On 2005-10-24, No wrote:

I would just leave the bats and add tyvek and, if your remodel would
allow for it, insulated foam board to the outside.

Well, I fall on the felt side of the tyvek vs felt argument, so I'll
be using 30 lb felt. The siding is cedar shingles, and at least some
cedar shingle manufacturers recommend felt instead of tyvek. I may
use cedar breather (1/4" thick mesh) under the shingles as a mini rain
screen.

As to the foam board, is there any value to 1/4" foam board? Would it
be an effective air barrier, and what would I use to tape the seams?

I don't want to make the wall any thicker than it is, as I don't want
to mess with the frieze board and molding details at the top of the
wall. So I'll be leaving 2-3' of the 7/8" plank sheathing at the top
of the wall, and there I'll just have to seal the gaps in the
sheathing with spray foam.

But the new sheathing will be 1/2" or 3/8" CDX, and I'll have 3/8" or
1/2" of thickness to make up. So I could use 1/4" foam board and 1/4"
cedar breather.

Cheers, Wayne