Can I use XPS here...

andrelaplume2November 18, 2011

Insulating Rim joists in the final section of my basemet. Using 2" foamboard with drywall in front of it. I am to a point where my upstairs fireplace is above. I pulled out the insulation I put in loosely 5 years ago...immediate draft. When I look up I see what appears to be 6' of cinder blocks..cant tell the depth. I assume this is in someway the base of the fireplace above. I have no idea if this is typical for fireplaces but want to know:

1) if the fg insulation in there is / was safe having there.

2) If I should cut a 18" x 72" piece of 2" foamboard and put it in there then cover with a piece of drywall.

My concern is the heat from the fireplace above...do the cinderblocks heat up etc....

Thoughts....

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Older homes are so variable I would take the safer route using mineral wool insulation and fireproof caulking. Roxul, for instance, can tolerate temps up to 2,150 F.

A friend had a fire in his wall while using the fireplace on his upscale 1932 home. The fireplace, it turned out, was designed only for decorative fires of an hour or so and his was burning for eight hours. The fire fighters told him this was common.

    Bookmark   November 19, 2011 at 9:20AM
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andrelaplume2

my home is 24 years old. We do not have roxul around here so far as I know...PA, USA......I had fg in there for 5 years....crap!

I can caulk w/fp caulk...big gaps though....might cost big $$$$$

The fp was wood burning...we put a vent free log set in. If you leave the flue closed it get warns the first floor great but it smells and then the stat never goes off so the upstairs gets cold...we knew all this going in...usually use it with the flew open a bit...adds some warmth but mostly used for ambience...

See picture looking up...any other thoughts....

    Bookmark   November 19, 2011 at 11:34AM
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I asume that's the view looking up. So there are firebricks on top, maybe cement too. If it's safe enough for lumber next to the blocks, it should be safe enough for XPS.

    Bookmark   November 19, 2011 at 1:30PM
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