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building science... cleaning ductwork


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That's interesting. Very interesting.

I knew about the dust mite & fungal stuff, and always kind of had the feeling that the dirty ducts didn't necessarily mean poor IAQ.

But, if one is serious about air quality, I still think it's better to have clean ducts & an air filtration system tailored to the environment. The HEPA bypass types on new equipment are, in my view, the best thing going for forced air systems.

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Thanks Mike

Yes, it's taken me a while to stumble onto this site. I'm happy to have found it. There are experienced inspectors who do their homework posting here.

That Caoimhín Connell sure gets around and his writing is always pretty interesting.

Sidearm HEPA filters are a really good idea, what's not to like?


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Cleaner air will always get my vote, it's just that the experts say that dirty ducts aren't the bogeyman that we all thought they were.

I still recommend they clean them when I shine my light down into them and see mounds of matted up dog hair, dogfood, and sticky substances that look like they're growing whiskers.

OT - OF!!!


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  • 1 month later...

I have read with interest about the pros and cons of duct cleaning. The standard ASRHE and EPA position is that duct cleaning is not necessary. That the duct system is itself is a filtering system will reduce the amount of air borne particulants in the air. This is correct within a very narrow view. It presupposes that the system is a lifetime system that requires no maintenance, ever.

When a home inspector sees a duct system it is usually poorly designed with loose connections, missing filters, water stains, and all mannor of nasty creepy crawlys (real or imagined) inside the ducts and air handler. At this point any reasonable person intutitively knows the duct system needs something.

The usual response is that the duct needs to be cleaned but the real issue is that the duct system was never designed to be cleaned or to maintain any specific level of air quality, only to transport air from one area to another. Cleaning an air duct is an inexact science to say the least. "Cleaning something that was never designed to be cleaned" is difficult at best.

The real problem lies with the lack of understanding of air quality issues and the need to keep all the transport systems clean. Everyone knows that even a sewer pipe needs to have a cleanout when it clogs up, and everyone understands the importance of chlorine in our domestic water pipes. But there is no provisions to maintain the duct system in our homes. No way to clean the air, no cleanouts in the ductwork, no access to the ductwork, particularly when it is enclosed between floors, and no way to even determine if the ducts are dirty. The duct system is presumed to last the life of the home which simply is not true.

I suspect the rise in the rate of childhood asthema is directly related to the lack of understanding of residential indoor air quality. Every house wife has been taught that clean is good and dirt is bad, but when engineers start stating dirt is good then there is a condumrum that needs to be resolved in the best interests of the children that occupy the homes.

Another important issue is the politics. Imagine the EPA coming out and stating there are inherant design flaws in the duct systems of our homes and it is the cause of childhood respritory problems. Imagine what would happen if they actually addressed the issue.

This is my first post on this forum. Be gentle.

Brad Deal

20/20 Home Inspections


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