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Do Leaky Ducts Equal High Electric Bills?

Published on: May 14, 2013

After upgrading to a new heating and cooling system, it’s natural to expect improved performance and enhanced efficiency. If you’re disappointed with the results, other issues may be to blame. You’ve eliminated the system itself as the problem, so you should turn your attention to the ductwork in your home. Damaged and poorly designed ducts can dramatically reduce the efficiency of even the best HVAC system, which can lead to high electric bills and other problems.

Ducts: The Basics

Like most people, you probably have a basic understanding of how ducts work. Their primary function is to deliver conditioned air throughout the home. They are usually out of sight, so it’s easy to take them for granted. Assuming that they are up to par is a big mistake. If your energy bills seem to creep up month after month and you’re certain that your HVAC system is designed well and installed properly, it’s well worth it to take a closer look at the ducts.

Location of Ducts

The location of the ducts in your home has a major impact on how much they impact the cost of your energy bills. If your ducts are primarily in the basement or in other conditioned parts of the home, the amount of energy they lose may be negligible. If they’re located in attics, crawlspaces and other unconditioned areas, which is often the case, they could be reducing the efficiency of your heating and cooling system by as much as 25 to 40 percent.

Design of Ductwork

Chances are that the ducts in your home are made out of sheet metal. However, they are sometimes made out of plastic and wire composite, fiberglass board or other materials. There may be small benefits associated with specific materials, but the most important thing is that the ducts are properly insulated and sealed. As long as that’s the case, they shouldn’t have too negative of an impact on the efficiency of the HVAC system.

Supply and Return Ducts

For maximum efficiency, heated and cooled air should be moved through a home via a system of supply ducts and return ducts. Some homes lack return ducts, though. If that’s the case with your home, your heating and cooling system may never operate at optimal efficiency. The fan, which is usually a part of the furnace, forces air through supply ducts that then blow air out of registers throughout the home. Return ducts deliver air back to the fan. Returning air is usually at least partially conditioned, so return ducts enhance the efficiency of a heating and cooling system by a considerable degree.

Energy Loss and Ductwork

There are several ways in which ducts can reduce the efficiency of a heating and cooling system. A few examples include:

  • Heat Conduction – When a furnace is being used to heat a home, the warm air that passes through heats up the duct walls. The heat in the walls then dissipates into unconditioned parts of the home, where it doesn’t do anyone any good.
  • Air Leakage – Air leakage is a major problem. It most commonly occurs due to gaps, cracks and holes in the ducts. Up to 30 percent of conditioned air may leak out in this way, and it typically ends up in unconditioned areas like attics and crawlspaces.
  • Pressure Deficiencies – As long as ducts are properly sealed and insulated – and assuming there are supply and return ducts – they help to maintain balanced pressure that ensures optimal efficiency. Air naturally wants to travel from areas of high pressure to low pressure. For it to flow properly from supply ducts into rooms, for instance, the air inside the supply ducts must be higher in pressure. In order to move from rooms into return ducts, the air in the return ducts must be lower in pressure.

Design Flaws in Ductwork

Poorly designed ducts can wreak major havoc on the cost of heating and cooling a home. Consider these problems:

  • Leaks in Supply and Return Ducts – When supply ducts are airtight and return ducts leak, cold air from outside the home is drawn in due to the low pressure that is created. When return ducts are airtight and supply ducts leak, the same phenomenon occurs. In other words, all ducts must be as airtight as possible for optimal efficiency.
  • Uninsulated Ducts – All ducts should be properly insulated to ensure superior efficiency.
  • Unsealed Joints – Where two ducts meet, they must be sealed well.
  • Pipes – In unconditioned spaces near ducts, pipes may have gaps around them. This can affect the efficiency of the ducts, so such gaps should be sealed.
  • Ducts that Lead Nowhere – In some cases, there may be ducts that don’t lead to registers. They basically deliver heated and cooled air to unwanted areas.

Save Money by Improving the Ducts in Your Home

By having a professional HVAC company insulate and seal the ducts in your home, you can save a substantial amount of money and energy. The cost of having the work performed should be recouped within a few years. A local AC Southeast® dealer can assess your ducts and make improvements that will help you save money.