uninsulated SS flex liner - unsafe?

[bostock]

ss flex liner installed, solid. Had to remove insulation blanket in order to get it through the chimney. approx 35' length. top is connected, stove is in place waiting for me to connect and start first burn. Need some input here: draw (at 35') will be good, maybe too good (i will install damper if needed). But a 'guy who knows a guy' that does chimney liner installs for a living is telling me DO NOT BURN UNDER ANY CIRCUMSTANCES without insulating, period. I understand where he is coming from - the temp differentials will lead to faster creosote buildup.
Question to you experts: is an uninsulated flex liner a true hazard, or does it simply mean i need to sweep more frequently? I have no problem with frequent sweeping but i just don't have the funds to insulate (pour) a 35' flue. This guy has me a little scared now, but i know the knowledge/advice i find here is much more valuable than anything else i see/hear elsewhere.. Let me know what you guys think.

 

[CarbonNeutral]

It's true that the cooler chimney will create creosote faster, but the actual reason for the insulation is so that in the event of a chimney fire the heat will not be transmitted though the liner, masonry, and to any combustibles. Lots (maybe most?) of stove shop installed liners are uninsulated - not one of the four shops I spoke to had any interest in putting an insulated liner down (caveat: I do have a small flue, but I don't believe they were recommending insulation to anyone).

So, your options, you don't want to pull it I guess, so I would use it now, inspect and sweep regularly, and insulate as soon as the funds are available.

 

[BrotherBart]

The hazard, if I remember right, is that you have just a brick chimney with no tile liner. Uninsulated in that case is a major no-no due to the heat transfer to combustibles around the chimney.

 

[Stump_Branch]

The hazard, if I remember right, is that you have just a brick chimney with no tile liner. Uninsulated in that case is a major no-no due to the heat transfer to combustibles around the chimney.

So would it be alright with an SSliner in a brick chimney with full flue tiles? I also assumed so becuase normally thats where the flue gases went. Im thinking that insulating would only improve draft/prevents premature cooling of the flue causes build ups. But would I be quasi insulated already?

 

[CarbonNeutral]

The hazard, if I remember right, is that you have just a brick chimney with no tile liner. Uninsulated in that case is a major no-no due to the heat transfer to combustibles around the chimney.

So would it be alright with an SSliner in a brick chimney with full flue tiles? I also assumed so becuase normally thats where the flue gases went. Im thinking that insulating would only improve draft/prevents premature cooling of the flue causes build ups. But would I be quasi insulated already?

Flues with clay liners are supposed to built with an air gap between the tiles and masonry - this would help prevent the spread of a fire through to wood. Most however are not built with the air gap. So while the clay tiles are better than nothing, you mostly can't rely on them to provide the safety net you need.

Now, of course, perhaps the answer is to not have chimney fires.....

To the OP, if you have no tiles, then I wouldn't wait to insulate - in fact I would even think about rigid insulated pipe so that I could be sure that the pipe wasn't touching brick anywhere

 

[Shari]

I continue to be amazed that people think the 'only' reason to insulate the liner is to 'keep the liner warm to avoid creosote buildup'.

Yes, while that may be a side benefit, in my opinion installing an insulated liner 'insulates' your home from heat generated in the flue by greatly reducing the possibility of fire damage to your person & property.

My liner is insulated.

 

[Stump_Branch]

Excuse the direct wording, only, I can certainly see the second set of protection insulating adds. a high-alloy steel such as the 316 stainless steel is annealed at 1200 C, the operating temp of Kaowool, a standard in most high temp applications, is 1260 C...If we examine the melting point, hard to due with differences in density thickness etc. but for comparison, The same high alloy stainless steel melting point is 1432 C while Kaowool is 1760 C (again varies due to density etc. but th about 1/2" versus the .006" of stainless) Terra Cotta for example is fired in the 1250 C range, meaning a comparable temperature threshold. And to get off the temperature for a second we could go into the durability of said products. While again I'm sure in this case more would be better, I'm not doing some sort of disservice. My technical rant above is only to state that the insulation isnt a catch all for a fire, just another layer, and would most likely give you a few more minutes before all hell breaks loose (or till you realize th a problem anyways).

What I was attempting to reach was how much better does insulating help with draft, and build up? Better draft and higher internal temps throughout the system (flue) would be better. And I do understand that such a thin walled stainless will dissipate heat at an incredible rapid pace to that of insulation (airspace), but wouldn't the terra cotta and air space between that and stainless flue , minimal as it may be, have insulating properties?
sorry for the confusion

 

[CarbonNeutral]

Stump, the insulation isn't there for when the steel melts, so operating temps are not key - it's transmission of heat through an intact pipe, then through masonry to wood combustibles. You are right of course that it's just another layer of protection, but I guess that's what it's all about.

For your second point, if that was the case, then why do we have insulation in our walls instead of just an air gap? The insulation material itself does little to insulate, but the pockets of air that it traps are the key - air is a great insulator, as long as you don't let it move.

Don't know if that made it clearer or not....

 

[EJL923]

My flexible liner is UNinsulated, about 23'. It is an interior chimney with clay tile liner in good shape

I sleep well at night.

 

[Shari]

".... wouldn't the terra cotta and air space between that and stainless flue , minimal as it may be, have insulating properties?
sorry for the confusion

My non-scientific/mechanical impression is that it would, somewhat - however - unless a homeowner has a pro send a camera down a clay tile lined chimney there is no way to 'certify' the existing chimney meets current NFSC (National Fire Safety Codes).

If a person installed an insulated SS liner minor problems with a non-conforming clay tile lined chimney can be alleviated. (Info this last statment provided from the gurus on this list and also from our local code enforcement authority.)

Shari

 

[Shari]

My flexible liner is UNinsulated, about 23'. It is an interior chimney with clay tile liner in good shape

I sleep well at night.

And that is fine for you.

Fact is I had a slight disagreement with my stove shop when I insisted on an insulated liner. Their main issue was I didn't need it because our chimney is an interior chimney. I thought about that for just a nano second and then proceeded to insist on the insulation - yes, it cost more $$ - but - we have no direct access exiting our home if/when a fire would start in the stove room - we would have to exit past the woodstove/chimney to get out (other than using a window - old people don't go through windows too well! )

Having lost a relative in a house fire (not woodstove related), while I can not choose how/when I die dying in a fire would not be a first option for me & mine.

Shari

 

[CarbonNeutral]

My flexible liner is UNinsulated, about 23'. It is an interior chimney with clay tile liner in good shape

I sleep well at night.

And many people drive without a seatbelt without any concern. Just not my cup of tea. Each to their own.

 

[branchburner]

What I was attempting to reach was how much better does insulating help with draft, and build up? Better draft and higher internal temps throughout the system (flue) would be better.

Insulating should help draft and reduce buildup. At 35' though, I don't think the OP will want any more draft!

Can insulating a liner, in a chimney with no flue tiles, be safely done by using loose perlite/vermiculite only? I'm guessing not, but thought it worth considering.

 

[Stump_Branch]

Stump, the insulation isn't there for when the steel melts, so operating temps are not key - it's transmission of heat through an intact pipe, then through masonry to wood combustibles. You are right of course that it's just another layer of protection, but I guess that's what it's all about.

For your second point, if that was the case, then why do we have insulation in our walls instead of just an air gap? The insulation material itself does little to insulate, but the pockets of air that it traps are the key - air is a great insulator, as long as you don't let it move.

Don't know if that made it clearer or not....

Correct, thats what I was thinking, I think I read it someplace here...my guess was the amount of 'free moving' air, versus the trapped. Sorry to the OP for the side track, just figured wise minds would be reading and be able to clearify. (mine is only 13' non-insulated, and while the draft is okay, it could be better. I was trying to figure out 'my' most cost effective method for improving this.)

However safety? probably go the easy way out and say it depends on the setup. But having a metalergist as a dad...and personally work for a company that designs/manufactors process plant dryers and kilns....I'll go with no, well not really. your more likely to have an issue with the pipe touching a part of the chimney, corrosion poking a hole, or you with a brush, then with all out failure. But why wouldnt you want a more efficent easier to operate and have another safety blanket (haha no pun intended there accidental) then not. if anything it would prevent drastic changes in the surface temps of the stainless, less fatigue.
I guess after this year I'll either pull it out and wrap (a pain I'm sure) or do a pour of sorts. (can that be removed?)

 

[Shari]

I guess after this year I'll either pull it out and wrap (a pain I'm sure) or do a pour of sorts. (can that be removed?)

Wrap: I believe this is the better of the two choices. I never investigated the 'pour' types available but know there is a granular type and a slurry type (gurus feel free to insert the proper names here).

Regarding the 'pour' types: In my opinion ( ) unless you use stand-offs attached directly to your liner which should perfectly center the liner inside the chimney the pour types are ineffective. Also the liner might look centered with or without stand-offs but once you start to pour can you guarantee there are no air pockets where the pour didn't get in place correctly?

Just my opinion - to each his own.

Regarding a "slurry" pour insulation: I don't think this can be removed at a later date but I'm not sure.

Shari

 

[Stump_Branch]

Dang, I was hoping a pour for ease, I am going to be cursing up a storm to haul that thing out. Not to mention the cost. I have also read about folks insulating the last 'x' feet...does this aid in anyway? I was figuring it was for interior chimneys, where the last few feet are exposed, but I think even the top portion of mine exterior one could benifit., any thoughts on that? I have some Kaowool from stuffing the flue where the liner goes through, stuff from work that, fell off the back of a truck, maybe the last few feet would at least be a bandaid till summer months?

 

[Shari]

Dang, I was hoping a pour for ease, I am going to be cursing up a storm to haul that thing out. Not to mention the cost. I have also read about folks insulating the last 'x' feet...does this aid in anyway?

To paraphrase CarbonNeutral: Driving a car while holding onto an unbuckled seat belt is not the same as a buckled seat belt.

 

[Stump_Branch]

Yes this can be true but does it aid? I might as well do the best I can till I am able to insulate. i would have done it to start with but like I mentioned, very difficult financially.

 

[Shari]

Yes this can be true but does it aid? I might as well do the best I can till I am able to insulate. i would have done it to start with but like I mentioned, very difficult financially.

Well........ there's a couple ways to look at your question... I choose only to answer the financial one: It cost us $900 additional to insulate our liner (pro installed). I think we have a $2,500 deductible on our homeowners insurance. Financially it was better off for us to spend the $900 up front for the insulation.

Shari

 

[DanCorcoran]

OP,

Food for thought: if you do have a fire that causes property damage, is your insurance company going to balk at paying, especially after you've provided all this online documentation of your concerns? My understanding is that, in this day and age, insurance claims departments have been known to do internet searches for just such info.

 

[tfdchief]

OP,

Food for thought: if you do have a fire that causes property damage, is your insurance company going to balk at paying, especially after you've provided all this online documentation of your concerns? My understanding is that, in this day and age, insurance claims departments have been known to do internet searches for just such info.

That's it....I'm done posting :ahhh:

 

[bostock]

wow, what a ride LOL.... with regards to heat transfer from uninsulated ss liner: are normal flue temps likely to cause this problem, or are we particularly talking about chim-fire temps?

 

[Shari]

That's it....I'm done posting :ahhh:

Well, you asked a question. You got some answers (both pro and con).

You don't have to 'choose' which answer is 'right' just choose the 'right one' for you and yours.

If you continue to have any concerns check with your insurance company to see what they require. Insulating your liner may fall above and beyond what your ins. company requires.

As for me and mine I know I have done the best install possible. I also know our install passes and even supersedes both our local codes and the requirements of our insurance company.

To each his own (meant in a nice way).

Shari

 

[CarbonNeutral]

wow, what a ride LOL.... with regards to heat transfer from uninsulated ss liner: are normal flue temps likely to cause this problem, or are we particularly talking about chim-fire temps?

More than likely not, with the huge caveat concerning the state of your flue. I was talking to some friends at the weekend - they can see exposed framing up one of their chimneys...

 

[tfdchief]

That's it....I'm done posting :ahhh:

Well, you asked a question. You got some answers (both pro and con).

You don't have to 'choose' which answer is 'right' just choose the 'right one' for you and yours.

If you continue to have any concerns check with your insurance company to see what they require. Insulating your liner may fall above and beyond what your ins. company requires.

As for me and mine I know I have done the best install possible. I also know our install passes and even supersedes both our local codes and the requirements of our insurance company.

To each his own (meant in a nice way).

Shari

Shari, I think you have me confused with the poster, bostock. I was just saying if the insurance companies are monitoring what I say on hearth.com, I'm done posting lol. Steve