insulate flex liner installed inside brick chimney?

[rmcfall]

A friend of mine is putting a stainless flex liner inside his masonry chimney for a woodstove and there is some question whether he needs to insulate it or not. His chimney is constructed of at least one, but maybe two, layers of regular brick. There are no flue tiles. The chimney sits on an exterior wall, but it sits just inside a framed stud wall. Thus, you can see the brick chimney exit the roof, but it enclosed in the wood siding and framing when looking at the side of the house. Does he need to insulate the liner to prevent those studs from being exposed to too much heat over time? Again, the chimney is made up of at least one, maybe two, layers of regular brick. Also, the chimney looks to be about 12x12, so there will be some air space between the liner and the brick.

 

[recppd]

No flue tiles, eh? I don't know where you live, but I would think the insulation would be required simply to meet code in case of a chimney fire. I insulated my liner, but mine is in an exterior chimney.

 

[elkimmeg]

Because the chimney its self in in non compliance meaning no clay liner then one has to install a liner based on the liner's listing which does require insulation for compliance of its listing. I would suggest 1/2" insulation for zero clearance since wood is all around that chimney

 

[Rhone]

Yup, insulation required in unlined chimneys.

 

[wahoowad]

What is the purpose of the insulation? To deminish heat transfer to nearby combustibles, or to keep the liner warmer for improved draft?

 

[rmcfall]

Thanks everyone. That is what I figured, but I wanted to make sure before I passed on any information to my friend.

 

[DriftWood]

What is the purpose of the insulation? To diminish heat transfer to nearby combustibles, or to keep the liner warmer for improved draft?

Insulation is needed to meet code: that is to help maintain a flue temperature exceeding 250 degrees F to prevent creosote condensation in the flue pipe, on the surface inside of pipe it self, the full length of the pipe. The pipe will heat faster on startup and stay hotter longer on cool down when insulated. Creosote deposits are the problem, when they burn the fire is as hot as the fire your fire box, excess of 1,100 degrees F.!! Insulation will help protect the house from this hot uncontrolled heat when creosote burns, a chimney fire.

Wood Stove Maintenance and Operation

http://www.cdc.gov/nasd/docs/d000001-d000100/d000046/d000046.html

 

[Rhone]

What is the purpose of the insulation? To deminish heat transfer to nearby combustibles, or to keep the liner warmer for improved draft?

There's a few benefits of the insulation. In this case, with an unlined chimney there isn't sufficient protection incase of a chimney fire. The main purpose here is to confine the heat to the liner if a chimney fire occurs.

Some people who have lined and safe chimneys may choose to insulate anyway because it improves your draft because it lets your liner warm faster and maintains hotter temperatures than unlined ones. Which, results in the ability to have fires when it's warmer outside. Some people who want to have fires when it's 50F+ outside might have a hard time trying to do that without it being insulated, it depends on the situation. And last, some people use it because they know their unit will run the best with it, it's the safest route, and they like the feeling there setup couldn't be better or safer.

 

[rmcfall]

In the case of my own chimney, which is lined with clay flue tiles, I plan on insulating my liner just to improve the draft. I have seen that some insulate the TEE as well. Is this necessary/helpful?

 

[DriftWood]

In the case of my own chimney, which is lined with clay flue tiles, I plan on insulating my liner just to improve the draft. I have seen that some insulate the TEE as well. Is this necessary/helpful?

That depends on your installation if it is has good clearance to combustibles and it will be exposed to heat the room I do not insulate the T or exposed flue pipe. Flue gas in a tee is usually hot enough to keep the tee free of deposits. I run my stoves to keep flue pipe surface temperature above 250F and below 500F using a stove thermometer.

 

[rmcfall]

In my case the TEE will sort of be exposed to the room due to being a hearth mount installation. Plus, clearance isn't an issue. I guess it does make sense to leave it uninsulated to provide extra heat for the room like you said. In my friend's installation, however, I guess his tee will need to be wrapped due to the clearance concerns.

In the case of my own chimney, which is lined with clay flue tiles, I plan on insulating my liner just to improve the draft. I have seen that some insulate the TEE as well. Is this necessary/helpful?

That depends on your installation if it is has good clearance to combustibles and it will be exposed to heat the room I do not insulate T of flue pipe. Flue gas in a tee is usually hot enough to keep the tee free of deposits. I have run my stoves on flue gas temperature above 250F and below 500F.

 

[DriftWood]

In my case the TEE will sort of be exposed to the room due to being a hearth mount installation. Plus, clearance isn't an issue. I guess it does make sense to leave it uninsulated to provide extra heat for the room like you said. In my friend's installation, however, I guess his tee will need to be wrapped due to the clearance concerns.

In the case of my own chimney, which is lined with clay flue tiles, I plan on insulating my liner just to improve the draft. I have seen that some insulate the TEE as well. Is this necessary/helpful?

That depends on your installation if it is has good clearance to combustibles and it will be exposed to heat the room I do not insulate T of flue pipe. Flue gas in a tee is usually hot enough to keep the tee free of deposits. I have run my stoves on flue gas temperature above 250F and below 500F.

Paint the tee and exposed pipe with black hi-temp stove paint, they will give off more heat.

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