We are often asked our opinion on duct cleaning…

GLS Engineering is hesitant to recommend duct cleaning as a stand-alone solution to Indoor Air Quality. Why? Because ducts should not require routine cleaning - if your ducts are dirty, there is a problem that needs to be addressed.

If ducts are dirty due to a one-time occurrence, such as failure to provide adequate filtration during a renovation, then we believe duct cleaning can be effective in returning the duct system to a cleaner condition.

Ducts that are dirty for other reasons, however, need to be properly diagnosed. If ducts are dirty due to duct leaks or other building-related issues, having the ducts cleaned is like mopping the floor while its still raining.  Keep in mind that the contaminants deposited on the interior surface of the duct system are only a small portion of what has actually gone through the duct system – the lion’s share was deposited into your home.

We are lead to believe that dirt in our ducts contaminates our indoor air. In fact, it’s the air in or around our home that contaminates the ducts.  Air leaks, either building related or in the ducts themselves (particularly when located in a crawl space or attic), are notorious for contaminating our ducts and interior spaces. Back to our mopping analogy – would you rather mop the floor or stop the rain?

But I have been told that I should regularly clean my ducts…

The only sources we have found recommending periodic duct cleaning are those directly vested in the duct cleaning industry.  No authoritative industry organizations (such as the American Society of Heating Refrigeration and Air-Conditioning Engineers (ASHRAE) or the Air Conditioning Contractors of America (ACCA) indicate such routine maintenance.  In fact, the EPA actually cautions consumers that are considering having their ducts cleaned - Should You Have the Air Ducts In Your Home Cleaned?

What about damage to my ducts?

Although well built metal duct system can withstand a thorough duct cleaning, those that are prone to installation-related leaks may fair less well when cleaned, and damage may occur that can actually make air leakage worse.  Flexible ducts are far less resilient than metal, and although there are companies that say they can clean flex duct, the chances of tearing the inner liner or dislodging the duct at a connection point are significant. Unfortunately, this damage is something that often goes un-noticed by the duct cleaning company and certainly by the homeowner.

Final note: If your ducts look like the ones in the duct cleaning ads, you have serious issues!