HOME & GARDEN CONSUMER GUIDE

Improving the Efficiency of Your Duct System

One of the most important systems in your home or small business, though it's hidden beneath your feet and over your head, may be wasting a lot of your energy dollars. Your duct system, a branching network of tubes in the walls, floors, and ceilings, carries the air from your furnace and central air conditioner to each room. Ducts are made of sheet metal, fiber glass, or other materials.

Unfortunately, many duct systems are poorly insulated or not insulated properly. Ducts that leak heated air into unheated spaces can add hundreds of dollars a year to your heating and cooling bills. Insulating ducts that are 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 unconditioned 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 be drawn into return ducts through unsealed joints. In the summer, hot attic air can be drawn in, increasing the load on the air conditioner. In the winter, your furnace will have to work longer to keep your house comfortable. Either way, your energy losses cost you money.

Although minor duct repairs are easy to accomplish, ducts in unconditioned spaces should be sealed and insulated by qualified professionals using the appropriate sealing materials. Here are a few simple tips to help with minor 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 Laboratories logo to avoid tape that degrades, cracks, and loses its bond with age.
  • 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.

Source U.S. Department of Energy