One of the most important systems in your home, though it’s hidden beneath your feet and over your head, may 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.

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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 the ducts that are in unconditioned spaces is usually very cost-effective. If you’re having a new duct system installed, consider one that comes with insulation already applied.

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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 crawlspace. If the supply ducts are leaking, heated or cooled air can be lost by being forced out of unsealed joints. 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 workload 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 make, ducts in unconditioned spaces should be sealed and insulated by qualified professionals using appropriate sealing materials.

Duct Tips

The following 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 tape to seal your ducts, avoid cloth-backed, rubber adhesive duct tape, which tends to fail quickly. Researchers recommend other products to seal ducts: mastic, butyl tape, foil tape, and other heat-approved tapes. Look for tape with the Underwriters Laboratories logo.
  • 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. Water pipes and drains in unconditioned spaces could freeze and burst if the heat ducts are fully insulated because there would be no heat source to prevent the space from freezing in cold weather. However, using an electric heating tape wrap on the pipes can prevent this. Check with a professional contractor.

Ducts: Out of Sight, Out of Mind

The unsealed ducts in your attic and crawlspace lose air, and uninsulated ducts lose heat, wasting energy and money.

  • If your basement has been converted to a living area, hire a professional to 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.
  • When doing ductwork, be sure to get professional help. Changes and repairs to a duct system should always be performed by a qualified technician.
  • Ducts that don’t work properly can create serious, life-threatening carbon monoxide (CO) problems in the home. If you have a fuel-burning furnace, stove or other appliance, or an attached garage, install a CO monitor to alert you to harmful CO levels.

Long-Term Savings Tip

  • If your ducts aren’t insulated and travel through unheated spaces, such as the attic or crawlspace, you can lose up to 60% of your heated air before it reaches the register. Get a qualified professional to help you insulate and repair ducts.