Using fire block spray foam to seal faceplate in Fisher Fireplace Insert?

[vt-new-fp]

I have a Fisher Fireplace Insert. The fireplace opening is very large so a friend extended the original faceplate so that it would fit over the opening. It made a big difference in making the heat come into the room and not go up the chimney. However, it's not tight-tight against the uneven stone front of the fireplace. I put some rockwool and fiberglass insulation in some of the slots, but there are still big gaps. There's fireblock sprayfoam you can get that's rated to go up to the outside of chimneys in interior applications (like where an attic floor meets a chimney). I was thinking of using that instead of the loose insulation to get a better fit. Do you experts foresee any trouble with that?

 

[bholler]

I have a Fisher Fireplace Insert. The fireplace opening is very large so a friend extended the original faceplate so that it would fit over the opening. It made a big difference in making the heat come into the room and not go up the chimney. However, it's not tight-tight against the uneven stone front of the fireplace. I put some rockwool and fiberglass insulation in some of the slots, but there are still big gaps. There's fireblock sprayfoam you can get that's rated to go up to the outside of chimneys in interior applications (like where an attic floor meets a chimney). I was thinking of using that instead of the loose insulation to get a better fit. Do you experts foresee any trouble with that? View attachment 315800View attachment 315801

No absolutely do not use any spray foam in that location

 

[coaly]

Is there a block off plate at bottom of flue?

 

[vt-new-fp]

I don't know. It's a heatolater (c. 1940s, I think) - they cut into the cast iron of the heatolater to get the stainless liner up there and put some rockwool around where the collar and liner went up through the heatolater to the flue. There's that collar thing around the top opening of the stove.

 

[vt-new-fp]

No absolutely do not use any spray foam in that location

What can I use instead to get the faceplate to snug up against the stone surround? I found someone (not on hearth.com) suggesting high-temp seals with high temp adhesive: https://www.mcmaster.com/products/high-temperature-seals/ and https://www.mcmaster.com/products/high-temperature-sealants/ but I don't know which sort of seal to choose. One gap is really large.

 

[bholler]

What can I use instead to get the faceplate to snug up against the stone surround? I found someone (not on hearth.com) suggesting high-temp seals with high temp adhesive: https://www.mcmaster.com/products/high-temperature-seals/ and https://www.mcmaster.com/products/high-temperature-sealants/ but I don't know which sort of seal to choose. One gap is really large.

I wouldn't bother with anything if you have a good block off plate it won't matter at all