I was at a home remodeling show recently and I saw a foam insulation that is designed to go into the stud cavities of existing, finished walls. The contractor takes off some siding and drills holes in the exterior sheathing. Then they put the foam (low expanding foam) line in each stud cavity and fill it with foam. The existing fiberglass insulation is squished toward the back of the drywall and the foam goes towards the exterior sheathing.
I saw TOH put low expanding foam into the walls in the East Boston house where they left the plaster in place but I think those walls had no insulation in them to begin with.
Has anyone heard of this before or does anyone have it? What do you think of it?