Chimney Liner Alternatives...Please help!

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What should we do?

  • Smash out the terracotta and go wrapped flex.

    Votes: 1 33.3%

  • Leave the terracotta and pour in insulation around flex.

    Votes: 2 66.7%
  • Total voters
    3
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A

avc8130

Minister of Fire
Dec 6, 2010
1,049
God's Gift to Gassification
I'm helping a buddy install a wood stove in his traditional masonry fireplace. He understands it is best to install an insulated liner and wants to do everything tip top best.

We checked his current flue tonight and we have our first hurdle.

The current flue is terracotta liner. Inside dimensions are 6.5 x 11.5 rectangular.

The stove he has chosen requires a 6" flue.

His idea is to smash out all of the terracotta tile and install a traditional flex liner with wrap insulation.

I think we should leave the terracotta lining since it is in good shape and run a flex liner with pour in Vermiculite insulation.

Is one plan better than the other?

Thanks for the quick help!

ac
 
From what I understand it looks like the 6.5" width may restrict the insulation on the flex. I suppose either option may work, not sure which will ease the workload or the pocketbook better.
 
That's pretty short for a modern stove. Is he considering extending this to at least 14-16ft? What stove?
 
what part of the country do you guys live?
 
I just installed a flex liner from Rockford Chimney supply that was a 6 inch with the wrap insulation. My terra cotta was 7 inch inside and it was a VERY tight fit, mainly due to the old clay liner pieces didn't match up quite right and kept catching on the clamp holding the snout on to the liner. Being its not that tall of a run I would probably bust out the terra cotta and put an insulated flex liner in. Just my opinion though.
 
avc8130 said:
Yes. I am working on convincing him to add a 4' piece of rigid to the top of whatever we do.

ac
Click to expand...
Since its only 12' tall it would be easy to wreck that clay outa there! It usually takes less time to remove than starting a hearth.com thread!;)
As for extending the flue, it would be a real good idea. You might consider using a piece of insulated chimney as the extension. You could possibly use a class A anchor plate with the liner attached to the bottom side and class A extending up a few feet. If its not insulated it will build creosote like crazy up there in the wind.
 
I've never tried to knock out terracotta liner. It just had the initial reaction of possibly opening a can of worms to me.

I can't find any information about how thick pour in insulation should be. Anyone know?

ac
 
I am the naysayer I guess. Use poured in insulation. Bust those tiles out of there and you ain't gonna believe what happens when you try to sell that house to somebody that doesn't want a wood stove in that fireplace.
 
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You said it was a fireplace install, what kind of stove is going in?
If its a fireplace, then pouring in the insulation is pretty tough. You will have to completely block the flue at the throat, otherwise you are just filling the smoke chamber up with insulation. It must be completely blocked, if not it will find its way out. I wouldn't recommend it.
 
BrotherBart said:
I am the naysayer I guess. Use poured in insulation. Bust those tiles out of there and you ain't gonna believe what happens when you try to sell that house to somebody that doesn't want a wood stove in that fireplace.
Click to expand...

That was my main argument. I liked that leaving the terracotta in place at least left the option of reverse.

ac
 
webby3650 said:
You said it was a fireplace install, what kind of stove is going in?
If its a fireplace, then pouring in the insulation is pretty tough. You will have to completely block the flue at the throat, otherwise you are just filling the smoke chamber up with insulation. It must be completely blocked, if not it will find its way out. I wouldn't recommend it.
Click to expand...

I read that a "chimney balloon" was used for that purpose?

ac
 
Frankly you guys have pretty much the same weather as we do and my two un-insulated liners in tile lined chimneys rock. At least they have for the last seven years.

The most important stuff happens down at the bottom. Good stove, dry wood and good burning habits.
 
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BrotherBart said:
I am the naysayer I guess. Use poured in insulation. Bust those tiles out of there and you ain't gonna believe what happens when you try to sell that house to somebody that doesn't want a wood stove in that fireplace.
Click to expand...
You have a good point. The oval flex would be best, if your up to the cost!
 
avc8130 said:
I read that a "chimney balloon" was used for that purpose?

ac
Click to expand...

Wrong. You need a tight block off plate. You use chimney balloon to block the flue in an unused fireplace.
 
BrotherBart said:
Wrong. You need a tight block off plate. You use chimney balloon to block the flue in an unused fireplace.
Click to expand...

Maybe you misunderstood what I meant. I thought a chimney balloon was used while insulating to control the insulation and keep it out of the smoke chamber.

At least that is what I read on Rockford (one of the sponsors here):

"Note: A chimney balloon is the best solution to stop the insulation mix from leaking into your fireplace or down into your cleanout door at the base of your chimney. The chimney balloon should be removed, once the insulation mix has cured, before a fire is lit in the chimney."

ac
 
avc8130 said:
That was my main argument. I liked that leaving the terracotta in place at least left the option of reverse.

ac
Click to expand...
If reversal is a possibility, then either an uninsulated liner or a preinsulated oval is what you need. A poured in mix is gonna be a huge mess if you try to remove it in the future.
 
avc8130 said:
Maybe you misunderstood what I meant. I thought a chimney balloon was used while insulating to control the insulation and keep it out of the smoke chamber.

At least that is what I read on Rockford (one of the sponsors here):

"Note: A chimney balloon is the best solution to stop the insulation mix from leaking into your fireplace or down into your cleanout door at the base of your chimney. The chimney balloon should be removed, once the insulation mix has cured, before a fire is lit in the chimney."

ac
Click to expand...
How does the liner pass through the balloon? You liner is coming all the way to the stove.
 
webby3650 said:
If reversal is a possibility, then either an uninsulated liner or a preinsulated oval is what you need. A poured in mix is gonna be a huge mess if you try to remove it in the future.
Click to expand...

Come on, I can hear the realtor now:

"The old flue is still intact, just pull out the liner and remove the insulation and you have a beautiful rustic fireplace." LOL

ac
 
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You need to use a poured in loose fill like Perlite. If you are going to use something that is a poured in slush mix like Thermix that hardens then you have the same problem later. You ain't gonna get it or the liner out of there.
 
Leave the tile there. It is a good backup if something ever happed to the flex liner. Buy an ovalized flex liner (with insulation wrap) or make your own. I have seen several videos on youtube from liner Mfgs on ovalizing liners. I think some will even sell you the tool to do it. Wouldn't be too hard to make one though...

I agree, dont use the poured insulation, it would be expensive on that big of a chimney, and semi permanent.
 
Last edited:
webby3650 said:
How does the liner pass through the balloon? You liner is coming all the way to the stove.
Click to expand...

Like I said, never done it before. I see your point. I have a head cold and have some pretty odd brain activity these past 3 days. LOL

Does it even matter? Is a 6" liner in a 6.5" wide flue a REAL possibility?

In other words, would it matter that the insulation may be thin to non-existant at some points?

ac
 
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