Insulating an uninsulated liner

[burntime]

I am not bad with heights, check the O.D. of the liner, do you have a 6 or 5.5? Had the installers done a 5.5 you would be in much better shape??? Is there a lot of mortor between joints? If there is you are stuck, if not you have a chance. It will be finese and finagle (sp) but it cold be done. With the liner you know it is covered...pouring and you still may be touching the terra-cotta.

 

[Wet1]

I am not bad with heights, check the O.D. of the liner, do you have a 6 or 5.5? Had the installers done a 5.5 you would be in much better shape??? Is there a lot of mortor between joints? If there is you are stuck, if not you have a chance. It will be finese and finagle (sp) but it cold be done. With the liner you know it is covered...pouring and you still may be touching the terra-cotta.

6". I honestly haven't been able to get up high enough to really see down that flue. I know there's mortar sticking out from the bricks where it's not lined toward the base, but I have no idea what the clay joints look like. I agree that the SS liner will still likely be touching in spots if the insulation is poured, but I can't imagine the contact area would be enough to actually worry about if everything else is insulated. I guess I'm going to to have to get up there and survey it and the base real well to see what my best angle of attack should be. Thanks again...

 

[oconnor]

What insulation is used and sold with the commercially available SS flex liner kits?

It is rockwool that is 1/2 inch thick if I remember right, then there is a foil face on it.

That makes sense. How is it attached and joined around the length of the liner? I have a 35' 6" liner I need to do, but the ID of the flue is only 7" so I'm concerned about the fit.

Thanks.

Actually, it isn't rockwool or mineral wool at all, it is ceramic wool, like KAOWOOL or many other brands. As I mentioned in another post, rockwool/mineral wool doesn't pass the chimney fire burn test that is part of UL1777/CAN635.

If rockwool could pass the testing for liners, I'm sure someone would market it for liners, as it is cheaper, and less hazardous to the user, but I haven't found anyone marketing it for use around liners yet.

Attaching the ceramic wool blanket usually involves clamps or a wire mesh sock system, and some high temp tape. Keep in mind, the only approved way to insulate a liner is to follow the instructions of the liner manufacturer. If they didn't test thier liner with insulation, then there won't be an approved way to insulate it.

That doesn't mean that what you do won't work, just that it isn't tested. Testing is what insurance companies and code inspectors should be concerned with. If those aren't concerns in your case, then any ceramic wool product that the manufacturer states can withstand the constant 1200*F exposure, and the 2100*F exposure for 60 mins in a chimney fire should suffice. (Numbers I use are Canadian specs - they are hotter and longer than the US numbers, but not by much)

 

[oconnor]

When the liner goes into servicable clay tiles, then insulation is merely a performance/size issue, as the tiles and chimney already need to meet code requirements for clearances. If the chimney meets code but is just too large ID of the tiles, then touching the tiles shouldn't be a problem.

However, if the tiles aren't servicable, or the chimney doesn't have the air space clearances (1 or 2 inches, it depends) outside the chimney to combustibles, then most manufacturers will give you a Zero/Zero clearance rating on an insulated liner - zero clearance needed inside between the liner and masonary, and zero clearance outside between chimney and combustibles.

That is what I consider the best advantage about insulating a flue, as it makes air sealing and insulating the house a whole lot simpler.

 

[Todd]

Why do you have to insulate your liner? Is your chimney in bad shape or have no clay tiles? I think insuating a liner is a waste of money unless your chimney is in bad shape.

 

[Wet1]

Why do you have to insulate your liner? Is your chimney in bad shape or have no clay tiles? I think insuating a liner is a waste of money unless your chimney is in bad shape.

If this question is directed to me, my chimney is in bad shape. It's an interior chimney and I have no idea how close or well spaced the interior combustible walls covering it up through the 3 levels are. I also know the clay liner that I can see from the top is in bad shape. I also have no idea how far the clay goes down, but I don't think it goes all the way to the bottom (although it could. In actuality, I suspect the just an uninsulated SS liner inside the existing chimney would offer enough protection in the even of a chimney fire, but I'd feel better knowing it was insulated for that extra (and proper) protection, plus I'm sure the insurance company would agree. As far as draft goes, there's plenty w/o any insulation.

 

[noviceinsertuser]

I originally posted the question so if the question is for me..... I guess I felt after reading several threads on here that it would not only offer protection but help in the efficiency of the stove. I have an interior chimney that isn't in too bad of shape. I'm new to all of this though. It's interesting to hear that you feel it is a waste of money...just curious why?

 

[burntime]

Novice, I used to think the same thing until I was getting ice damning on my roof because I was heating my interior masonary chimney and heating the attic. I can tell you from someone that had the set-up both ways that not only is the performance a lot better, but after seeing it installed both ways (I reinstalled the liner) that I sleep better at night with the liner. My chimney is in great shape, but for a few hundred bucks to improve efficiency on a 5k stove why wouldn't you?

 

[Todd]

Ok, never thought of ice damning problems. That would be a good reason to insulate the liner. I'm just saying if your chimney tall enough, in good shape, and interior, it will probably draft very well without the extra insulation. I have an outside wall 23' brick chimney with s/s uninsulated liner and draft is so good I had to install a pipe damper to slow it down and I also have two 90 degree elbows in my system.

 

[oconnor]

The Chimney Safety Instutute of America and the National Fireplace Institute made insulating chimney liners one of their 6 Best Practices, right before "following instructions and using parts correctly". The point they make is that if you don't know with certainty the condition of a chimney, then insulating it mitigates the risk of unknown defects.

That said, I am still waiting for my installer to come back and do mine.... I guess I'll call him again today, it has been 4 months since they put it in.