.aceee.org/consumer/consumer.htm.
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