Interior Rigid Foam on Solid Masonry Walls–Am I Going to be Okay?
I have bought a home with solid masonry walls (CMU block interior wythe, concrete “crick” exterior wythe, plaster on the interior of the wall). I would like to add rigid foam insulation to the interior, with a gypsum board interior finish. The foam would be 1.5″ XPS (caulk around sheet perimeter, foam and/or tape between sheets) , then 3/4″ furring strips 24″OC, affixed with Tapcons to the block, with 3/4″ XPS between the furring strips. Attach drywall to the furring strips.
The home is near Dayton, Oh (extreme southern part of Zone 5).
I’ve read the helpful article by Martin Holladay regarding the issues/potential pitfalls of interior insulation of brick buildings (https://www.greenbuildingadvisor.com/blogs/dept/musings/insulating-old-brick-buildings), and some other studies/articles on the subject. For my little project (a modest 1200 SF house), I just can’t justify the expense of having a consultant come look at the project to evaluate the bricks, etc. I’m not interested in maximizing the insulation, I’m okay with staying well clear of any danger zone (of keeping the bricks too wet/cold and inviting damage) if I can still significantly improve the efficiency/comfort of the present approx. R-2 solid walls..
My question: Is it likely this R-10 of interior foam will put the masonry at risk?
– It’s not especially cold here,
– The exterior “bricks” are painted (reduced wetting/absorption?)
– The masonry appears to be in good shape. There are a few places where small bits of mortar are coming loose (house built in 1950), but things are generally in good shape. A chimney needed to be rebuilt, but it was due to its location at the eaves/lack of a cricket/and poor flashing, and water intrusion.
– The windows/lintels look like they are shedding water well
– I’m not adding much insulation. I see some of these projects much further north and with unpainted brick, adding R-20 or more to the inside of their walls and things are apparently fine.
– I’d guess that concrete “bricks” would absorb more water than fired clay bricks.
– The house is a Cape Cod style, with tiny roof projections.
Thanks for any opinions/ideas.
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