How do you clean an air duct that is fiberglass lined?

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dmreed4311

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May 3, 2010
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David Reed
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#1
I ran into an air duct this morning that was fiberglass lined.
I walked away from the job because I could only imagine what would happen if i put my spinner up in the duct. Iam new to air duct cleaning and have had good results so far but did not feel I had the knowledge to do this job.
Any thoughts?
 

Kenny Wright

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Jan 29, 2009
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#2
I only clean ductboard/ fiberglass lined ductwork if it is in good shape and I can physically stick my head into the ductwork while I'm cleaning. Even then, it has to be cleaned VERY gently. I'll use soft brushes and or a little compressed air to get the loose particulate out. If you are unsure with this stuff, err on the side of caution. Getting too aggressive with the fiberglass lining will put fiberglass particles in the ductwork. By the way, around here the stuff is usually orange in color on the inside when it's new. Don't expect the original color to return; it's still going to look dirty.
 

Scott W

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#3
As Kenny says, they can sometimes be cleaned gently. More often the choice is to either apply a coating to the lining or to replace the ductwork.

The encapsulation or coating method has some support but others have concerns that the coating may flake off with time and put little bits of polymers into the air stream where they could be inhaled. The other side of the argument says that the coating will last 7 to 10 years. You gain several extra years of use before you need to repalce it.

In most cases, I would suggest replacement. You don't want fiberglass particles blowing into the breathable air space.
 

Kenny Wright

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#4
If the branch runs are fiberglass-insulated, that stuff is old and problematic and needs to be replaced. Mostly all I see on branch runs around here is metal or flexduct. When fiberglass ductboard is used it is for the trunklines. Personally, I don't think much of ductboard. Metal is a much better way to go.

Unless you really know about ductwork installation you shouldn't mess with replacing the trunkline.
 

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Oct 13, 2011
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Ron Hampe
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#5
Condition is important, but unless its damaged to the point where replacement is obviously required then I recommend Heat Seal's 28"
Octopus Predator Whip. Unlike the shorter 14" whips, it strikes on the side of the whip instead of the tip and does a great job in fiberglassand they sell a low pressure version of it that works great in flex duct. Google Heat Seal Equipment ltd. They are located in Ajax, Ontario Canada.
 

Kenny Wright

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#6
I'll check it out and probably get one to try out but it will have to be REALLY gentle before I use it in ductboard.

Condition is important, but unless its damaged to the point where replacement is obviously required then I recommend Heat Seal's 28"
Octopus Predator Whip. Unlike the shorter 14" whips, it strikes on the side of the whip instead of the tip and does a great job in fiberglassand they sell a low pressure version of it that works great in flex duct. Google Heat Seal Equipment ltd. They are located in Ajax, Ontario Canada.
 

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#7
I've been using these for several years without a single problem. Whenever possible I open the end the duct and look thru it with a MagLight to determine condition before beginning. As with any cleaning tool used it is best to not remain in any one spot very long. If deteriorated, I'll push my rods thru to the opposite end before turning on the air pressure and pull them out in one continuous motion. I then make as many passes as are needed following these with an air sweep to blow out anything heavy that may have been left behind.

They also work well in internally insulated metal duct, but regardless of what you use to clean those you have to be careful that the lining is not already loose. The grip nails the hvac guys use often come loose and a single piece of loose insulation in a main duct can effectively block or significantly reduce air flow thru that end of the system.
 

jaymark

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Feb 8, 2011
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#8
Its ashame companies even install fiberglass duct boards, after a few years they start to fall apart and fiberglass begins to enter the air.

At the hvac company I worked for we installed toughguard ductboard. It is the same thing, but with a thick liner that is black on the inside.
 

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#9
Here's a video that gives you a general idea of how effective these whips are at safely cleaning duct board. At 17" in length this robot is quite large and I'm not sure how long their whip tentacles are, but they may be using low pressure ones instead of what I would normally use. Either way these are the type of results that I generally see.

Copy and paste the following link to see the video.

http://www.lloydssystems.com/videos_animations/DVD1.wmv