Regularly vacuuming your air filters, which can extend their life, or changing your filters at least four to six times a year can help your heating system work more efficiently.
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Q: I recently moved from a home with wall-mounted heaters into one that has central heat and air and a duct system. How can I ensure my ducts are working efficiently?
A: Homes with central forced-air heating and cooling systems—furnaces, central air conditioners and heat pumps—use air ducts to deliver heated or cooled air through the home. Ducts are often concealed in walls or in areas of your home you don’t go to often, like a crawlspace, so many people don’t think about them as a way to save energy.
You may have seen ads with offers for air-duct cleaning, saying it will improve your home’s air quality and efficiency. But duct cleaning may not always be necessary for air quality, and there is no indication that just cleaning your air ducts will improve your system’s efficiency.
Duct cleaning may be necessary if:
- There is visible mold in your duct system or there was a recent flood that caused mold or mildew in your home.
- There is something in the ductwork impeding airflow, like debris or an infestation. Major renovations or new construction can put construction debris into the duct system, so after construction is an ideal time to consider duct cleaning.
- Your heating registers are releasing dust into the air.
- Home residents have allergies or asthma problems that have not been alleviated by other changes.
You can help your heating and cooling system work more efficiently by regularly changing your air filters. How often you change them depends on how much your system runs, whether you have pets and whether you periodically vacuum your air filters. For the average home, air filters should be changed four to six times a year.
While cleaning ducts may not do much for your system’s efficiency, sealing them is important for saving energy and lowering utility costs, particularly if your ducts are in unconditioned spaces, like a crawlspace or an uninsulated attic. In a typical home, 20 to 30 percent of heated or cooled air escapes through unsealed gaps and holes in the duct system, which can cost you money and make your home less comfortable. You wouldn’t put up with a leaking water pipe, so why put up with a leaking air duct?
The best way to assess the overall condition of your home’s ductwork is to have it tested by a professional home-energy auditor, who can conduct a duct-leakage test. If you can easily access your ducts, you might get by with doing your own visual inspection, which can identify larger holes and disconnections. Places where ducts meet or where they connect to a heating register are common places to find leaks. A professional trained in duct work can help identify and fix any gaps and leaks you may not be able to see.
Once gaps and leaks have been identified, you can work to seal your ducts. Small duct leaks can be sealed with mastic, a type of caulk. Larger duct leaks and disconnections may require additional lengths of duct, mechanical fasteners or special heat-resistant tape. Do not use duct tape—ironically, it is not designed to adhere well to ducts.
If you have ducts in unconditioned areas, like an attic or crawlspace, your ducts could be wasting energy by heating or cooling the surrounding air, even if there are no leaks in the ductwork. Adding insulation around the ducts in these areas can help reduce energy loss and increase the efficiency and comfort of your home.
Send questions to Energy Q&A, South Carolina Living, 808 Knox Abbott Drive, Cayce, SC 29033, email firstname.lastname@example.org or fax (803) 739-3041.