Dry pour insulation?

[rhaspyhonker]

Hi, I'm new here to the forum. I'm gonna pour dry thermix into my 8x8 clay tile flue. I am installing a smooth single wall 6" round liner in the flue, first. Will the thermix be of any insulation value in its dry, sand like state? I have a central (center of house) chimney with 3 flues, 2 are not used. 4" or more masonry in the chimney walls, an airspace inside that, then the 8x8 (o.d.) clay tile, dry thermix and a stainless smooth wall liner. Thoughts? Also, where's the best place to buy thermix in Ohio?

 

[all night moe]

I didn't think a centralized chimney would need insulation. I'm under the impression it benefits an exterior chimney more so.
Unless there are other reasons? @bholler

 

[bholler]

Hi, I'm new here to the forum. I'm gonna pour dry thermix into my 8x8 clay tile flue. I am installing a smooth single wall 6" round liner in the flue, first. Will the thermix be of any insulation value in its dry, sand like state? I have a central (center of house) chimney with 3 flues, 2 are not used. 4" or more masonry in the chimney walls, an airspace inside that, then the 8x8 (o.d.) clay tile, dry thermix and a stainless smooth wall liner. Thoughts? Also, where's the best place to buy thermix in Ohio?

It can't be dry it will just settle to the bottom and pack in. You also don't have enough room for the required 1" of pour in insulation.

Are you referring to the light wall 2ply smoothwall liner? I would suggest you reconsider if that is the case

 

[bholler]

I didn't think a centralized chimney would need insulation. I'm under the impression it benefits an exterior chimney more so.
Unless there are other reasons? @bholler

Yes insulation is actually more important from a safety standpoint on internal chimneys. Internal ones require 2" of clearance to combustibles which they never have

 

[rhaspyhonker]

My liner is from Rockford chimney supply...the premium smooth single layer liner. My wife heard about the vermiculite and wanted that extra layer of protection. However I just found out it's super expensive. Plus nobody around here carries it. So I'm putting in the liner as is, no insulation, just clay tiles and airspace and 4.5" of brick around that. For the little bit we are gonna use this stove, I'm not worried.

 

[bholler]

My liner is from Rockford chimney supply...the premium smooth single layer liner. My wife heard about the vermiculite and wanted that extra layer of protection. However I just found out it's super expensive. Plus nobody around here carries it. So I'm putting in the liner as is, no insulation, just clay tiles and airspace and 4.5" of brick around that. For the little bit we are gonna use this stove, I'm not worried.

It doesn't meet minimum code.

 

[rhaspyhonker]

What does the code say specifically? Where can I find that in writing?

 

[bholler]

What does the code say specifically? Where can I find that in writing?

Chapter 10 of IRC explains the required clearances for masonry chimneys serving solid fuel appliances.

For an internal chimney you need 2" clearance between the outside of the chimney structure and any combustible materials. Unless you have that your current chimney isn't code compliant and when you install a new liner you are required to bring it up to code

 

[bholler]

1001.15 Chimney clearances. Any portion of a masonry chimney located in the interior of the building or within the exterior wall of the building shall have a minimum air space clearance to combustibles of 2 inches (51 mm). Chimneys located entirely outside the exterior walls of the building, including chimneys that pass through the soffit or cornice, shall have a minimum air space clearance of 1 inch (25 mm). Sheathing materials shall be be permitted to abut the masonry chimney walls. The juncture of the sheathing materials and the chimney walls shall be sealed by methods approved by the code official. See Figure XXX. The air space shall not be filled, except to provide firestopping in accordance with Section 602.8.
When masonry chimneys are constructed as part of masonry walls or reinforced concrete walls, combustible materials shall not be in contact with the masonry wall less than 12 inches (306 mm) from the inside surface of the nearest flue lining.

Exception: Masonry chimneys equipped with a chimney lining system listed and labeled for use in chimneys in contact with combustibles in accordance with UL 1777, and installed in accordance with the manufacturer's installation instructions, are permitted to have combustible material in contact with their exterior surfaces. However, this shall not eliminate the requirement for noncombustible firestopping

 

[ExxWhy]

Not shooting the messenger in case it comes out that way, inquiring minds just wanna know.

I'm kind of curious about the science and testing behind this. So let's say you have a chimney built out of bricks back in the 60's, lined with clay tiles and connected to an old school fireplace. It's all perfectly fine to continue using it like that. But if you run a SS liner down the same chimney, it somehow becomes unsafe (from a code perspective) if the liner doesn't have an inch or 2 of clearance around it? I'm just wondering how hot can the bricks possibly get? Is it mainly in case of a chimney fire? Did they do actual testing on this?

I knocked out the clay tiles in mine, ran a 6" flexible-ish liner down it and filled as best I could with the pour in insulation. The way the liner sits in the chimney, it is undoubtedly touching the sides in various spots, but didn't see any way around it. I'm using mine with a boiler with low flue temps. (400 or less)

I bought my insulation at Rockford Chimney supply, but it's been 4 or 5 years ago.

 

[bholler]

Not shooting the messenger in case it comes out that way, inquiring minds just wanna know.

I'm kind of curious about the science and testing behind this. So let's say you have a chimney built out of bricks back in the 60's, lined with clay tiles and connected to an old school fireplace. It's all perfectly fine to continue using it like that. But if you run a SS liner down the same chimney, it somehow becomes unsafe (from a code perspective) if the liner doesn't have an inch or 2 of clearance around it? I'm just wondering how hot can the bricks possibly get? Is it mainly in case of a chimney fire? Did they do actual testing on this?

I knocked out the clay tiles in mine, ran a 6" flexible-ish liner down it and filled as best I could with the pour in insulation. The way the liner sits in the chimney, it is undoubtedly touching the sides in various spots, but didn't see any way around it. I'm using mine with a boiler with low flue temps. (400 or less)

I bought my insulation at Rockford Chimney supply, but it's been 4 or 5 years ago.

From a code perspective the clay lined chimney without clearances is not fine. It absolutely doesn't meet code and becomes more of a safety issue the longer it is used due to pyrolization of that wood contacting the masonry. It's just that you aren't required to fix it until you make a change. When installing a new liner at that point your work is required to meet code.

 

[mellow]

I think @bholler posted pictures the other day of a chimney where they took the crown off of and you could see the wood framing sitting right next to the terracotta, you couldn't see that from the outside so with pyrolysis from heat happening on that wood it was a fire waiting to happen someday, maybe would take a chimney fire to ignite it but the chances are still there. Just trying to keep you safe.

 

[bholler]

I think @bholler posted pictures the other day of a chimney where they took the crown off of and you could see the wood framing sitting right next to the terracotta, you couldn't see that from the outside so with pyrolysis from heat happening on that wood it was a fire waiting to happen someday, maybe would take a chimney fire to ignite it but the chances are still there. Just trying to keep you safe.

Yes and in that case no guarantee that an insulated liner would be enough. But it's certainly better with insulation