The EPA and CMHC researchers used different methodologies. The CMHC study called on several duct-cleaning services. The companies were not made aware they were part of a study, and the researchers did not control for time spent or methods used. The EPA study prescribed and controlled methods used on a smaller number of homes. While the duct-cleaning industry argues both studies have flaws, no other research has challenged the findings. And although the equipment and methods used by duct-cleaning companies have changed since these studies were conducted, the air ducts in homes haven’t.

The Canada Mortgage and Housing Corporation (CMHC), a government agency, conducted a study in the 1990s to investigate two claims: Duct cleaning makes indoor air healthier; and it reduces energy costs by improving airflow. After testing 33 homes in Montreal before and after duct cleaning, the study found that there was no significant improvement in air quality and that duct cleaning alone did not improve airflow or energy efficiency. In some cases, measured particle levels actually increased immediately after a cleaning. In other cases, particle levels decreased immediately after cleaning but returned to previous levels within weeks.
I’m having my duct work cleaned this Saturday. Have a coupon for $49 through Amazon. Job normally $249. Had my basement remodeled about 18 months ago. The contractors were very thorough at blocking the vents, as far as I can tell. The offer is for HVAC and dryer vent cleaning. My house is 11 years old. I figured, $49 is not much. I appreciate your tips on not getting talked into any additional service, not to use solvents to clean, the certification information and before and after pictures. Very useful and I’ll be sure that all I spend is the $49 for the voucher.
The EPA and CMHC researchers used different methodologies. The CMHC study called on several duct-cleaning services. The companies were not made aware they were part of a study, and the researchers did not control for time spent or methods used. The EPA study prescribed and controlled methods used on a smaller number of homes. While the duct-cleaning industry argues both studies have flaws, no other research has challenged the findings. And although the equipment and methods used by duct-cleaning companies have changed since these studies were conducted, the air ducts in homes haven’t.
According to National Fire Protection Association in 2010, an estimated 16,800 reported U.S. non-confined or confined home structure fires involving clothes dryers or washing machines resulted in 51 civilian deaths, 380 civilian injuries and $236 million in direct property damage.  (http://www.nfpa.org/safety-information/for-consumers/causes/dryers-and-washing-machines)
Another sketchy claim made by most duct-cleaning operations and their trade association is that dirty ducts and equipment overburden heating and cooling equipment, which wastes energy. Again, it intuitively makes sense that a cleaner system will run smoother and last longer — after all, that’s why we and HVAC-equipment manufacturers and repair services recommend that you regularly change your filters. But the page “Benefits of HVAC Cleaning” on the National Air Duct Cleaners Association (NADCA) website stretches this benefit too far by stating: “According to the U.S. Department of Energy, 25 to 40 percent of the energy used for heating and cooling a home is wasted.”
You may consider having your air ducts cleaned simply because it seems logical that air ducts will get dirty over time and should be occasionally cleaned. Provided that the cleaning is done properly, no evidence suggests that such cleaning would be detrimental. EPA does not recommend that the air ducts be cleaned routinely, but only as needed. EPA does, however, recommend that if you have a fuel burning furnace, stove or fireplace, they be inspected for proper functioning and serviced before each heating season to protect against carbon monoxide poisoning.
×