Insulation on inside of exterior masonry (brick) wall

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Old 11-03-17, 04:37 PM
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Insulation on inside of exterior masonry (brick) wall

Got a wall situation I'm not familiar with...

Tore out the old built-ins and wall around my fireplace. From outside to inside: The exterior wall is brick,then about a half inch gap, then there's a layer of weird old particle board sheathing, and touching that is the 2x4's of the inner wall, with some old black batt double faced (tar paper) wood pulp insulation.

Here's my question:
I'm going to tear out this old nasty insulation and replace it with something that hasnt been ate up by mice and fallen apart. Everything I read is contradictory as far as what type of insulation to use since the wall itself is brick... Like i said, there's a layer of what appears to be exterior sheathing between the insulation/studs and the brick wall itself. It's pretty garbage but it's there. I was leaning toward using some of the Roxul stuff since it's supposedly better with mold resistance etc. and allows moisture to travel through it, but it's been fine with double sided batts this whole time (50+ years)... plus I'd like to use something with at least a little vapor resistance for the summer. Here in IL.

Since it has that sheathing layer can I treat is as a normal wall in those areas? Or does the brick still come into play?

Planning on putting new insulation, then either drywall or wood panel and building new built-in bookshelves on that around the fireplace. Gonna frame in the fireplace separately and do a stone veneer, so basically I'm just looking at the walls on either side to insulate. All I know is this old black stuff has got to go...and I'd rather have something than nothing in that wall. Or there's always EPS? Not sure how that'd work adjacent to the sheathing though. Thanks guys.

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Old 11-03-17, 05:25 PM
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Just a couple of comments. The gap between the brick and whatever is next is necessary to allow the brick to dry. Inside that it is best to air seal as best possible, Air leakage reduced insulation value and transports moisture. Install a vapor barrier over the inside of the studs if codes require it, otherwise not necessary. Seal around electrical penetrations, up down and to the sides. I also like Roxul it fits tight and is easy to cut with a long bread knife.

Bud
 
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Old 11-04-17, 12:30 PM
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By air seal do you mean the vapor barrier? And if I added one, would it be between the insulation and the fiberboard, or between the drywall/etc and the insulation?
 
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Old 11-04-17, 03:01 PM
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An air barrier needs to be rigid and not full of miscellaneous holes, which is how most plastic coverings end up. A dozen tubes of inexpensive caulking usually does a good job of sealing every seal and crack. Not sure what the black material is, but if it will block air leakage 100% then just caulk the perimeter.

Anytime I run into questions involving brick I reference this link as I have almost zero experience in that area. Take a look and see if it helps at all.
https://buildingscience.com/document...rs?full_view=1

Bud
 
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