6" liner vs. 5.5" insulated liner?

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TooHotToTouch

New Member
Nov 6, 2021
4
Upstate NY
Hi,
I've already asked bholler for his advice which I'm grateful for but I wanted to throw it open to the whole forum. This was my original question:

"I have an 8" square ceramic chimney flue in a block chimney. I had a flexible 6" liner put in 3 years ago and I've never had worse creosote than I had last winter. 3 chimney contractors have come out: 2 want to put in a 5.5" insulated liner, and 1 wants to put in a single wall 6" liner, saying you don't want to reduce the size from the 6" stovepipe cause that will cause creosote. A big problem with the old flexi liner is there was never a connecting piece from the liner to the ceramic thimble installed and he just put some fiberglass insulation in that space between the liner and the thimble. I like the idea of the insulation and double wall of stainless steel to get the liner warm and protect the house more. Or do I do the 6" single wall and if creosote is still a problem, fill in the sides later with pearlite?"

bholler suggested breaking out the ceramic flue and putting in an insulated 6" liner. The contractor who suggested the 6" single wall also doesn't recommend going to a smaller liner to connect to the 6" stove pipe. And he agrees with bholler the only way is to break out the ceramic flue and wrap the liner with 1" insulation. Anybody else wanna weigh in? I'm especially interested in the moderators and the pros out there. Thanks!
 

john26

Minister of Fire
Oct 27, 2008
781
Wildwood MO
Good luck getting a 5.5" with insulation down an 8x8. I installed a 5.5" in a 8"x12" with a 1/4" insulation it was not easy fits very snug. If I did it over again I would break out the ceramic liner. I have a few things in my favor with the 5.5" Its strait up with a T at the bottom for easy cleaning . Liner is 30' plus 5' of stove pipe inside and it will only be used in the coldest part of winter maybe 2.5 months a year.
 

tabner

Feeling the Heat
Jan 17, 2019
299
Eastern CT
(not a Pro, but i did have the same debate during my install, so i can share some thoughts)
what is at the bottom of the chimney? Is the cleanout door well sealed? Is this chimney exterior or interior to the house?
I'm just wondering if cold air was leaking up the chimney from a cleanout door, flowing around the liner (based on the fact you said it was not a sealed off T at the liner bottom, instead it was just left wide open to the thimble). If so, correctly installing the 6" liner with a sealed off T at the bottom coming through the thimble and sealed to the stove pipe, may solve that problem.
unfortunately unless you can find a stove that gives the 5.5" option in the manual, i think you want to shy away from that option. Even though it would probably work, it may be an insurance/liability issue.
have you measured the ID of your clay tiles? how much wiggle room does the current 6" liner have? I think Rockford sells a 6" liner with 1/4" of insulation wrap. If that fits it might be a good compromise?
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
30,187
central pa
(not a Pro, but i did have the same debate during my install, so i can share some thoughts)
what is at the bottom of the chimney? Is the cleanout door well sealed? Is this chimney exterior or interior to the house?
I'm just wondering if cold air was leaking up the chimney from a cleanout door, flowing around the liner (based on the fact you said it was not a sealed off T at the liner bottom, instead it was just left wide open to the thimble). If so, correctly installing the 6" liner with a sealed off T at the bottom coming through the thimble and sealed to the stove pipe, may solve that problem.
unfortunately unless you can find a stove that gives the 5.5" option in the manual, i think you want to shy away from that option. Even though it would probably work, it may be an insurance/liability issue.
have you measured the ID of your clay tiles? how much wiggle room does the current 6" liner have? I think Rockford sells a 6" liner with 1/4" of insulation wrap. If that fits it might be a good compromise?
1/4" wrap doesn't meet code requirements. You need 1/2".
 

john26

Minister of Fire
Oct 27, 2008
781
Wildwood MO
have you measured the ID of your clay tiles? how much wiggle room does the current 6" liner have? I think Rockford sells a 6" liner with 1/4" of insulation wrap. If that fits it might be a good compromise?
That would be very tight I dragged a scrap piece of 6" through my 8x12 first barley fit.
 

TooHotToTouch

New Member
Nov 6, 2021
4
Upstate NY
@tabner It's an exterior chimney with 2 flues both 8x8, the other one for the oil burner. When I used to clean the ceramic flue myself, I used an 8" square brush and it was a tight fit but could be pulled through without too much effort. I'd say the chimney is @ 32 - 35' tall and @ 25' from the thimble to the top. There is a little play in the clean-out door and no doubt cold air is entering from top and bottom, although clearly more so from the top. I think the biggest problem with the creosote build-up was the lack of a T connector to the stove pipe. I doubt there's much wiggle room with the 6" liner in there now but I will see if it moves. Contractor says breaking out the ceramic should give us another 1 1/2" and also that 1/4" or 1/2" insulation wouldn't do much good. Should be an inch, he says.

One concern with breaking out the ceramic is doing damage to the cinder block surrounding it. I'll have to ask him how often he's had to do it.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
30,187
central pa
@tabner It's an exterior chimney with 2 flues both 8x8, the other one for the oil burner. When I used to clean the ceramic flue myself, I used an 8" square brush and it was a tight fit but could be pulled through without too much effort. I'd say the chimney is @ 32 - 35' tall and @ 25' from the thimble to the top. There is a little play in the clean-out door and no doubt cold air is entering from top and bottom, although clearly more so from the top. I think the biggest problem with the creosote build-up was the lack of a T connector to the stove pipe. I doubt there's much wiggle room with the 6" liner in there now but I will see if it moves. Contractor says breaking out the ceramic should give us another 1 1/2" and also that 1/4" or 1/2" insulation wouldn't do much good. Should be an inch, he says.

One concern with breaking out the ceramic is doing damage to the cinder block surrounding it. I'll have to ask him how often he's had to do it.
1/4" doesn't meet code requirements.

1/2" is required when clearances are not met by the chimney structure. Not sure what he means it won't do much good.

And I am not aware of any approved 1" liner insulation. I have wrapped then poured insulation though on old chimneys that could use interior stabilization.
 

SpaceBus

Minister of Fire
Nov 18, 2018
7,087
Downeast Maine
Duraliner makes an extra compact rigid 6" liner. I'm going to try and get one down my 8X8 interior clay tile liner. If it doesn't work I have no qualms removing that clay liner.
 

TooHotToTouch

New Member
Nov 6, 2021
4
Upstate NY
1/2" is required when clearances are not met by the chimney structure. Not sure what he means it won't do much good.

And I am not aware of any approved 1" liner insulation. I have wrapped then poured insulation though on old chimneys that could use interior stabilization.
I think he was implying that 1/2" wouldn't keep the liner warm. I think he mentioned wrapping it and then covering it with a sock or something. It wouldn't be 2 separate pieces of stainless steel.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
30,187
central pa
I think he was implying that 1/2" wouldn't keep the liner warm. I think he mentioned wrapping it and then covering it with a sock or something. It wouldn't be 2 separate pieces of stainless steel.
Yes you wrap it with 1/2" then cover with stainless mesh. That is the recommended and approved method