Thread: Mold in Duct System

I know mold in the HVAC ducting has been discussed several times in the past, but I can't over emphasize the importance of spot checking the air registers during your inspection. Several months ago I inspected a house and didn't do anything other than look at the exterior condition of the air registers and their immediate surroundings which there were no deficiencies that could be observed to make note of. Shortly after the buyer moved into his new home, he began to clean up the house and when he was on his step ladder, noticed a dark spot inside one of the air registers. He removed the register and observed a black powdery substance on the interior of the flex ducting. He contacted an HVAC Company to further inspect the ducting where they found mold in the ducting and removed and reinstalled four ducts. They also told him that the air handler, coil system and plenum were probably contaminated and recommended a new system. This is when I received a phone call from him. which I immediately went to the house and started my own investigation. Mold was observed in just about every duct on the side of the house that was closest to the air conditioning system with the exception of those that had already been replaced. I recommended that he have the ducts cleaned in which he contacted a Duct Cleaning Company. When the Duct Cleaner arrived and began to check out the ducts he unloaded on the HVAC Technician for not changing out the vent boots (which were also contaminated) when they installed the new ducting. The Duct Cleaner said that there was too much mold in the ducts to clean and that a risk of contaminating the remainder of the ducts existed and refused to clean the system. The Duct Cleaner recommended all of the ducts and boots be removed and new ones installed. Now the new home owner is scared if he gets a new duct system that the old Air Conditioning system is going to contaminate everything. I questioned the Duct Cleaner and he said that mold in ducts is not uncommon. Stated that sometimes when the home owner closes off one vent that condensation is in the conditioned air and will accumulate around the register and flex ducting was more prevalent because it would allow condensation to pond in and between the flexed areas. The HVAC System was a 10 year old Janitrol. Being bombarded by all kinds of advice the home owner ended up on gutting and replacing the entire HVAC system. Lessons to learn: Check the interior of the air registers, you don't have to get on a ladder and unscrew the vent, just shine your flashlight in there and if you see anything peculiar, start looking. Don't depend on the buyers Home Warranty to address this issue, they've done their home work. Reemphasize on your disclaimer in your Home Inspection Order Agreement concerning mold in duct systems.

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Consider using the Enter/Return key once in awhile....

The only way to "clean" a flex duct is to replace it.

100% of homes have mold. It is a standard disclaimer in every SOP and most contracts that inspectors are responsible for and do not inspect for mold.

You're correct in disclosure concerning mold, however, sometimes you need to be more specific. It helps during litigation.

Originally Posted by Bruce Carpenter

I recommended that he have the ducts cleaned in which he contacted a Duct Cleaning Company.

#1 - Not all ducts can be cleaned.
#2 - Not all ducts should be cleaned, but may need to be replaced.

I report duct cleaning this way:
Should you have the air ducts in your home cleaned?
EPA note about ducts: "Knowledge about air duct cleaning is in its early stages, so a blanket recommendation cannot be offered as to whether you should have your air ducts in your home cleaned. The U.S. Environmental Protection Agency (EPA) urges you to read this document in it entirety as it provides important information on the subject." Should You Have the Air Ducts in Your Home Cleaned? | Indoor Air | US Environmental Protection Agency (copy and paste into your browser)

"Duct cleaning has never been shown to actually prevent health problems. Neither do studies conclusively demonstrate that particle (e.g., dust) levels in homes increase because of dirty air ducts. This is because much of the dirt in air ducts adheres to duct surfaces and does not necessarily enter the living space. It is important to keep in mind that dirty air ducts are only one of many possible sources of particles that are present in homes. Pollutants that enter the home both from outdoors and indoor activities such as cooking, cleaning, smoking, or just moving around can cause greater exposure to contaminants than dirty air ducts. Moreover, there is no evidence that a light amount of household dust or other particulate mater in air ducts poses any risk to your health."

If a duct, or ducts, are wet, moldy, or otherwise contaminated, the most prudent course of action is to replace the duct(s) (rather than cleaning) to ensure removal of the contaminants. However, if a duct is contaminated, the source of contamination too, must be addressed. Often the contamination may reach into other components of the system(s).

Also, be advised that there are some types of ducts that cannot be cleaned due to the type of duct material.

It good to report what you state during the inspection. After the inspection and the buyer's in the house is another story. You feel bad enough that you didn't catch the deficiency and to recommend a less intrusive remedy to solve an issue has merit. If a reputable company who has been cleaning ducts for over twenty years with a good record says they can or can't clean the ducts it won't be me who argues with them. If there's an alternative to save money, cleaning versus replacement, I'll go with the recommendation of the expert(s). I'll put your statement in my canned phrases and use when appropriate. Thanks.