retrofit insulation in tight cavity

I’m retrofitting my new home with insulation. I’m having trouble trying to decide how to insulate the walls. The exterior walls are currently rock lath and plaster over 1 1/2″ furring attached to a block exterior. I’m considering either cellulose, or sray-foam, but i’m concerned that the material will have a hard time dispersing through the narrow cavities. I’m also not sure that adding the insulation would be cost-effective.
Replies
I doubt the ends justify the means.
Spheramid Enterprises Architectural Woodworks
"Success is not spontaneous combustion, you have to set yourself on Fire"
Maybe EIFS, with 2 inches of foam. Not cheap but maybe better than tearing apart your interior. Plus you get a new look.
In the 70's when I started the Builder I worked for built all his homes that way. Normally the inside block was light weight block that had some insulating properties.You have to realize that electric wires were crammed into these tight spaces and all electric boxes were shallow boxes. If I were you I would pull off the electric receptacle face plate and foam around the receptacle boxes. Additionally the floor joist were notched back and the plywood would be held back so a special size block could be laid between them. If you have access to the joist in the basement I would foam around each because a lot of air could easily enter there. Search Fine Home Building magazine they recently had an article about improving the insulation in this area by foaming. Window and door penetrations can be another area that by removing some casing you can foam and help a lot. Caulk the bottom of the baseboard on the exterior walls. Also utility penetrations need to be checked and foamed around. Finally depending on the plaster detail used the top of the wall in the attic may have a 1-1/2" opening around the whole permitter of the house. I would if accessible foam that space closed. I guess my theme here is draft stopping as opposed to actually trying to insulate that small space with wiring crammed into it. I don't think much insulation will flow past the wiring. If the home has forced air HVAC first use mastic and seal around the ducting that turners up into the heated space. Then foam between it and the exterior wall. Manny homes were built that way. My guess someone down the road will come up with a way to insulate that small space. I would draft stop know and keep my eyes and ears open for some new technique or material down the road. Hope this helps. Jay
I'm with Sphere. 1/2" of foam is what, R-2 or R-3? And go down from there for other options. Not worth the effort at this point.
Mike Hennessy
Pittsburgh, PA
1 1/2" closer to R7-R9, but I see what your saying
tigre foam or fomofoam has a pourable icynene foam for cavities like this
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"1 1/2""
DOH! On my screen, the "1" was separated from the "1/2" by a line break, so I just saw "1/2".
I was wonderin' why anybody would even think about blowing insualtion into a 1/2" cavity. ;-)
Mike HennessyPittsburgh, PA