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repairing asbestos heat duct

hazel8's picture

I am caretaking an old house with asbestos heating ducts. The house has settled and opened up a seam between sections of duct- any suggestions on the best way to seal the gap (@ 3/4" all the way around the duct. I have used duct tape as a temporary fix but would appreciate expert opinions-thanks, Hazel8

(post #113754, reply #1 of 22)

If you used the ordinary gray fabric based "duck" tape that is not very permanate.

But there is a aluminum foil based duct tape that has a peal off liner on the adhesive that has a UL approval for use on heating ducts. A different kind of duck work, but it seems to last.

It is available in the home horror stores. Sometimes by the other tapes, sometime in the section with heating and venting ducts.

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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
. William the Geezer, the sequel to Billy the Kid - Shoe

(post #113754, reply #2 of 22)

Is this in the ground or suspended? Suspended I'd think that fibered duct mastic would probably be the best choice. Below grade probably a filled epoxy.

You should make an effort to remove any fractured fragments before sealing. If access is available, sealing from the inside would be best.


Half of the harm that is done in this world is due to people who want to feel important. They don't mean to do harm but the harm does not interest them. --T.S. Eliot


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

(post #113754, reply #3 of 22)

Hi Dan,
The duct is about 2 inches above the ground and about a foot from the floor joists (which is why I am down there doing this and not my big boyfriend)My boyfriend suggested we use spray insulation to seal the gap-which I am not crazy about doing- I was thinking of using tape and then wrapping that section with foil backed insulation sheets- what do you think????Hazel8

(post #113754, reply #4 of 22)

hazel..... i'd be very leary of doing anything with an asbestos duct system,


i  wouldn't touch it... i can't think of a better way of blowing friable asbestos fibers around a house


i'd dump it  right back on the owner


Mike Smith Rhode Island : Design / Build / Repair / Restore

Mike Smith Rhode Island : Design / Build / Repair / Restore

              www.mfsmithbuilder.com

(post #113754, reply #5 of 22)

i would be willing to bet that the asbestos is a white insulation material wrapped around sheet metal ducts, that is what was commonly used for heat delivery fom many types of heating systems.


i would be more worried about bringing friable asbstos into the house with a gravity system as opposed to a forced air system, but with either system you should have a sheet metal duct that needs to be repaired and secured and supported and then insulation repair.


wearing of a HEPA respirator (purple filters) is required to work with that stuff, as well as other methods of making sure you don't bring asbestos fibers into the house.

(post #113754, reply #6 of 22)

I was assuming we were talking about Transite duct.


Half of the harm that is done in this world is due to people who want to feel important. They don't mean to do harm but the harm does not interest them. --T.S. Eliot


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

(post #113754, reply #13 of 22)

i have never seen a transite "duct". i have seen many transite "vents".


it could be a transite duct, i never heard of a drum trap before either, but they exist.


i have seen lots of transite covered (insulation) sheet metal ducts.


if it is a vent and it is leaking it needs professional attention ASAP. the products of combustion from natural gas can kill people. (aldeheide gas? spelling) without them ever knowing they were at risk.


i am hoping it is a duct that is leaking because thats what original post was about if memory serves, language is so important to communication.

(post #113754, reply #14 of 22)

now that i look at the picture and read rest of posts, ( i responded to dan before reading the rest) i see that "southbay" says "transite" is used as "duct" where i have only seen it as "vent".


the picture that mike reposts from southbay looks to me like metal duct with transite insulation. with the engineering controls i think that is fairly safe to work with, unless you are cutting or breaking it very little to become friable. the problem is getting anything to stick to it, and removing it to repair leaks in metal duct.


very probably a good case for a professional to do the job properly as southbay suggests 

(post #113754, reply #16 of 22)

My photo that was reposted is not a metal duct covered with transite, but an extremely friable (will release lots of fibers easily) asbestos corrugated paper insulation. Sorry, I listed the photos and descriptions by number but they did not stack in the same order.

Transite is hard, asbestos-cement - portland cement with asbestos. Transite, though a regulated asbestos material, is usually not friable when intact and undisturbed. Proper work practices are still required if you are planning to do anything that may disturb it.

Photo of transite pipe fed from downspout. (Photo may not be rotated vertically.)

Photo of corrugated transite panel in greenhouse.

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(post #113754, reply #18 of 22)

thanks for the correction.

(post #113754, reply #20 of 22)

Yeah, your shot of the Transite downspout shows basically the same stuff that's used for furnace ducts in our slab.


Half of the harm that is done in this world is due to people who want to feel important. They don't mean to do harm but the harm does not interest them. --T.S. Eliot


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

(post #113754, reply #21 of 22)

I ended up crawling under the house, jacked up the joist (that was resting on the duct and caused it to open),carefully dug out dirt under the duct and covered the split with foil tape and then wrapped a piece of foil covered bubblewrap(don't know the technical term for it)around the whole shebang. The material of the duct doesn't really look like your picture-it looks more like masonite (down to the woven tecture on the surface)I am not messing with this @$#$ anymore...awfully dusty,dirty work plus-I am fond of spiders-but not in such close proximity.Thanks for all your input. Hazel8

(post #113754, reply #15 of 22)

I'm currently sitting about two feet from a heat register cut into the transite duct below the slab.


Half of the harm that is done in this world is due to people who want to feel important. They don't mean to do harm but the harm does not interest them. --T.S. Eliot


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

(post #113754, reply #17 of 22)

wow, i had no idea it was ever used that way, tell me please what keeps it from decaying over time and dusting the inhabited space with asbestos fibers?


is it possible for that to happen?


i thought that was the reason it was only used as vent, i know its not harmful in its solid state, but if it started to crumble? yikes 

(post #113754, reply #19 of 22)

Transite is an asbestos/cement composite, and the form of asbestos used is the long fiber type that doesn't become airborne very readily. Not something that I'd recommend folks install in a new house, but not all that scary to have in an older home.

If for some reason I needed to cut/drill into it I'd just wet it down good before starting, and then wet-wipe up well afterwards.

BTW, odds are that several folks reading this are drinking water out of Transite water mains.


Half of the harm that is done in this world is due to people who want to feel important. They don't mean to do harm but the harm does not interest them. --T.S. Eliot


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

(post #113754, reply #7 of 22)

If you have to fix this yourself, I would recommend getting a short coil of aluminum flashing about 8" wide. The stuff is very springy and will try to uncoil when not tied.

Before you go under the house, cut a piece long enough to more than wrap around the duct.

Wrap the edges of the break with foil-type duct tape to minimize the amount of asbestos fragments getting into the air.

Coil your piece of flashing and place it inside one section of the broken duct. It will expand to fit snugly against the inner walls of the duct. Now re-align the duct sections and slide your aluminum coil halfway into the other section, thereby bridging the gap between them. Wrap the repair securely with foil-type duct tape.

As one of the other posters said, be sure to wear a suitable mask to prevent breathing in any asbestos particles.

I'd probably also temporarily place a HEPA filter inside any register downstream from the break to capture stray particles that may have gotten into the duct.

BruceT
BruceT

(post #113754, reply #8 of 22)

There are several different combinations of asbestos ductwork and asbestos insulated ductwork. If you are dealing with anything except transite duct (comes in square sizes too) I would not recommend you do the repair. Friable asbestos, ACM that can be pulverized by hand pressure, will release many, many fibers when you try to work with it. Proper personal protective equipment and work practices are a must. Depending on how friable and dirty the duct is, you may not get any tape to stick. Besides the crawlspace may already be contaminated and you will disturb fibers that are laying in the dirt. You may also contaminate the house and heating system.

Photo 1 - Aircell corrugated asbestos paper insulation on metal ductwork.

Photo 2 - Transite asbestos-cement round duct.

Photo 3 - metal duct with asbestos cast-in-place "mud" insulation.

Photo 4 - Aircell corrugated asbestos paper insulation with asbestos 'mud' coating on metal duct.

Bart Gallagher
Enviroscience Consulants, Inc.
(631) 580-3191

(post #113754, reply #9 of 22)

Thanks for the pictures. THe duct I am talking about looks most like the first of your pictures- but more rigid- the duct is made out of what looks like asbestos board-perhaps it is something else-it is not covering other metal duct-the duct is constructed out of the panels themselves-the panels are about the thickness of masonite...what other material could they be?cement board? fiberglass?thanks for your input. Hazel8

(post #113754, reply #10 of 22)

if it looks like this type of ductwork



and it's old, then it's probably exactly what you called it


asbestos board.... used to be very readily available, you could buy it in 4x8 sheets


not something i'd want to be messing with, or want to disturb.. i can't think of a better way of distributing friable fibers thruout the entire house


Mike Smith Rhode Island : Design / Build / Repair / Restore

Mike Smith Rhode Island : Design / Build / Repair / Restore

              www.mfsmithbuilder.com

(post #113754, reply #11 of 22)

I was wondering -- can you make that image file a little larger? It's not loading near slow enough.


Half of the harm that is done in this world is due to people who want to feel important. They don't mean to do harm but the harm does not interest them. --T.S. Eliot


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

(post #113754, reply #12 of 22)

Sounds like you have a transite asbestos-cement duct. Same material as the shingles we discussed last month, and the photo of the round duct from my earlier post. Transite comes in several flavors. Flat sheet varying from say 1/8" on up to 3/4" thickness, corrugated - like those plastic patio panels, round pipe of various diameters...

The personal protective equipment (respirator, clothing), engineering controls (containment, wet methods) and work practice issues remain. As well as legal issues (you may be prohibited from doing this work). And liability issues (you may do more harm by disturbing the ACM and crawlspace). I would advise the owner and have the work done properly.

Without seeing the job and making no warranty.
In the interest of being practical, you may be able to encapsulate the sections you have to work on with spray paint. Then re-connect with flashing and tape.

how to identify asbestos heat ducts (post #113754, reply #22 of 22)

Greetings,

I am looking at a house built in 1972 with concrete slab flooring. The heat ducts run under the slab - no crall space, so I can not see the outside of the suspected asbestos ducts. But I can look down a heat vent and see the inside of what appears to be a transite asbestos-cement round duct. But it has spiral marking running down the pipe - not square weave markings like I see in a lot of pictures of asbestos material. Is there anyway to confirm that this is or is not asbestos from these markings?

Thanks,

-Nate.

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