Are you doing this repair from the inside? If so, I did exactly what you
are proposing. The only difference is that I put a good size bead of
caulking on all four seams of the space and smushed the poly board into it.

A more recent example is to cut the foam a bit smaller then the opening
leaving say about a half inch gap all around and then going back with the
spray foam to fill in the voids. Much easier then trying to get tight fits
with the foam board.

"blueman" wrote in message
...
"Lawrence" writes:
On Jan 29, 3:44 pm, blueman3333 wrote:
We seem to be having a fair bit of cold penetration along the basement
mudsill (above the stone foundation) and between the floor joists.

I would like to insulate and my first thought is to use a combination
of the 2 inch "pink" rigid insulation (cut to size) plus expanding
foam insulation to fill remaining irregular gaps.

Any other or better suggestions before I start the project?

The ideas you have sound OK. Since the draft is coming in through the
floor jouist I would consider getting up there with come regular caulk
and seal all the cracks where the cold can come in. Foam is only
needed for really big cracks.

At that point you could just use fiberglass bats which are
conveniently sized to fit in the space between the joists. It would
require some type of ceiling to finish however, drywall perhaps. A
finished basment adds to the function and value of the home and
finishing the ceiling is a big step in that direction.

Perhaps my explanation is unclear. The area of cold is along the
outside *perimeter* of the house at the level of the "mudsill" which
in my old house is something like a 4x10 or so resting (irregularly)
on top of a 12 inch or more stone foundation. My guess is that a lot
of the air is leaking between the inevitable cracks between the
irregular foundation and the mudsill. But additional cold is probably
penetrating the mudsill itself since wood has a rather poor R-value.

So I was proposing to cut (irregular) rectangles of 2" pink rigid
insulation to fit between the joists along the perimeter mudsill. Then
since everything is rather irregular anyway I was going to use foam to
seal between the rigid foam and the surrounding joists, stone
foundation and mudsill.

Does this explanation help?