I recently moved from a home with wall-mounted heaters to one with central heat and air, and a duct system. How can I ensure my ducts are working efficiently?—Carla
Many people do not immediately think of the air ducts that deliver heated or cooled air as energy-saving targets. You may have received offers for air-duct cleaning with claims that doing so will improve the air quality and efficiency of your home. Duct cleaning may not always be necessary for air quality, and there is no indication that just cleaning the air ducts will improve your system’s efficiency.
However, duct cleaning may be needed if:
• There is visible mold in the 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 an
infestation or debris from renovations or construction.
• Heating registers are releasing dust into the air.
• Residents have allergies or asthma problems that have not been alleviated by other changes.
Though duct cleaning may not do much for efficiency, duct sealing saves energy and lowers utility costs, particularly if the 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.
The best way to assess the condition of your home’s ductwork is to have it tested by a professional home energy auditor who can conduct a duct leakage performance test. If the ducts are easily accessed, you might get by with a visual inspection to spot larger holes and disconnections. A professional trained in ductwork can help you identify and fix the gaps and leaks you may not be able to see. Talk to your local electric co-op about an energy audit or how to find the right person for the job.
Once duct gaps and leaks have been identified, seal them. Small leaks can be sealed with mastic, a type of caulk, while larger 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.
For more information on duct sealing, consult the 2014 Energy Guide.
Don’t forget to change air filters
While duct cleaning may not always be necessary, regularly changing your air filters can help your heating and cooling system work more efficiently.
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.
Patrick Keegan for the August 2016 issue