Question for the group: I have just discovered a large window has been
leaking into the wall below. It is on it's way out and a new one will
be installed shortly, but I have to deal with the mess the leak left.
Fortunately it looks like the structure and outside sheathing will be
fine once it dries off, as I can detect no rot. I have the interior
wallboard off to get some air circulation into the space under the
window -- it was soaked on the inside, as was the old insulation, so
all that needed to be replaced anyway.

I'm thinking of taking on the repair of the wall myself. It's about 6
feet in length but only about a foot in height, between the floor and
the windowsill. I was wondering about using low-expanding urethane
spray foam insulation in cans to insulate the 4 approx. 18"x12"x4" bays
under the window. I have several of these cans on hand so I wouldn't
need to buy a package of fiberglass batts nor a sheet of vizclene as a
vapor barrier, so it would be cheaper. Since the wallboard is off, I'm
thinking I can shoot the stuff in, let it expand and cure, and if it
expands out too much, just trim it with a saw to be flush with the
studs. Am I crazy or will this work? I like the idea of sealing all the
little gaps with the foam. Any thoughts?