what exactly is the safety issue.......

[JoeRJGR]

of not insulating your SS liner?

Thanks!

 

[jotulguy]

A flue that cools to quickly will produce creosote. Also depending on your chimney and fuel smoke in the home. An insulated liner stays warmer and warms faster.

 

[pen]

If your reason for lining is that your existing chimney has cracked tiles, then you are lining because your original chimney is no longer acceptable for protecting you from a chimney fire. As a result, you need to insulate the original chimney from the heat contained inside of your SS liner or else heat (not flames, but heat) has the potential of escaping your liner, penetrating the original chimney, and causing you the big problem that you were trying to avoid.

My chimney wasn't large enough for stuffing an insulated liner down it so I spent 16 bucks on a 4 cu foot bag of vermiculite and insulated around my SS liner w/ that.

If your chimney was perfect, and COMPLETELY clean after a thorough sweeping, and is an interior chimney I would say that you could get away w/out insulating. However, if it were me, for the small amount it costs, I'd insulate it anyway. If your chimney isn't as perfect as I just mentioned, then I'd suggest that insulation is not an optional thing, but completely necessary. Especially if you are like me and can gain a better drafting chimney w/ an added layer of protection for less than the cost of a case of beer or a good steak, it's a no-brainer. If you go fiberglass or have a larger diameter orig chimney that requires more vermiculite or perlite, then it's still cheaper than the cost of dinner for 2 and a drink. The dinner and drink would only last a few hours, you'll have this liner 25+++ years.

pen

 

[EatenByLimestone]

If your teracotta liner is cracked, you need to have an insulated liner. The thought behind this is creosote could have worked it's way into the crack and might ignite if it got too hot. Insulation might keep this from happening.

Matt

 

[begreen]

In addition to the excellent performance benefits, as I understand it, the primary safety issue is transfer of heat from the liner through the masonry to adjacent combustibles. This is particularly important in the case of an overfire or chimney fire. But because of pyrolysis reduction the ignition temp of wood, even regular burning can benefit from the insulation. The problem is that most chimneys are supposed to have a set air space from any combustibles. But very often, the chimney brick or block is in direct contact with the surrounding structure. Masonry is pretty good at transferring heat. So if the liner is cruising at 700F for hours, it is very conceivable that the surrounding wood can eventually get above ignition temperature. When that will happen depends on the construction of the chimney and structure.

Can something bad happen?, definitely. We have seen evidence of close calls here. Will it happen to your setup? Hard to say. But experience has shown me that very often shortcuts are taken in construction, especially when they are buried out of sight.

 

[nola mike]

In addition to the excellent performance benefits, as I understand it, the primary safety issue is transfer of heat from the liner through the masonry to adjacent combustibles. This is particularly important in the case of an overfire or chimney fire. But because of pyrolysis reduction the ignition temp of wood, even regular burning can benefit from the insulation. The problem is that most chimneys are supposed to have a set air space from any combustibles. But very often, the chimney brick or block is in direct contact with the surrounding structure. Masonry is pretty good at transferring heat. So if the liner is cruising at 700F for hours, it is very conceivable that the surrounding wood can eventually get above ignition temperature. When that will happen depends on the construction of the chimney and structure.

Can something bad happen?, definitely. We have seen evidence of close calls here. Will it happen to your setup? Hard to say. But experience has shown me that very often shortcuts are taken in construction, especially when they are buried out of sight.

ya know, this has got me thinking now. i'm in an old (1915) house with a questionable chimney (masonry, unlined). I put in a ss liner, cleaned the old chimney before hand, but have been nervous. Now i'm thinking that my house has brick walls, and plaster directly on the brick. Really nothing combustible at all through the length of the chimney. maybe the roof trusses i guess, but that's a ways from the stove. I feel better now.

 

[pen]

ya know, this has got me thinking now. i'm in an old (1915) house with a questionable chimney (masonry, unlined). I put in a ss liner, cleaned the old chimney before hand, but have been nervous. Now i'm thinking that my house has brick walls, and plaster directly on the brick. Really nothing combustible at all through the length of the chimney. maybe the roof trusses i guess, but that's a ways from the stove. I feel better now.

:smirk:

Is that a question? Statement? Or are we talking to ourselves again???

pen

 

[nola mike]

I'll go with "thinking aloud, keyboard dangerously close at hand, wife's in bed, no one else to listen to my ramblings". Is that an option?

 

[JoeRJGR]

All,


From a combustabilty issue, I think I am in OK shape as well. The entire wall in which the fireplace is set is brick as is the chimney...

I do have one question about the cresole issue whne a liner is not insulated. Fro what I have read, the issue is the liner hotand then cooling and form water inside the liner. However, just like the stove doesn't go from 600 degress to zero quickly....why would the liner? Wouldn't it be a more gradual process?

Thanks

 

[woodchip]

Strange thing is that over the channel from us in France, they have had a totally different attitude to flues on woodburners.

The flues have liners, but no insulation. They have an air inlet in the register plate (flue block off plate), and an outlet upstairs which has a fan and pipes to the different bedrooms.

Nice simple way of heating upstairs, but I suspect they burn mostly really old oak there, and they probably sweep quite regularly too

 

[EatenByLimestone]

Stoves have the benefit of thermal mass surrounding a bed of coals. Chimneys don't... especially outside ones that have the wind whipping around them.


Woodchip,

I imagine we'd sweep more if we had nifty songs to go along with it too:

http://www.youtube.com/watch?v=VX4Ppm-cPZI


Matt

 

[JoeRJGR]

So guys,

After lookingat my pics, would agree that from a combustability standpoint I am probably in pretty good shape?

Brother Bart - Your Bio has got to be one of the funniest things I have read in a really long time....

 

[oconnor]

So guys,

After lookingat my pics, would agree that from a combustability standpoint I am probably in pretty good shape?

Brother Bart - Your Bio has got to be one of the funniest things I have read in a really long time....

Possibly, but somewhere in that construction, you are very likely to find wood adjacent to bricks that are adjacent to the flue tiles.

Unless you are CERTAIN (i.e. you built the chimney and fireplace yourself) that there is an air gap between the firebox / chimney bricks and adjacent combustibles, you should insulate the liner. It may all look like brick form the outside, but when you strip it down, you would be surprised what you will find. In my case, we found a 2x6 adjacent to the throat of the fireplace. When the chimney is on an outside wall, it is very difficult to have an air gap between the brick and combustibles and not have a hole in the wall

 

[JoeRJGR]

[Possibly, but somewhere in that construction, you are very likely to find wood adjacent to bricks that are adjacent to the flue tiles.

Unless you are CERTAIN (i.e. you built the chimney and fireplace yourself) that there is an air gap between the firebox / chimney bricks and adjacent combustibles, you should insulate the liner. It may all look like brick form the outside, but when you strip it down, you would be surprised what you will find. In my case, we found a 2x6 adjacent to the throat of the fireplace. When the chimney is on an outside wall, it is very difficult to have an air gap between the brick and combustibles and not have a hole in the wall [/quote]


You mean you think there could be combustables between the brick on the outside and inside wall? I guess the on the second floor the chminey butts up against wood somewhere...

 

[pen]

He's saying there is a good chance that it could be a large brick facade w/ studs behind / in it. I've seen it before. Not saying that is what is happening here, but that is one heck of a lot of bricks. I'd be surprised it it were completely solid from side to side, front to back.

pen

 

[JoeRJGR]

HHHmmmm,

If I look in the chimney from the bottom, I can see the curve of the left outside wall. You cant see it in the picture I posted of the outside of the chimney, but it basically has a bottle shape to it....it gets wider toward the bottom of the house. Anyway, I can see that curve from the inside of the chimney. That chimney actually has 3 flues in it...2 for fireplaces, one for the heater vent...

Thanks again for the info....I'll probably insulate anyway just to be safe...