block off plate and insulation around insert?

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orlkc

Member
Nov 9, 2017
68
Eastern MA
I have a jotul GI 635 DV IPI insert installed in a masonry fireplace on one end of our house (wood stove is on the other end). Since I was home a lot more than normal this past winter, I noticed that it was quite cold near there when the insert isn't running. This doesn't seem surprising since it's a giant chunk of metal and brick on an outside wall.

I've read many threads here that talk about installing a block off plate, and debates around whether it's okay to put mineral wool insulation on the back and side walls of a fireplace before installing an insert. All of those threads that I could find, though, are about wood inserts. Do the same conclusions apply for gas inserts?

I read through the jotul manual, which seemed to imply that a block off plate is okay (there was mention of sealing off the flue from the house in one place), but nothing about whether insulation on the fireplace walls is acceptable. The clearance diagrams seem to say that a fireplace opening 1/8" larger than the insert on the sides and rear is acceptable. I'd have space to keep a gap much larger than that even with insulation installed.
 
Jan 9, 2017
76
Phelps NY
I have a jotul GI 635 DV IPI insert installed in a masonry fireplace on one end of our house (wood stove is on the other end). Since I was home a lot more than normal this past winter, I noticed that it was quite cold near there when the insert isn't running. This doesn't seem surprising since it's a giant chunk of metal and brick on an outside wall.

I've read many threads here that talk about installing a block off plate, and debates around whether it's okay to put mineral wool insulation on the back and side walls of a fireplace before installing an insert. All of those threads that I could find, though, are about wood inserts. Do the same conclusions apply for gas inserts?

I read through the jotul manual, which seemed to imply that a block off plate is okay (there was mention of sealing off the flue from the house in one place), but nothing about whether insulation on the fireplace walls is acceptable. The clearance diagrams seem to say that a fireplace opening 1/8" larger than the insert on the sides and rear is acceptable. I'd have space to keep a gap much larger than that even with insulation installed.
For myself, I would feel comfortable insulating it even if the manual does not say it's allowable. Just make sure it can in no way contact the blower or any controls. It also does not have to be rockwool, but if you use fiberglass insulation, make absolutely sure the paper backing does not get used, as it is made with tar and very flammable. Fiberglass insulation does not burn, but if made hot enough it will melt. I have seen fiberglass directly against the exhaust liner, and sometimes it shows signs of melting a little. Not a big deal...
 
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orlkc

Member
Nov 9, 2017
68
Eastern MA
It looks like mineral wool insulation should be easy enough to find locally, so I'll plan to proceed with that. I suspect the harder part will be pulling the insert out. We'll see how that goes.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
24,429
central pa
It looks like mineral wool insulation should be easy enough to find locally, so I'll plan to proceed with that. I suspect the harder part will be pulling the insert out. We'll see how that goes.
Use mineral wool and keep it off of the insert itself. As long as there is a bit of a gap there is no chance on it causing any issues
 

orlkc

Member
Nov 9, 2017
68
Eastern MA
I was wrong about what the hardest part would be -- leaving enough extra space (and in the correct directions) in the opening where the liners pass through the block off plate to get it all put back together again was the hardest part. But I did get it done after a few false starts. Thanks for the responses!