Chimney Height

[DeadTreeBurner]

What does the included listing info say? What does the installation instructions say about it?

Well, again, the ebay listing itself does not say anything about insulation, let alone requiring it for zero clearance.
The install instructions do not mention insulation either. Instructions do state: The "Forever Vent Chimney Lining System from Chim Cap Corp. is intended for use as a relining system for clay lined masonry chimneys only. Tested and approved to UL1777 zero clearance standards for masonry chimney serving gas, oil or wood burning appliances."

Instructions also recommend that a qualified Professional installs the kit, that it's sized per equipment manufacturer's instruction and local building codes and to contact your local building department or fire officials about restrictions and installation inspection in your area.
Chimney the liner is to be installed in must be checked for safety and repaired if necessary before installation.

So nothing at all in the listing or instructions about requiring insulation wrap, just that it's tested and approved to zero clearance standards in masonry chimneys. To your average consumer, that means it can be placed in any clay lined chimney that's in good repair. If they know a purchaser will be informed after purchasing by their inspector/installer, IF they use one, that insulation is required, well that's pretty deceptive. Because it appears from their advertisement/listing and install instructions, by themselves, that you don't need one. And we both know a large number of people will be installing liners themselves.

 

[parryvt]

Unless you have the required clearances yes you need proper insulation on the liner

Pre-insulated liners contain .50" of insulation and insulation blankets are .25" and .50" thick. Why the difference?

Thank you for sharing your knowledge and experience.

 

[DeadTreeBurner]

Pre-insulated liners contain .50" of insulation and insulation blankets are .25" and .50" thick. Why the difference?

Thank you for sharing your knowledge and experience.

1/2" insulation allow zero clearance of exterior of masonry to combustibles, 1/4" insulation requires 1" clearance from exterior of masonry to combustibles to maintain UL Listing 1777.

 

[parryvt]

Is your SS liner single wall? Or double ply smooth wall? There are double ply smooth wall liners that are tested and approved to UL1777 zero clearance standards. I just bought one, 6" x 30' in a kit for just under $500.

I wanted smooth wall, but the company I purchased from recommended the corrugated as they've had instances of the smooth walled unraveling during cleaning when used burning wood. I considered going elsewhere, but I appreciate their honesty and they have very responsive customer service.

 

[parryvt]

1/2" insulation allow zero clearance of exterior of masonry to combustibles, 1/4" insulation requires 1" clearance from exterior of masonry to combustibles to maintain UL Listing 1777.

But why the difference in thickness between a wrap and poured insulation? I'm guessing the wrap provides better insulation?

 

[bholler]

I wanted smooth wall, but the company I purchased from recommended the corrugated as they've had instances of the smooth walled unraveling during cleaning when used burning wood. I considered going elsewhere, but I appreciate their honesty and they have very responsive customer service.

Yeah that smooth wall stuff is the least durable type of liner

 

[bholler]

But why the difference in thickness between a wrap and poured insulation? I'm guessing the wrap provides better insulation?

The wrap has a higher k value than pour in

 

[DeadTreeBurner]

But why the difference in thickness between a wrap and poured insulation? I'm guessing the wrap provides better insulation?

I expect the answer is the poured insulation transfers more heat, hence requirement for minimum 1 inch of it between SS liner and inside of the masonry flue.
My perspective is that the insulation requirements to meet the UL standard for installing a SS liner in a masonry chimney in good condition are overkill and ridiculous. In my scenario, I have an exterior chimney in good condition and will be installing a 6" liner double ply smooth wall liner. The chimney, from thimble to top is 27' and the flue measures 6.5" x 11". There are no turns or bends. There will be minimal "point" contact of the liner with the terracotta clay flue liner inside the chimney in random spots. The amount of heat transfer from the SS liner to the chimney will be minimal, and the amount of heat that will be seen on the exterior surfaces of the brick will be practically non-existent, at least on my chimney. I've used a Buck Model 81 wood burner last season with NO liner and there was no appreciable heat transfer to the exterior of the chimney that I could tell. That's with stove pipe temps approaching 700 deg F before the thimble when the stove was maxed out. So as far as I'm concerned, I'm light years ahead of the game by installing a SS liner, the only thing I can see an insulation wrap doing for me is preventing or reducing condensation of water near the top on really cold days. Especially since I'm now using a pellet stove and flue temps at the stove outlet when the stove is maxed out is almost 400 deg cooler than with the wood burner.
I think the UL insulation requirement would be like the state's DOT requiring people to wear a bubble wrap suit whenever they get into a car in addition to a seat belt and being equipped with air bags. But that's my .02, everybody needs to do their own research and determine what risk they are willing to take.

 

[DeadTreeBurner]

Yeah that smooth wall stuff is the least durable type of liner

I did notice small points of buckling of the inner bands from the liner being coiled on mine. I was going to send it back, but I'm going to pull a roughly 6" wooden plug through it to flatten them back out. That thin 316L SS does bend really easy. Hopefully with the right sized nylon brush, and turning it when it's pulled back up won't cause any problems. I don't expect it will, they have a life time warranty on the thing and require it to be swept annually to maintain the warranty, so...

 

[bholler]

I expect the answer is the poured insulation transfers more heat, hence requirement for minimum 1 inch of it between SS liner and inside of the masonry flue.
My perspective is that the insulation requirements to meet the UL standard for installing a SS liner in a masonry chimney in good condition are overkill and ridiculous. In my scenario, I have an exterior chimney in good condition and will be installing a 6" liner double ply smooth wall liner. The chimney, from thimble to top is 27' and the flue measures 6.5" x 11". There are no turns or bends. There will be minimal "point" contact of the liner with the terracotta clay flue liner inside the chimney in random spots. The amount of heat transfer from the SS liner to the chimney will be minimal, and the amount of heat that will be seen on the exterior surfaces of the brick will be practically non-existent. I've used a Buck Model 81 wood burner last season with NO liner and there was no appreciable heat transfer to the exterior of the chimney that I could tell. That's with stove pipe temps approaching 700 deg F before the thimble when the stove was maxed out. So as far as I'm concerned, I'm light years ahead of the game by installing a SS liner, the only thing I can see an insulation wrap doing for me is preventing or reducing condensation of water near the top on really cold days. Especially since I'm now using a pellet stove and flue temps at the stove outlet when the stove is maxed out is almost 400 deg cooler than with the wood burner.
I think the UL insulation requirement would be like the state's DOT requiring people to wear a bubble wrap suit whenever they get into a car in addition to a seat belt and being equipped with air bags. But that's my .02, everybody needs to do their own research and determine what risk they are willing to take.

There has been extensive testing done by many different people. They determined that you need the required clearances for a masonry chimney. If you don't have that you need insulation on your liner.

 

[bholler]

I did notice small points of buckling of the inner bands from the liner being coiled on mine. I was going to send it back, but I'm going to pull a roughly 6" wooden plug through it to flatten them back out. That thin 316L SS does bend really easy. Hopefully with the right sized nylon brush, and turning it when it's pulled back up won't cause any problems. I don't expect it will, they have a life time warranty on the thing and require it to be swept annually to maintain the warranty, so...

How long is their determined lifetime of the liner?

 

[DeadTreeBurner]

How long is their determined lifetime of the liner?

As long as original purchaser owns the home it's installed in, and it's been properly installed and swept each year. They do have a phrase "for the lifetime of the product" thrown in the part about "as long as original purchaser owns the home". Wouldn't be surprised if that affords them legal wiggle room to point to some other document that states the product lifetime is 10 or 15 years or whatever.
Oh well, I guess I'll see.

 

[DeadTreeBurner]

There has been extensive testing done by many different people. They determined that you need the required clearances for a masonry chimney. If you don't have that you need insulation on your liner.

I certainly understand that. Given what I've observed, I'd like to see the method of tests, etc. though, b/c something doesn't jive with what I've seen w/ my setup. The dimensions of the exterior of my brick chimney and exterior of the clay liner certainly allow for an interior air gap which would explain why there's no appreciable heat showing up at the exterior of the chimney, even down lower where the gasses would be much hotter. So it would seem that the UL standard is generalized to provide safety for the worst case scenario, but overkill for certain setups?

 

[stoveliker]

I certainly understand that. Given what I've observed, I'd like to see the method of tests, etc. though, b/c something doesn't jive with what I've seen w/ my setup. The dimensions of the exterior of my brick chimney and exterior of the clay liner certainly allow for an interior air gap which would explain why there's no appreciable heat showing up at the exterior of the chimney, even down lower where the gasses would be much hotter. So it would seem that the UL standard is generalized to provide safety for the worst case scenario, but overkill for certain setups?

Long term (years) slight warming of wood decreases their ignition temperature. That is what is the problem l. Hard to recognize now when burning..

 

[bholler]

I certainly understand that. Given what I've observed, I'd like to see the method of tests, etc. though, b/c something doesn't jive with what I've seen w/ my setup. The dimensions of the exterior of my brick chimney and exterior of the clay liner certainly allow for an interior air gap which would explain why there's no appreciable heat showing up at the exterior of the chimney, even down lower where the gasses would be much hotter. So it would seem that the UL standard is generalized to provide safety for the worst case scenario, but overkill for certain setups?

I can absolutely agree with it being overkill for certain setups. They should have a thickness of masonry that would negate the requirements. But the problem is that in a existing structure it is extremely difficult to determine how much masonry there is between the clay and the outside of the chimney

 

[DeadTreeBurner]

Long term (years) slight warming of wood decreases their ignition temperature. That is what is the problem l. Hard to recognize now when burning..

Yep, bholler did mention that.
What's "slight warming" though? I came across a very interesting read on the subject here:

https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.553.9372&rep=rep1&type=pdf

Seems that you can have trouble at long term exposure to temps as low as 77C or 170.6F, which I would consider more than slight warming, but nonetheless good info to know about.

 

[stoveliker]

Yep, bholler did mention that.
What's "slight warming" though? I came across a very interesting read on the subject here:

https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.553.9372&rep=rep1&type=pdf

Seems that you can have trouble at long term exposure to temps as low as 77C or 170.6F, which I would consider more than slight warming, but nonetheless good info to know about.

interesting paper. Good to know there is debate.
I do want to know though, that the parts that what you can feel are by definition at a lower temperature than the parts hidden in the structure, where heat is much less able to be transported away. The surface you feel is cooling to the air. The internal structure is doing that (cooling) much less so.

But, that paper seems good input in an apparently still ongoing debate.

 

[Corey]

Didn't see it mentioned in a quick scan of these two pages, but draft for any given chimney height will vary based on a lot of factors... the house / location its in, weather, average outdoor temps you burn in, etc.

For a single story, your 22ft might be OK, though if that is 'just' meeting clearances on a 2 story, it might be marginal and if it is a basement stove or the dreaded 'bump out' room on a 2 story, performance might not meet expectations. Also if you expect to do a lot of burning in high humidity / marginally cool temps, (say drizzly rain @ 40°F) that also lowers the draft compared to a dry 20° day.

 

[DeadTreeBurner]

interesting paper. Good to know there is debate.
I do want to know though, that the parts that what you can feel are by definition at a lower temperature than the parts hidden in the structure, where heat is much less able to be transported away. The surface you feel is cooling to the air. The internal structure is doing that (cooling) much less so.

But, that paper seems good input in an apparently still ongoing debate.

"The surface you feel is cooling to the air. The internal structure is doing that (cooling) much less so."
Very true.
Probably some sort of calculations you could do to compare nearby brickwork temps to the chimney bricks and come up with something close. Or I could bore a small hole in the rim joist where the chimney is and put a temp probe in.
The real problem is it's hard to tell what your dealing with if you weren't involved in or around for the construction of the home.
But yeah, this discussion has been educational for me.

 

[moresnow]

Another thing I have seen is structural wood framing not only in direct contact but also integrated into the masonry chimney structure in hidden locations. No joke. What were people thinking?
Things like that may have something to do with stringent code......

 

[bholler]

Another thing I have seen is structural wood framing not only in direct contact but also integrated into the masonry chimney structure in hidden locations. No joke. What were people thinking?
Things like that may have something to do with stringent code......

We see that all the time

 

[DeadTreeBurner]

Another thing I have seen is structural wood framing not only in direct contact but also integrated into the masonry chimney structure in hidden locations. No joke. What were people thinking?
Things like that may have something to do with stringent code......

People often aren't thinking and/or don't care. A significant portion of the population have an IQ just in the "below average" range and "borderline" range. Not to mention that we generally seem to have not great critical thinking skills in this country.
It's astounding the kind of shoddy work you'll see out in the real world, and companies don't particularly care as long as shoddy work doesn't become too problematic and shortcuts result in $$$ for said companies. Applies to fields from construction to software development. My dad was in construction and I've kept tabs on the work done on my roof replacement awhile back, so I've seen that side of it. I also have done software development and, well, I've seen crappy, crufty software too.

 

[moresnow]

People often aren't thinking and/or don't care. A significant portion of the population have an IQ just in the "below average" range and "borderline" range. Not to mention that we generally seem to have not great critical thinking skills in this country.
It's astounding the kind of shoddy work you'll see out in the real world, and companies don't particularly care as long as shoddy work doesn't become too problematic and shortcuts result in $$$ for said companies. Applies to fields from construction to software development. My dad was in construction and I've kept tabs on the work done on my roof replacement awhile back, so I've seen that side of it. I also have done software development and, well, I've seen crappy, crufty software too.

Agreed. This country has a problem. I'm just glad I was able to step away from the great majority of it all. Sometimes folks with the highest IQ were the toughest to talk common sense to. They just couldn't get it

 

[bholler]

Agreed. This country has a problem. I'm just glad I was able to step away from the great majority of it all. Sometimes folks with the highest IQ were the toughest to talk common sense to. They just couldn't get it

To be honest I don't see this as a common sense issue. To me it is more about understanding and trusting the testing that others have done to tell us what is the safest and best way to do things

 

[DeadTreeBurner]

To be honest I don't see this as a common sense issue. To me it is more about understanding and trusting the testing that others have done to tell us what is the safest and best way to do things

Yeah, there's the facts/data side of the equation, then the human nature part.
I only threw the IQ in there b/c there are a fair number of people out there doing work that aren't that bright and aren't supervised properly. Then you have the Dunning-Kruger effect that can come into play for folks of average and higher IQ, lack of knowledge, bias and agenda, greed, laziness and corruption. And now widespread politicization of data.
So it pays to hire a contractor/company with a good reputation/track record.