single vs double wall liner, buck 27000

broken08

New Member
Jan 21, 2020
7
80454
Hey all,
I got an old buck 27000 and thanks to your advice in a previous post, I've learned that using it as designed, as a slammer, is not so good. So I'm looking to get a liner installed. I had a chimney guy come out and he said I have so much creosote in the masonry chimney that it would cost almost $2000 to remove! So it's time for a liner. He gave me a good price to install a flexible stainless liner, (less than the massive cleaning). He thinks 6", single wall is what I need. I know a lot of people are discussing the insulated double wall though. I've also read some people are stuffing insulation around their liner in the chimney?? Why?

Is he wrong in his choice? Why do I need the insulation? I have a large cinder block chimney run, straight up about 25 feet.

I also want to make sure that the liner we use is future proof for when I upgrade to a newer stove in a year or two.

Thanks!
 

Leiper

New Member
Feb 5, 2020
28
S-KY
People are trying to keep the inside liner warmer all the way up by insulating and/or using double liner to keep creosote from forming as much because cooling temps up higher.Sounds to me like you might have to remove some creosote before installing a single liner if there is as much buildup as you say. The single pipe won’t have the clearance to combustibles the double will ,might heat up the creosote and you don’t want that,I run double wall on a FPX about 26 or so feet in a chase the outer liner on it uses outside air pulling it in around the stove cooling the stove down some then sending warmer air up between the two pipes and out. Good luck
 

BigJ273

Burning Hunk
Feb 15, 2015
142
Maryland
You still need to have the creosote removed, before installing the liner. With the temps in the flue, it could still ignite, even with a liner. The insulation is wrapped around the liner to keep the flue gasses at the right temp till they exit at the top. Otherwise they could cool too much causing the creation of creosote, especially towards the top, which is the coldest spot. It could also effect the draft. I definitely recommend insulating the liner. As for single or double, I think either would be fine. Just my two cents
 
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begreen

Mooderator
Staff member
Nov 18, 2005
81,123
South Puget Sound, WA
The creosote must be removed first. Then an insulated liner needs to be installed. It can be externally wrapped with insulation or the insulation can be part of the liner. Often the latter is done when clearances for the liner are a tight fit.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
20,589
central pa
Hey all,
I got an old buck 27000 and thanks to your advice in a previous post, I've learned that using it as designed, as a slammer, is not so good. So I'm looking to get a liner installed. I had a chimney guy come out and he said I have so much creosote in the masonry chimney that it would cost almost $2000 to remove! So it's time for a liner. He gave me a good price to install a flexible stainless liner, (less than the massive cleaning). He thinks 6", single wall is what I need. I know a lot of people are discussing the insulated double wall though. I've also read some people are stuffing insulation around their liner in the chimney?? Why?

Is he wrong in his choice? Why do I need the insulation? I have a large cinder block chimney run, straight up about 25 feet.

I also want to make sure that the liner we use is future proof for when I upgrade to a newer stove in a year or two.

Thanks!
Don't let him do the job. Installing a liner does not mean the creosote doesn't need removed. You also need an 8" liner not 6". And it needs insulated.
 

Socratic Monologue

Burning Hunk
Dec 2, 2009
170
WI
I also want to make sure that the liner we use is future proof for when I upgrade to a newer stove in a year or two.
If your current stove needs an 8", that might be a future issue; lots of stoves require 6", I think.

I guess my thought is that if you're going to replace the stove in a year, it may be simpler/cheaper to replace it at the same time as the liner.
 
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coaly

Fisher Moderator
Staff member
Dec 22, 2007
3,711
NE PA
Why do I need the insulation? I have a large cinder block chimney run, straight up about 25 feet.

I also want to make sure that the liner we use is future proof for when I upgrade to a newer stove in a year or two.
The reason for insulation is keeping it hotter inside without wasting fuel to keep it hot. The object is keeping the internal flue temp above 250*f. all the way to the top. This is while smoke is present. Water vapor from combustion condenses on flue walls below that temperature, allowing smoke particles to stick. This is creosote. In the coaling stage, there is no creosote formation so the chimney and pipe can be cooler. By keeping a thermometer on your connector pipe, you can judge how hot the inside is. The surface temp of single wall pipe is about 1/2 the inside temp. So double your temperature reading on the pipe before it goes into chimney. It is then a guess as to how much it cools to the top. The better the flue is insulated, the hotter it stays inside without burning so hard to keep it clean. Saving fuel. The best is using an IR thermometer about a foot down on the wall from the top to get a temp reading to coordinate with your bottom reading so you have a good idea of flue temp near the top. You can see how an indoor chimney stays much warmer than an exterior chimney exposed to cold wind.
Most newer stoves use 6 inch. I'm not familiar with using your Buck with a 6, it is also against code to reduce, but some physically work fine reduced. The resistance in the system such as connector pipe, els, tee, spark screen, all add to resistance. The more resistance, the less draft, so the smaller chimney is affected more. I would be tempted to try an insulated 6 inch liner with what you have. It won't give you full BTU output reduced, but most stoves are seldom used at maximum capacity. You may experience smoke roll in opening doors with a smaller flue, again a lot of factors to consider including firebox design.
A larger chimney doesn't draft easier, it has more capacity which also requires more heat to make that larger capacity work.
The difference between 6 and 8 is a lot. 8 inch is almost twice the area inside as 6, so it takes that much more heat to keep it above the required 250*.
 

coaly

Fisher Moderator
Staff member
Dec 22, 2007
3,711
NE PA
Your zip code being in Colorado may be an indication of higher elevation above 5 or 6000 feet. That can be another factor in the size flue you need. What is your elevation?
Do you know the outlet measurement of the stove, and the measurement of the chimney flue? (area or diameter)
 
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broken08

New Member
Jan 21, 2020
7
80454
t won't give you full BTU output
Your zip code being in Colorado may be an indication of higher elevation above 5 or 6000 feet. That can be another factor in the size flue you need. What is your elevation?
Do you know the outlet measurement of the stove, and the measurement of the chimney flue? (area or diameter)
I'm up at 7200 feet elevation. The stove has a rectangular 4x8 outlet.
 

broken08

New Member
Jan 21, 2020
7
80454
I called a certified tech at woodland direct, he stated I do not need (or in his opinion need to worry about) insulation for my liner.
This seems to be the problem I'm running in to; a lot of (random) people say I need insulation, but now two certified fireplace techs from different places both say I don't.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
20,589
central pa
I called a certified tech at woodland direct, he stated I do not need (or in his opinion need to worry about) insulation for my liner.
This seems to be the problem I'm running in to; a lot of (random) people say I need insulation, but now two certified fireplace techs from different places both say I don't.
Did any of these "certified techs" check to see if you have the required clearance from the outside of the masonry structure to any combustible materials? If not they have no way to say you don't need insulation.

Here is the applicable code which tells you what clearances are required

 
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bholler

Chimney sweep
Staff member
Jan 14, 2014
20,589
central pa
Did those guys say why they thought you didn't need insulation? Or why the one guy thought there was no need to remove the creosote before lining the chimney?
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
20,589
central pa
The applicable code is 1003.18. it is there because in a chimney fire enough heat can transfer through the masonry to ignite adjacent combustibles. This gets more dangerous over time as those materials pyrolize
 

coaly

Fisher Moderator
Staff member
Dec 22, 2007
3,711
NE PA
As bholler mentioned, a call on the phone isn't looking at the chimney. Most chimneys were built against structural members (or less than 12" from flue to combustible material) so they need that insulated liner for safety reasons, not to make it work.

Technically the 32 square inch outlet on the stove would be reduced to 28.28 using 6 inch flue. I wouldn't be concerned about performance loss with that small of a reduction. If there were elbows, horizontal pipe, or more resistance in the system, all reducing draft, that could be an issue. The higher elevation requires a stronger drafting chimney than at sea level. As an example a 12 foot chimney at sea level is equivalent to a 15.5 foot chimney at 7000-8000 feet. (measured from stove top to top of chimney) So your height is more than enough to produce the required draft. A new stove will give you the minimum height you need in the installation manual. A block off plate top and bottom prevents moving air from cooling an uninsulated liner, but it is still will not stay as hot as insulated.

Since you're now aware the object is to keep the flue temp above 250* to the top, efficiency is doing that with as much loss as possible. A liner without insulation needs you to burn the fire hotter, giving it more air to leave more heat up the chimney, providing enough heat to the top. This uses more fuel allowing more heat up. Just like insulating walls to keep heat in, the insulated liner saves fuel over time making it a very smart investment. It also saves cleaning the flue as frequently. This stove will benefit with an insulated liner, but a newer stove may require it. (or at least need it even more)
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
20,589
central pa
As bholler mentioned, a call on the phone isn't looking at the chimney. Most chimneys were built against structural members (or less than 12" from flue to combustible material) so they need that insulated liner for safety reasons, not to make it work.

Technically the 32 square inch outlet on the stove would be reduced to 28.28 using 6 inch flue. I wouldn't be concerned about performance loss with that small of a reduction. If there were elbows, horizontal pipe, or more resistance in the system, all reducing draft, that could be an issue. The higher elevation requires a stronger drafting chimney than at sea level. As an example a 12 foot chimney at sea level is equivalent to a 15.5 foot chimney at 7000-8000 feet. (measured from stove top to top of chimney) So your height is more than enough to produce the required draft. A new stove will give you the minimum height you need in the installation manual. A block off plate top and bottom prevents moving air from cooling an uninsulated liner, but it is still will not stay as hot as insulated.

Since you're now aware the object is to keep the flue temp above 250* to the top, efficiency is doing that with as much loss as possible. A liner without insulation needs you to burn the fire hotter, giving it more air to leave more heat up the chimney, providing enough heat to the top. This uses more fuel allowing more heat up. Just like insulating walls to keep heat in, the insulated liner saves fuel over time making it a very smart investment. It also saves cleaning the flue as frequently. This stove will benefit with an insulated liner, but a newer stove may require it. (or at least need it even more)
You are so much more diplomatic about it than me. Well said and thank you.
 
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bholler

Chimney sweep
Staff member
Jan 14, 2014
20,589
central pa
GREAT info, thanks all. Ok I'll insulate and be done with it. And yes the one tech looked at my chimney and said not to insulate.
He was also the one who wanted $2000 to clean it and said you didn't need to clean it before lining it right?

I mean if it's that bad I would just break out the clay. That wouldn't cost anywhere near $2000
 

coaly

Fisher Moderator
Staff member
Dec 22, 2007
3,711
NE PA
You are so much more diplomatic about it than me. Well said and thank you.
If I wasn't afraid of ladders you'd have competition. I'm the guy at the bottom and have eaten enough soot.
 
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coaly

Fisher Moderator
Staff member
Dec 22, 2007
3,711
NE PA
GREAT info, thanks all. Ok I'll insulate and be done with it. And yes the one tech looked at my chimney and said not to insulate.
Does he sell firewood?
 
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