# Masonry Chimney getting hot to the touch after new insert installed.



## WI Deer Slayer (Nov 4, 2012)

Hello,

Long time lurker, first time poster. I am new to wood burning and am a little nervous after a recent discovery. We just purchased a new home and had a chimney sweep come over to sweep and inspect the chimney before we started using it for the year. After cleaning it, he discovered a small hole in the back of the smoke box and rusting, probably due to the fact that the previous owners never had a rain cap on. So after some research and his reccomendation, I decided to purchase an insert. I purchased a new Pacific Energy super 27 insert to install in my existing fireplace, and he reccommended that I put in a fully insulated liner, but he would have to remove my terra cota flue tiles to make it fit. I was fine with this and actually wanted the fully insulated zero clearance liner, but he couldnt get me into the schedule for a few weeks, so I decided to go with a different company who installed a S.S. flex liner with no insulation but left the flue tiles in. The dealer told me that being an interior chimney there was no need to have a insulate liner and it was actually a waste. They just put insulation in the top of the flue and bottom around the insert to keep the heat in. So after burning now for about five days, the mechanical room behind the fireplace which has the masonry chimney that goes up to the roof has been getting warm. So I put my hand on the back side of the chimney, which is just four inch block with the terra cota flue tile inside, it is very warm. It is an interior chimney obviously, but my question is how dangerous is this? I can hold my hand on the block but it is almost to the point where i cant for more than a minute or so. It goes up through the ceiling into the attic and then out the roof, but I am just worried where it goes through the ceiling, if it will heat the wood joists up so much it could possibly ignite them. I am kind of freaking out a little guys as this cost me almost 4,000 dollars to have installed, and I am wondering if I made a mistake by not having the first sweep install it with the fully insulated liner. The fire has been burning for almost five days now, so I realize the flue will probably not get any hotter, but it just makes me nervous having the back side of the block that warm. If anybody has any experience with this, or knows if it should be getting warm to the touch, or if 4 inch block with a terra cota flue liner is even sufficient for a masonry fireplace, I would appreciate any advice. Sorry for rambling so much and thanks in advance.


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## Fred Wright (Nov 4, 2012)

Don't feed that fire any more. Have a pro come out and look it over first. 

The chimney block should never be so hot you can't hold your hand on it. From what you describe, it sounds like the flex liner was closed off top and bottom, trapping heated air in the flue around it.


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## greenskeeper (Nov 4, 2012)

Get a temp gun and see what the actual temp of the chimney is.

My insert will heat the masonry chimney and hearth to where it will melt candles (ask my wife about that). 

I'm not concerned at all, the insert is holding more heat in your house which is a good thing.


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## allstihl (Nov 4, 2012)

hot is a relative thing. if you cant hold your hand on it stop burning and get pro advice.


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## brenndatomu (Nov 4, 2012)

I agree, should get it checked. FYI, your SS flex liner can be pulled out, insulated, then reinstalled.


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## mga (Nov 4, 2012)

the bricks on the front of my fireplace get real hot. been that way for as long as i have been burning wood.....never had an issue. in fact, they generate heat long after the fire has gone out, so, i'm kinda good with that.

where i did have a problem was in the attic. the mason blocks would get warm and throw some heat off, causing snow to melt and creating icicles. so, i wrapped those blocks with 3.5" of insulation and that problem was solved.

how was your fireplace designed?


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## stihl023/5 (Nov 4, 2012)

Get it checked asap, and by someone other than the one who installed it. Better to be safe than without a home. My parents had a masonry chimney light little damage but a pita.


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## WI Deer Slayer (Nov 4, 2012)

Thanks for the reply guys. 

I have a large fire stoked right now and its warm, but you can hold your hand on it, I may have exaggerated a little that I cant hold my hand on it, I just want to be on the safe side. I am going to call the installer tomorrow to see what his thoughts are, but it sounds like other people have the masonry fireplaces warm up to. I am just curious if I do have it pulled out and insulated, is a little bit of insulation enough to stop that much heat from coming through the liner into the masonry?


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## H-Ranch (Nov 4, 2012)

As a general rule of thumb I use 150F to be too hot to touch for more than an instant. If you can hold your hand on it for up to a minute then I would guess it's less than that.

If it's hot where it passes through the ceiling or you think it could be too hot in the attic then it's best to have it checked by a professional. Definitely worth the call to put your mind at ease - if he still has questions then an inspection is worth it for peace of mind.


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## WI Deer Slayer (Nov 4, 2012)

As far as the actual temperature of the block, my hot water lines from my boiler are 150 degrees and I cant hold my hand on them. So as far as my masonry, I would estimate the hottest I have felt it is probably somewhere in the 120 degree range. Do others on this site experience there chimneys getting this warm even with a liner in? Also, is 120 degrees at hottest dangerous enough to warrant pulling out the liner and having it insulated? 

-Thanks


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## russhd1997 (Nov 4, 2012)

I had a lined cinder block chimney in my old house. The chimney got warm enough to heat the second floor. Never worried about it and didn't burn the house down either.


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## Ductape (Nov 4, 2012)

120 isn't going to burn your house down. How hot do you suppose your roof gets with the sun beating on it in the summer.

Get an inexpensive infrared non-contact thermometer and find out what the actual temp is.


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## Ductape (Nov 4, 2012)

Just for fun, I went a shot a dozen spots on my chimney with my IR thermometer. Our house was built in 1888 and has a single layer brick chimney with a stainless flex liner with a vermiculite/mortar insulation poured around the liner. I had no problem finding spots that were 131 degrees. I really wouldn't be in a panic if your confident you are in the 120 range. There are plenty of places that sell inexpensive IR thermometers, such as Harbor Freight.


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## stihly dan (Nov 4, 2012)

Insulate the chimney in the attic so you don't get ice dam's, or condensation up there. I think that should be your greatest concern.


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## darkbyrd (Nov 4, 2012)

Doesn't sound like it is too hot, but if you had a chimney fire, all bets are off. I'd consider getting the chimney insulated.


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## woodfarmer (Nov 6, 2012)

Masonry chimneys require an airspace of minimum 1" to combustibles all the way around, so there should be no wood framing touching the chimney. That would be my only major concern


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## mga (Nov 6, 2012)

WI Deer Slayer said:


> Thanks for the reply guys.
> 
> I have a large fire stoked right now and its warm, but you can hold your hand on it, I may have exaggerated a little that I cant hold my hand on it, I just want to be on the safe side. I am going to call the installer tomorrow to see what his thoughts are, but it sounds like other people have the masonry fireplaces warm up to. I am just curious if I do have it pulled out and insulated, is a little bit of insulation enough to stop that much heat from coming through the liner into the masonry?



generally they will pour vermiculite to insulate the liner.

the purpose of doing this is to ensure the liner will remain hot, therefore, not allowing a build up of creosote inside of it. inserts will create more creosote because you can damper them down so much.

whether it keeps your masonry from getting hot or not is determined by how much insulation you have.

right now, the bricks in the front of my fire place are hot...you can't leave your hand on them. been that way for 30 years.


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## taskswap (Nov 6, 2012)

I have the pour-down type of insulation around my chimney liner, and I'm really happy with its performance. It's vermiculite and a small amount of portland cement - real dusty to work with until you wet it down, which you only do to "a little damp" (it's not like concrete). It pours down easily, although I wish I had mixed it on the roof. Getting it up there in buckets was a pain.

Still, it was easier than working with an insulation blanket and worrying about getting a hole in that somewhere. Whoever built my chimney didn't set the flue tiles perfectly straight, and the offsets would have made it a real job to get a liner plus blanket in properly. This also fills the corners, so it seems like it would insulate better than just the blanket. I dunno, but it's an exterior chimney (no other choice) and it drafts fine and doesn't seem to build much creosote. I have a boiler with hot water storage so I tend to run pretty hot anyway, but I'm happy with it.

I don't know how the safety factor works out but it seems like even if there was a pinhole or hot spot in the liner somewhere, this stuff would protect the chimney, no?


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## wagz (Nov 6, 2012)

i'd be careful messing w/ vermiculite. some of the types of that have asbestos in it. deadlly...


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