[Residential HVAC] FAT Duct: To Clean or Not to Clean?

[LoneRanger]

The interwebs seem to be split on the matter of whether to clean flexible air tight ducts or replace them. I have a local HVAC contractor who says they clean them all the time with no damage done during the process. They say it depends on how you go about it and what equipment is used. Doing with the wrong equipment and/or technique will compromise the plastic lining.

 

[Donald]

Do they need to be cleaned? I am considering installing one of the filter units that is inline with the return air and the filters are several inches thick. Hoping that will eliminate the need for having the ducts cleaned.

 

[LazyDog]

Depends on how old they are, plastic becomes brittle with time and heat. My sister owns a Mobil home, and we replace the flexible ducts last year.

More labor than money since they where under the trailer, lots of dust and some broken places.

 

[StevieC]

I have never cleaned vertical runs because of air-flow and gravity and the two in the bedrooms upstairs do a straight drop from the floor and with a flashlight I can see they are clean, I do however clean the horizontal in all the houses I have been in if it's dirty. I just cut a big enough hole that I can stick my head in up from the bottom and then feed a long shop-vac hose down and suck up all the dust.

In this house, I have 2 holes cut big enough for me to stick my head in and look down the run, one at either end and I can get the 12 foot run clean no problem. I then cover the holes with the access panels meant for drywall that have a door. I just seal them with aluminum foil tape when I'm done.

I can see this won't work for those that just have duct lines coming off the furnace itself or flexible duct runs. But in my case where there is a main horizontal run so it's easy for me.

I found a couple of handfuls of dust bunnies in the shop-vac afterward. I don't see it really being necessary so long as you are using a quality furnace filter of at least Merv 8.
I just checked them in September (5 years later) and there was a fine layer of dust but not enough to warrant a cleaning.

I keep my circulation fan on 24/7 to keep the floors balanced in humidity and temperature too.

 

[gman2304]

Some good info on the EPA website. Indoor air quality faq's.

 

[maxdustington]

Originally Posted by LoneRanger
I have a local HVAC contractor who says they clean them all the time with no damage done during the process. They say it depends on how you go about it and what equipment is used. Doing with the wrong equipment and/or technique will compromise the plastic lining.
I'll bet they have repaired or replaced a lot of them due to damage from hamfisted owners.

 

[EA82]

I would only consider cleaning metal ducts, if flexible ducts need cleaning it's time to replace them and not waste money.

 

[SZR48207]

Assuming the flex duct is correctly installed (taut with solid bends), they are not likely to be as dirty as you imagine. I went down this road a few years ago, and was so concerned that I DIY replaced all the flex duct in my attic.

The old duct which I assumed was filthy was fine.


If you want to do something, you should mastic seal the ducts at each end. Attic dust can easily get sucked into the airstream due to pressure differences at pinhole penetrations and most installers do lazy work on proper air sealing of the flex.