Insulating steel liners in internal masonry chimneys when relining

[oconnor]

I've read many threads this year on insulating liners, and I've felt one piece of decision making information is under represented, so here it is.

Many think of insulation as an aide in improving draft and preventing creosote, which is true. Some suggest it is therefore not needed when dealing with an internal chimney.

That just isn't true in most cases.

Many liners require insulation if you are unable to determine an air gap between the outside of the masonry structure and combustibles. The insulation serves to break the radiant path that can over heat the brick.

The required air gap is usually one or two inches - not normally present with an internal flue. The specific details are listed in the instructions that come with the liner. Read them. If the liner doesn't come with instructions, don't use it and buy one that does.

Whether or not the flue has clay liners or not isn't a factor that I have read in manufacturer's instructions. I have seen it mentioned by some as a reason to not need to insulate the new liner, but I disagree. In the end, the manufacturer's instructions apply.

For those who want some more details, here's a link to a document that covers best practice for relining flues. It essentially says this:

1. Reline for valid technical reasons.
2. Provide accurate, credible information to the homeowner.
3. Inspect the chimney carefully and prepare it for relining.
4. Select the appropriate liner for the task.
5. Insulate the liner except in special circumstances.
6. Follow the liner manufacturer’s installation instructions and use components correctly

Here is the link:
http://woodheat.org/attachments/article/bplinerretailers.pdf

 

[bholler]

I would like to add if your chimney is clay lined and there is not enough room for insulation break out the old clay. it is serving no purpose anymore and usually you are putting in a liner because the clay failed in some way. many times even if there is enough room for insulation but the clay is in really bad shape or really dirty we will break it out anyway to make sure the chimney is clean. and lots of times we find that the outside of the clay is almost as dirty as the inside.

 

[begreen]

An alternative to breaking out the clay might be to go with pre-insulated M&G DuraLiner.

 

[BrotherBart]

usually you are putting in a liner because the clay failed in some way.

No you are not. Usually you are putting it in for draft.

Good grief some of your liner posts are just plain wrong.

 

[oconnor]

The key is that if a chimney can't be confirmed to maintain the needed clearances around the outside of the brick, then whatever liner is used needs to provide for the reduced / zero clearance situation. That could be a prefab insulated liner or a wrapped rigid or flex unit.

As I see it, internal masonry chimneys are more likely to need the insulated liner due to the clearance issues.

 

[_CY_]

No you are not. Usually you are putting it in for draft.

that's why I installed my 8in stainless liner purely for the increased draft .. Buck 91 would not draft properly unless there was a full liner. yes I did try Buck 91 without a liner. that was a no go ..

volume of exhaust going up the chimney drastically dropped with new insert. air has to heat to rise. without a liner exhaust gases from Buck 91 would draft when fire was roaring. but once air was throttled down with cat engaged. tiny amount of exhaust could no longer keep enormous chimney heated, stalling draft.

 

[bholler]

well most of the liners we put in (and we do 60 or so a year) are because the existing liners are either damaged of deteriorated. lots of times we are replacing because of fire damage. not yes we try to talk people into lining for draft but most of the time if their setup is working they see no need to improve it. now of course we will put a liner in a perfectly good 12 by 12for a wood stove for draft reasons but honestly most of what we do is in 7 by 7 flues and they worked ok they were just damaged. so no my post was not wrong just a different prospective. now in my house I put one in for draft so yes that is a very good reason but again that is not what most of our work is. we also do quite a few for modern high efficiency furnaces and those are mainly for draft but the clay has usually deteriorated to the point that stuff is falling down and blocking the chimney.so it is also because of bad liners. and by the way is a clay liner is sound and they have draft and no clearance issues we would never tell them to put a liner in just to improve draft. and yes every liner we put in is insulated. we usually use pour in but also wrap in some situations. we havnt used the preinsulated stuff yet we can actually do it cheaper for the customer with pour in. bt it would be a good solution in some situations I a sure

 

[Christopix]

Is there a way of confirming that my SS liner is/isn't insulated? Center of the house chimney, approx 25' to peak, 4' above peak, rectangular flex liner by Home Saver. Former home owners had it put in after having a small chimney fire. I've tried looking closely in the area of the basement clean out, in and around the thimble, and the at the top of the chimney. What should I be looking for?

 

[bholler]

and I am sorry brother bart but how many liners have you done and how much training have you had on doing them buy qualified instructors? most of my info comes from csia recommendations as well as code and years of experience doing this. I have been doing it for 7 years and my father has been doing it 36.

 

[bholler]

you would have to pull the top plate to see if you can see insulation. I can usually tell by the sound and feel when i am brushing the liner but you don't have a reference to compare to. non insulated ones sound hollow while insulated sound solid. it could be pour in or wrap so it would either look like it is wrapped in foil or you will see really rough cement from the top or from the bottom if you pull the packing out there would be some powder come out.

 

[bholler]

and by the way oconnor I absolutely agree with your op and I try to stress that to customers but most either cant or wont understand the dangers involved so we sell few liners for clearance reasons. but for us we don't offer an uninsulated option so that isn't an option for them from us.

 

[fire_man]

we usually use pour in but also wrap in some situations. we havnt used the preinsulated stuff yet we can actually do it cheaper for the customer with pour in.

Why do you prefer the pour stuff? I went back and forth on that, but decided if I ever needed to "tweak" my setup the wrap is easier. I assume by pour you mean the stuff that sets up?

 

[bholler]

yeah it is a cement and vermiculite mix. we use it because lots of the chimneys we are working on have had coal burn through them at one point and any coal dust left will eat the covering on the wrap in a couple years while the pour in isolated the liner from the walls of the chimney and isn't affected by the coal residue. it also stabilizes any flaws in the inside of the chimney and keeps the liner more stable. I have absolutely no problem with wrap and we use it often. part of it is we are just used to doing the pour in and for us it is easier in many ways so in a situation where either one would work evenly well we will choose pour in. allot is just preference. also we almost never pour in on an insert install it would use tons of insulation and there is to much potential for leaks at the bottom.

 

[fire_man]

Bholler:

Have you ever had to "adjust" a liner that had poured insulation? I installed a bigger stove and it was easy because all I did was lift the whole liner a couple inches from the top to make room for the new stove. If it was poured I would have had to cut the lower liner and then could not have slid the liner up or down to get the final length "just right".

 

[BrotherBart]

and I am sorry brother bart but how many liners have you done and how much training have you had on doing them buy qualified instructors? most of my info comes from csia recommendations as well as code and years of experience doing this. I have been doing it for 7 years and my father has been doing it 36.

Makes no difference how many me or anybody else has put in. Now if you had originally said that most you install are for damaged chimneys instead of just saying that most are installed for that reason....

But to wade into a house and bust the tiles out of a perfectly good chimney and forever prevent it from being reverted to an open fireplace is just a disservice to the customer and added cost to them.

 

[Christopix]

you would have to pull the top plate to see if you can see insulation. I can usually tell by the sound and feel when i am brushing the liner but you don't have a reference to compare to. non insulated ones sound hollow while insulated sound solid. it could be pour in or wrap so it would either look like it is wrapped in foil or you will see really rough cement from the top or from the bottom if you pull the packing out there would be some powder come out.

You are right, I don't have any comparison so using sound would be a guess…

Is there any possibility of me messing things up if I pull the top plate (at the very top of my chimney, below the cap I assume?) and have a look? And, if I don't find any evidence of insulation, wrap or powdery stuff, is it possible to insulate after the bloody liner is in place? Keep in mind this is a rectangle flex liner by Home Savers.

 

[Rudyjr]

Brent I would say you are absolutely right about clearance on fireplaces built before the 1940's. I have never seen a fireplace that meets current code in a house built before 1930. But I believe you would be hard pressed to find an all masonry fireplace, at least in my area built after 1950 that had clearance issues, Many of these fireplaces need lined and insulated because they have been compromised through the years by lack of maintenance and over firing. But I have no problem going along with someone putting in just a liner when they have their fireplace inspected by a competent, certified chimney professional that has given them the green light to proceed. I have been in the construction field for close to forty years and my family has been in the homebuilding business in one form or another since the fifties so I have had lots of opportunity to see this firsthand.

 

[oconnor]

Makes no difference how many me or anybody else has put in. Now if you had originally said that most you install are for damaged chimneys instead of just saying that most are installed for that reason....

But to wade into a house and bust the tiles out of a perfectly good chimney and forever prevent it from being reverted to an open fireplace is just a disservice to the customer and added cost to them.

Bart

That's exactly what I understood when I read his post. It's not English class. (We vs you vs when one etc) It's his opinion based on his experience. He used the wrong word. He also missed a few capital letters.

The thread isn't about semantics.

If the insulation can't be installed with them in place, or the structure of them is in doubt, they need to come out.

 

[bholler]

well you need to make sure he liner isn't hanging from the top plate freely before you un hook it if it is that could be bad. I would try lifting the top plat up a bit and see if the liner is hanging. lots of times they are sitting on the bottom of the chimney and then it would not be a problem but it is hard to tell. an yes if there is room you could pour in insulation now but I would guess that they put in a rectangle liner because they didn't have room for a round which means there might not be room for insulation either.

 

[fire_man]

Bart

That's exactly what I understood when I read his post. It's not English class. (We vs you vs when one etc) It's his opinion based on his experience. He used the wrong word. He also missed a few capital letters.

The thread isn't about semantics.

If the insulation can't be installed with them in place, or the structure of them is in doubt, they need to come out.

"It depends on what the meaning of the word 'is' is"

 

[bholler]

Thankyou oconnor and no we would not break out liners in a fire place usually because there would be room for insulation inside the clay. Now if the liners were cracked and covered with creosote glaze we probably would because we would not feel comfortable that we could get those liners clean and that there would not be creosote left outside those liners. If you read my original post it says "many times even if there is enough room for insulation but the clay is in really bad shape or really dirty we will break it out anyway to make sure the chimney is clean" I never said we break out perfectly good liners when there is room for insulation. I agree that that would be a disservice to our customers. By the way yes I know I don't capitalize I will try to work n that that lol.

 

[Christopix]

if there is room you could pour in insulation now but I would guess that they put in a rectangle liner because they didn't have room for a round which means there might not be room for insulation either.

Bugger!

Well, what might my options be then if I don't have insulation and, in fact, the rectangle liner doesn't allow for room to pour insulation?

 

[oconnor]

Brent I would say you are absolutely right about clearance on fireplaces built before the 1940's. I have never seen a fireplace that meets current code in a house built before 1930. But I believe you would be hard pressed to find an all masonry fireplace, at least in my area built after 1950 that had clearance issues, Many of these fireplaces need lined and insulated because they have been compromised through the years by lack of maintenance and over firing. But I have no problem going along with someone putting in just a liner when they have their fireplace inspected by a competent, certified chimney professional that has given them the green light to proceed.

In not sure how one would confirm that an internal masonry chimney had a two inch air gap the full length of the structure. I think that is what Gulland is saying in his article for the CSIA. Especially in a fireplace.

Fireplace flue gas temps are almost half of what an EPA stove produces, so the clearances to combustibles outside the masonry would be different.

Again, it's all about the instructions the manufacturer prescribes.

As for a competent and certified installer saying it is OK to install a liner uninsulated, sure, of he is certain that the clearances have been met. He will be doing so contrary to the guidelines of the CSIA, which is likely the group that trained him.

 

[fire_man]

well you need to make sure he liner isn't hanging from the top plate freely before you un hook it if it is that could be bad. I would try lifting the top plat up a bit and see if the liner is hanging. lots of times they are sitting on the bottom of the chimney and then it would not be a problem but it is hard to tell. an yes if there is room you could pour in insulation now but I would guess that they put in a rectangle liner because they didn't have room for a round which means there might not be room for insulation either.

What I'm saying is if there is already solid 'pour in insulation' holding the flue in place, you could not move the liner up and down and make vertical adjustments.

 

[Rudyjr]

In not sure how one would confirm that an internal masonry chimney had a two inch air gap the full length of the structure. I think that is what Gulland is saying in his article for the CSIA. Especially in a fireplace.

Fireplace flue gas temps are almost half of what an EPA stove produces, so the clearances to combustibles outside the masonry would be different.

Again, it's all about the instructions the manufacturer prescribes.

As for a competent and certified installer saying it is OK to install a liner uninsulated, sure, of he is certain that the clearances have been met. He will be doing so contrary to the guidelines of the CSIA, which is likely the group that trained him.

Not wanting to get into a pissing match about this just stating what is common approved practice in my area per building code, I don't like it when someone on here advocates busting the liner out of a chimney before it has been determined that it needs to be. ADIOS fellas have fun.