Uninsulated Liner?

[tabner]

Before everyone tells me what a terrible idea an uninsulated liner is, please hear me out.

My chimney is 8" square terracotta (single flue) inside masonry chimney. Interior chimney. It goes up from finished basement through two full floors, an attic, and out the peak. From thimble to cap it's got to be around 30'. I have checked on all floors and i DO have the 2" of clearance to combustibles all the way up. Actually more like 4" from what i can see. Plus aluminum flashing up against the masonry in between floors, which I think is a fire stop that code requires.
Photos of my flue are below. bholler was nice enough to comment one time, and said this looked OK (perhaps missing some mortar?) combined with the height of the thing and being interior to the house, i should have plenty of draft.
with that said, i have two kids, and I'm a person who worries. These tiles are 30 years old, and I think I'd sleep better knowing there was a liner in there. Since i have all summer to work on it (currently not burning), and a 26% tax credit, I'm tempted to throw a 6" flex liner in there, even though I probably don't need it per code, but just to be safe. It's easier to do now, rather than later.
So my questions:
Will a 6" flex, without insulation fit? It is a straight shot, but as you can see from the pics, over 30 feet it's not perfectly straight, is this going to be a groan? (i really don't want to bust 30 feet of tiles, if I can avoid it) (have to have a T on the bottom, which i think increases OD to 6.5"?)
Can i skip the insulation since i'm 30 feet inside the house? (plus from a safety standpoint i have terracotta, masonry, and required clearances)
Am i over thinking it? Should i skip the liner and just see how well the terracotta drafts?

Thanks

 

[tabner]

Little more info. I just measured to be exact. Inside of terracotta measures 7.5" square. Thimble to cap is 26 feet.

 

[Caw]

I cant comment on the state of your chimney itself but I can tell you about my setup which works very well for me:

I burn an Osburn 1600 insert on the 1st floor of my house. Its partially protruding with a 24' straight shot up the exterior dual flue chimney. My terracotta was in good shape but I never considered running the stove without a liner...that's a big no-no. That said, getting a 6" liner down was a very tight squeeze due to a piece of rogue mortar halfway down so I have a standard non-insulated liner.

It kind of goes against the grain here as most will recommend an insulated liner whenever possible, especially on an exterior chimney, but it has worked for me so I thought I'd share. I simply didn't have room for it. The terracotta/liner combo plus new stove and good draft works. My first cleaning after months of burning turned up next to nothing. My little 1.85 cu Ozzy cruises at 600-650 and fully heats my 1600 two-story cape down to about 5 degrees before it needs help. My house is on the upper end of the recommended sq footage for the stove and where I live we don't see those temps consistently too often, 1-2 weeks a year sporadically maybe, so I'm happy with the performance.

Bottom line - definitely get some form of liner. The rest I leave up to the pros!

 

[tabner]

I cant comment on the state of your chimney itself but I can tell you about my setup which works very well for me:

I burn an Osburn 1600 insert on the 1st floor of my house. Its partially protruding with a 24' straight shot up the exterior dual flue chimney. My terracotta was in good shape but I never considered running the stove without a liner...that's a big no-no. That said, getting a 6" liner down was a very tight squeeze due to a piece of rogue mortar halfway down so I have a standard non-insulated liner.

It kind of goes against the grain here as most will recommend an insulated liner whenever possible, especially on an exterior chimney, but it has worked for me so I thought I'd share. I simply didn't have room for it. The terracotta/liner combo plus new stove and good draft works. My first cleaning after months of burning turned up next to nothing. My little 1.85 cu Ozzy cruises at 600-650 and fully heats my 1600 two-story cape down to about 5 degrees before it needs help. My house is on the upper end of the recommended sq footage for the stove and where I live we don't see those temps consistently too often, 1-2 weeks a year sporadically maybe, so I'm happy with the performance.

Bottom line - definitely get some form of liner. The rest I leave up to the pros!

View attachment 275717

Awesome, thanks for the feedback, and love the doggo!

 

[Bad LP]

I’m having no issues with a non insulated liner in a 16 year old interior chimney of same size but starts on first floor.

 

[tabner]

I’m having no issues with a non insulated liner in a 16 year old interior chimney of same size but starts on first floor.

Thanks. Was it fairly easy to get in?

 

[gthomas785]

The insulation requirement actually relates to the clearance to combustibles on the outside of the chimney, you need 2" all the way around it everywhere. No framing, drywall, wood, etc within 2" of the masonry. If you have that, then you can use an uninsulated liner. With 30' I don't think you'd have any performance issues due to lack of insulation. Possibly too much draft.

 

[bholler]

The insulation requirement actually relates to the clearance to combustibles on the outside of the chimney, you need 2" all the way around it everywhere. No framing, drywall, wood, etc within 2" of the masonry. If you have that, then you can use an uninsulated liner. With 30' I don't think you'd have any performance issues due to lack of insulation. Possibly too much draft.

And excessive cooling by the time it gets to the top.

 

[john26]

There a re a few stove out there that allow 5.5" liners that would help reduce draft as well my guess is that maybe helpful.

 

[Bad LP]

Thanks. Was it fairly easy to get in?

I didn’t install it. I don’t do 12:12 roof climbing.

 

[tabner]

Cool, thanks for all the input. I think because almost the entire chimney is inside the house (only about 3 feet above the peak, and the attic is more of a crawl space), I'm going to give the uninsulated 6" a shot. (i had noticed the 5.5" online but my stove's manual doesn't list it).
I'm glad I slowed down and decided to ask. Definitely going to feel more confident with a liner in there.
Crazy to think I had two sweeps out and neither of them checked my chimney inside for clearances, and neither quoted a liner.
@bholler if I get the "Rock-Flex 316Ti flex stainless" that Rockford Chimney supply sells, is that an acceptable one?
They describe it as: "Fabricated in 316Ti stainless steel, with 7 ply seams and 10 corrugations per seam"

 

[Bad LP]

Cool, thanks for all the input. I think because almost the entire chimney is inside the house (only about 3 feet above the peak, and the attic is more of a crawl space), I'm going to give the uninsulated 6" a shot. (i had noticed the 5.5" online but my stove's manual doesn't list it).
I'm glad I slowed down and decided to ask. Definitely going to feel more confident with a liner in there.
Crazy to think I had two sweeps out and neither of them checked my chimney inside for clearances, and neither quoted a liner.
@bholler if I get the "Rock-Flex 316Ti flex stainless" that Rockford Chimney supply sells, is that an acceptable one?
They describe it as: "Fabricated in 316Ti stainless steel, with 7 ply seams and 10 corrugations per seam"

With your chimney passing thru an attic I'd go with an insulated liner. My chimney is in conditioned space up to the roof penetration so my application is a little bit different.
I think it would suck if you had to remove it for build up in that cold space.

 

[coreboy83]

I have zero issues with our uninsulated liner. 19' masonry flue, through the garage. My Pacific Energy burns hot enough to keep it hot all the way up

 

[tabner]

With your chimney passing thru an attic I'd go with an insulated liner. My chimney is in conditioned space up to the roof penetration so my application is a little bit different.
I think it would suck if you had to remove it for build up in that cold space.

yeah, redoing it would suck. Of the 26 feet, about 4 feet are in the attic and about 3 above the peak. So i definitely have a solid 19 feet or so inside the house. Can I fit it down my terracotta with the insulation? I'm hoping to avoid smashing tiles down 30 feet (30 feet cause thimble to the cleanout is another 4 feet).

 

[gthomas785]

With 8" square you should be able to fit a 6" with insulation. Even if not, I'd go with an insulated 5.5" over an uninsulated 6". More for safety than performance.

Edit to say I have a 25 foot 5.5" liner and it sucks like a vacuum cleaner. So if you're worried about reduced draft from 5.5" don't be.

 

[brenndatomu]

Can I fit it down my terracotta with the insulation?

Use 1/4" insulation instead of the usual 1/2"?
Or a pre-insulated liner...they tend to be a bit smaller OD than a standard liner with insulation blanket...a little tougher too

 

[Gearhead660]

If your chimney is 8" square, you could still run an insulated liner. I Got a pre insulated 6" liner from Rockford, it was 7" OD. If going with 5.5" with your stove is an option, it should fit.

 

[tabner]

With 8" square you should be able to fit a 6" with insulation. Even if not, I'd go with an insulated 5.5" over an uninsulated 6". More for safety than performance.

Edit to say I have a 25 foot 5.5" liner and it sucks like a vacuum cleaner. So if you're worried about reduced draft from 5.5" don't be.

the tiles measure 7.5" square inside. Did your stove manual say the 5.5" was acceptable? or did you just wing it?
i just emailed heartstone tech to see what they think of the 5.5".

 

[gthomas785]

the tiles measure 7.5" square inside. Did your stove manual say the 5.5" was acceptable? or did you just wing it?
i just emailed heartstone tech to see what they think of the 5.5".

I believe it called for 6", however in my case I had no choice, the 5.5 was the only way it would fit.
The stove also calls for a listed chimney liner, which an uninsulated liner usually is not.

As I said before, unless you have 2" of clearance around the masonry everywhere (including ceiling / roof pass throughs) an uninsulated liner on a wood burning appliance is a code violation and could set your house on fire if you have a chimney fire. I know plenty of people who have uninsulated liners and for the most part they are safe as long as you don't have a chimney fire. But nobody ever plans to have one

 

[tabner]

I believe it called for 6", however in my case I had no choice, the 5.5 was the only way it would fit.
The stove also calls for a listed chimney liner, which an uninsulated liner usually is not.

As I said before, unless you have 2" of clearance around the masonry everywhere (including ceiling / roof pass throughs) an uninsulated liner on a wood burning appliance is a code violation and could set your house on fire if you have a chimney fire. I know plenty of people who have uninsulated liners and for the most part they are safe as long as you don't have a chimney fire. But nobody ever plans to have one

understood, thanks. I am aware of the 2" clearance requirement. I have it, all the way up. I'm all for doing the insulation, i just don't want to get the thing stuck halfway down my chimney and spend 3 days smashing tiles, when realistically we're talking a stainless liner, then terracotta, then masonry, then 4" of clearance all the way up. I agree with your 5.5" suggestion, with insulation that sucker has got to pull plenty of draft, so logically it seems fine. I would just be concerned since it wasn't specifically OK'd in my manual i could void some warranty, or create an insurance liability there too.
at this point i'm thinking the 6" liner with 1/4" insulation - this should be a 7" OD. theoretically that should fit, and be pretty safe.

 

[gthomas785]

Ok then it should be good. I just wanted to be clear that an uninsulated liner can be just as much if not more of an insurance liability than an improperly sized one. But it sounds like yours will meet code.

 

[bholler]

understood, thanks. I am aware of the 2" clearance requirement. I have it, all the way up. I'm all for doing the insulation, i just don't want to get the thing stuck halfway down my chimney and spend 3 days smashing tiles, when realistically we're talking a stainless liner, then terracotta, then masonry, then 4" of clearance all the way up. I agree with your 5.5" suggestion, with insulation that sucker has got to pull plenty of draft, so logically it seems fine. I would just be concerned since it wasn't specifically OK'd in my manual i could void some warranty, or create an insurance liability there too.
at this point i'm thinking the 6" liner with 1/4" insulation - this should be a 7" OD. theoretically that should fit, and be pretty safe.

Because you have the required clearance I would say drop a bare liner if it will fit (which is questionable) and pour in insulation mix.

 

[davo1028]

I have a picture that might be of interest. This is my new chimney liner after about two months of burning. Picture is taken from inside my insert with baffle removed. You can clearly see where the uninsulated adapter is by the small soot buildup and where the insulation starts the chimney liner is very clean. So this is inside the house just above the insert. Of course, the effect of lack of insulation will be worse at the top of the chimney. Maybe you can make up for it with sweeping more often, but at the very least I thought this picture is very telling.

Also, I would strongly consider downsizing to the 5.5" liner, both to help with fitting insulation and to prevent over drafting. 30' is a lot of chimney. I have 25' insulated exterior chimney and have a lot of draft, definitely more than desired any time the temp is below freezing outside. This is on a Drolet 1400i, so 1.9 cu ft firebox, secondary burn tubes, no cat.

 

[tabner]

I have a picture that might be of interest. This is my new chimney liner after about two months of burning. Picture is taken from inside my insert with baffle removed. You can clearly see where the uninsulated adapter is by the small soot buildup and where the insulation starts the chimney liner is very clean. So this is inside the house just above the insert. Of course, the effect of lack of insulation will be worse at the top of the chimney. Maybe you can make up for it with sweeping more often, but at the very least I thought this picture is very telling.

Also, I would strongly consider downsizing to the 5.5" liner, both to help with fitting insulation and to prevent over drafting. 30' is a lot of chimney. I have 25' insulated exterior chimney and have a lot of draft, definitely more than desired any time the temp is below freezing outside. This is on a Drolet 1400i, so 1.9 cu ft firebox, secondary burn tubes, no cat.

View attachment 275854

Thanks Davo! I definitely like the idea of dropping down to 5.5", it would make my life easier. But until i get it in writing from Hearthstone i'm hesitant. I feel like this forum has taught me, from clearances, to hearth pads, to min chimney heights - don't deviate from the stove's manual. I would just be afraid of increasing my liability.
I'm not super worried about excess draft - i am putting in a key damper, and i have two 90s in the stove pipe to overcome, so i would rather have too much draft than not enough.
i emailed hearthstone, i'll certainly update this forum if i get a response from them.

 

[davo1028]

Thanks Davo! I definitely like the idea of dropping down to 5.5", it would make my life easier. But until i get it in writing from Hearthstone i'm hesitant. I feel like this forum has taught me, from clearances, to hearth pads, to min chimney heights - don't deviate from the stove's manual. I would just be afraid of increasing my liability.
I'm not super worried about excess draft - i am putting in a key damper, and i have two 90s in the stove pipe to overcome, so i would rather have too much draft than not enough.
i emailed hearthstone, i'll certainly update this forum if i get a response from them.

You're certainly doing the right thing checking in with the manufacturer about the liner size. And if you add the key damper, that would probably negate the need for a 5.5" from a draft standpoint, as well as let you use the full 6" for creating more draft in conditions when you might want it (mild weather, for example).