Uninsulated liner not to code?

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Abrahampost

New Member
Sep 8, 2021
5
Vermont
Thanks in advance for the advice.

I have a VT castings Aspen stove on a 25ft exterior chimney(masonry chimney with clay tiled flue) that was installed in 2019 with an uninsulated heavy duty flex liner.

We have had no issues with draft and the first year cleaning went fine and found no issues with the setup. Fast-forward to this season and the same company found issues with the install and recommends a ton of work.

My questions are, is it against fire codes to not have an insulated liner? If my draft is fine and I clean yearly is my current setup sufficient?

My annoyance level is a bit high on this one since the company inspected the same setup in 2020 and deemed it perfectly fine, now wants to do 4k worth if work to install a new liner with insulation. This was not a diy install, the stove supplier installed the system.

Also, a bit unrelated they broke my refractory baffle and tore the superwool in the stove during the cleaning, neither issue is has been addressed by them.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
30,269
central pa
Thanks in advance for the advice.

I have a VT castings Aspen stove on a 25ft exterior chimney(masonry chimney with clay tiled flue) that was installed in 2019 with an uninsulated heavy duty flex liner.

We have had no issues with draft and the first year cleaning went fine and found no issues with the setup. Fast-forward to this season and the same company found issues with the install and recommends a ton of work.

My questions are, is it against fire codes to not have an insulated liner? If my draft is fine and I clean yearly is my current setup sufficient?

My annoyance level is a bit high on this one since the company inspected the same setup in 2020 and deemed it perfectly fine, now wants to do 4k worth if work to install a new liner with insulation. This was not a diy install, the stove supplier installed the system.

Also, a bit unrelated they broke my refractory baffle and tore the superwool in the stove during the cleaning, neither issue is has been addressed by them.
Inn general yes most of the time insulation is required to meet code. But it depends upon a few factors.

1. Does your chimney being an exterior one have the required 1" clearance from the outer masonry surface to combustible materials.

2. Was the liner tested and specified for use with solid fuel appliances without insulation?
 
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fireboss1237

Member
Nov 25, 2015
42
Dillsburg PA
Inn general yes most of the time insulation is required to meet code. But it depends upon a few factors.

1. Does your chimney being an exterior one have the required 1" clearance from the outer masonry surface to combustible materials.

2. Was the liner tested and specified for use with solid fuel appliances without insulation?
How coinvent that you are from Central PA, I'm outside Harrisburg and am installing a 6" Rockford Flexible Stainless steel liner myself for a brand new Blaze King woodstove . I had a professional come out to clean and inspect my chimney today, I watched the inspection video as he ran it through the flue. Found some glazing and one bad mortar join. No problem, I want to be safe, I agreed to pay to fix the problems. But he said the liner needs to be insulated, I called the liner company prior to todays cleaning and ask about an insulated blanket. They asked about my chimney and flue design, told them 7" interior diameter Terracotta lined with a cinder block and brick structure. All the literature I found in a 15 minute google search says as long as liner is designed for solid burning fuel and 2" away from any combustible material insulation isn't needed. What's the truth and what exactly is the correct code?

Now I can add insulation blanket myself, but the gentleman said that'd he or I would need to knock out the old tile to fit the 6" liner + insulation, I just want to know the true code. I'm not trying to buy a new house if something goes wrong and the home insurance wont pay for it.
 

stoveliker

Minister of Fire
Nov 17, 2019
6,313
Long Island NY
The outside of the masonry chimney needs to be two inch from combustibles (when inside the home; for an outside chimney it needs to be one inch). The brick therefore does not count in the clearance distance needed for the liner.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
30,269
central pa
How coinvent that you are from Central PA, I'm outside Harrisburg and am installing a 6" Rockford Flexible Stainless steel liner myself for a brand new Blaze King woodstove . I had a professional come out to clean and inspect my chimney today, I watched the inspection video as he ran it through the flue. Found some glazing and one bad mortar join. No problem, I want to be safe, I agreed to pay to fix the problems. But he said the liner needs to be insulated, I called the liner company prior to todays cleaning and ask about an insulated blanket. They asked about my chimney and flue design, told them 7" interior diameter Terracotta lined with a cinder block and brick structure. All the literature I found in a 15 minute google search says as long as liner is designed for solid burning fuel and 2" away from any combustible material insulation isn't needed. What's the truth and what exactly is the correct code?

Now I can add insulation blanket myself, but the gentleman said that'd he or I would need to knock out the old tile to fit the 6" liner + insulation, I just want to know the true code. I'm not trying to buy a new house if something goes wrong and the home insurance wont pay for it.
Code says exactly what stove like said above. An interior chimney needs 2" clearance from the outside of the masonry an exterior one needs 1" and yes the clay will need to be removed. We do go almost to Harrisburg but don't have an opening untill almost November now
 

fireboss1237

Member
Nov 25, 2015
42
Dillsburg PA
Code says exactly what stove like said above. An interior chimney needs 2" clearance from the outside of the masonry an exterior one needs 1" and yes the clay will need to be removed. We do go almost to Harrisburg but don't have an opening untill almost November now
So as described the interior chimney is the flue correct? If so a cinder block and standard brick is way more than 2" from combustible. materials. I don't see why I would need insulation blanket?
 

stoveliker

Minister of Fire
Nov 17, 2019
6,313
Long Island NY
I think not.
It's flue liner + masonry or block + 2".before combustibles. Only if you have the two inch is it correct.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
30,269
central pa
So as described the interior chimney is the flue correct? If so a cinder block and standard brick is way more than 2" from combustible. materials. I don't see why I would need insulation blanket?
No the outside of the masonry structure needs to be 2" away from any combustible materials.

An interior vs exterior chimney is in reference to the whether the chimney is inside the structure of the house or outside.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
30,269
central pa
Here is the diagram from the code book

0-0-0-301.jpg
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
30,269
central pa
Then I think I'm good to go
So you have a 2" space between the outer layer of masonry and any combustible materials?

Honestly even if you do the performance gains from insulation are worth it.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
30,269
central pa
Thanks so much, this helps. Not sure about the airspace. My outside brick touches my roof with flashing obviously, but with the cider block I still don't' see how there is any danger of getting too hot on the outside
It's about heat transfer through the masonry causing pyrolysis over time
 

Rickb

Minister of Fire
Oct 24, 2012
1,213
St.Louis
Id be surprised.... most do not have the clearances. Even if they do you have to be able to prove it. Again its 1 inch on exterior chimney. That's 1 inch from any masonry structure of your chimney before there is anything combustible....

That said if you dont want to knock out the old liner why not do a 5.5 inch liner with insulation?
 

fireboss1237

Member
Nov 25, 2015
42
Dillsburg PA
Id be surprised.... most do not have the clearances. Even if they do you have to be able to prove it. Again its 1 inch on exterior chimney. That's 1 inch from any masonry structure of your chimney before there is anything combustible....

That said if you dont want to knock out the old liner why not do a 5.5 inch liner with insulation?
I thought about it, but my outlet of my stove is 6 inches, was trying to avoid adapters. Also need to look into return policy
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
30,269
central pa
5.5 probably won't fit insulated either
 
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BKVP

Minister of Fire
The outside of the masonry chimney needs to be two inch from combustibles (when inside the home; for an outside chimney it needs to be one inch). The brick therefore does not count in the clearance distance needed for the liner.
Opposite clearances. 2" inside, 1" outside.
 
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stoveliker

Minister of Fire
Nov 17, 2019
6,313
Long Island NY
Opposite clearances. 2" inside, 1" outside.
I think I wrote it correctly; the *outside of the masonry chimney* needs 2" when it is inside the home and 1" when it is outside the home.

At least that is what I meant. It may be confusing to use "outside" for the location of the chimney AND the location of the clearance.
 
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Highbeam

Minister of Fire
Dec 28, 2006
20,017
Mt. Rainier Foothills, WA
On top of the chimney clearance issues, don’t some liner manufacturers just flat out require insulation for wood heating?
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
30,269
central pa
On top of the chimney clearance issues, don’t some liner manufacturers just flat out require insulation for wood heating?
I don't know of any that require it but many strongly recommend it.
 

EbS-P

Minister of Fire
Jan 19, 2019
3,573
SE North Carolina
Ok thanks, this is turning out to be really annoying
can you look at it in the attic? It’s a good place. Roof sheeting and framing are easily visible.
 

BigJ273

Minister of Fire
Feb 15, 2015
577
Maryland
I’ve always said I find it hard to believe that no combustible materials (sheathing, shingles, etc) touch the chimney. Especially now a days where things get thrown together so sloppy. I believe in a prior post bhollar stated the insulated liner negates this one inch. Which makes sense.