I am in the process of residing my house with western red cadar siding, and think of adding some additional
insulation on the exterior of the house..
I am thinking of placing a 2″ layer of Polyisocyanurate (foil faced) foam panels on top of the sheathing before
reinstalling the siding, The only question I have is the foil facing – should it be placed against the sheathing
or placed facing the finish siding, or eliminated altogether?
I would appreciate any and suggestions for you regarding the correct approach.
Thanks,
Jim
Replies
Foil faced
Foil faces foam board should have the foil facing out.
Are you using a house wrap or felt paper over the sheathin before to install the foam or is it already there?
What about an interior vapor barrier? If you have a vp on the inside of the walls, you could be creating a double vp that traps moisture inside the walls.
Since you are residing I assume you are going to use furring strips over the foam board to attach the siding. Look up Rain screen walls for how to construct and detail it. You need to use foil tape over the foam board joints to achiev both a water tight drainage plane behind the siding and make a toght exterior vp.
Foam board
Thanks Dave,
The housewrap is already there (TYPAR); the only inside vapor barrier is the kraft paper on the insulation,
which faces the interior of the house. I will check out rainscreen walls as well.
I guess my only question is the foil on the foam board - no foil, or, if foil, which way should
the foil side be faced?
Thanks for any input!
Jim