I just bought an 80+ year old row house in a Phoenixville, PA a Philadelphia suburb. The back wall of the house is a wall of the kitchen behind the stove. It is covered in wood paneling that is breaking down. When I pulled part of the paneling down, I found a series of 1 x 4 furring strips attached to the subwall. This subwall is plaster over wood lathe with various types of damage. In the worst spots, the old plaster is totally gone and there is only some loose fiberglass stuffed into the lathe, truly amazing fix I think. In other places the surface plaster is gone and only the scratch coat is left and it is cracked and loose. I am not sure how much of the wall is bad, bit I think it may be a large portion if not most of the wall. The outer wall appears to be wood as least as I can tell from the inside. The outer covering is some form of stucco. As far as I can see, there is no insulation within the wall cavity itself.
I am thinking of leaving the outer wall alone and having a contractor pull down the inner wall to the studs and rebuild. With the wall open, it will be easy to put in any type of insulation.
The cavity is about 5 inches deep and I am considering some form of expanding foam. Any thoughts or comments?
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You will definitely get the best results by stripping down to the studs, insulating, and drywalling with new drywall. Your plan is a good one.
It may be worthwhile to sister new studs onto the old ones to increase the depth of the wall and provide a flat plane for the new drywall. If the old studs don't form a flat plane your carpenter would be futzing around to shim it flat anyway. When sistering the studs you can gain a little extra thickness in the wall cavity that would allow more insulation.
"Sistering", by the way is attaching a new board side to side to an old one, with the new one often sticking out past the old one. It's a common method to create a flat plane when remodeling old structures.
As for insulation, everyone has an opinion, and there are some knowledgeable people here, but the simple fact is that anything modern you install that is installed properly will be fine. If you were going to do a whole house you might try to optimize, but you might find out for a job as small as yours that the more advanced insulations may be too expensive for your budget.
You absolutely need a vapor barrier on the inside of the insulation unless you go with one of the few that acts as a barrier itself.
I hate to say this but there is a good chance the old paint contains lead. Proper precautions are necessary.
Sistering is probably a good idea. The paneling is probably not too old and is coming down in chunks so I am not too concerned about lead paint there. Under that, it is all wallpaper as far as I can tell, but I will be careful.