Foam board to fill window opening
renogrant
| Posted in Green Building Techniques on
I am renovating my kitchen and removing a window. The current sheathing is wood panels. I was considering putting rigid foam board (likely polyiso) in the window’s rough opening to act as the sheathing. I will then put denim insulation in the cavity, covered by drywall. Does anyone see a problem with this setup? Particularly can the foam board act as sheathing in this small section of the wall? Thanks!
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Replies
Depending on what you’re using for siding, you’ll probably want to put something with some structure to it in the opening like plywood or OSB. There is no reason not to also put some polyiso in though, it’s just that polyiso alone won’t provide any strength to the wall or anything to fasten siding to.
Bill
renogrant,
Can you clarify why you want to include the foam there? Sheathing is usually confined to the exterior of walls. The rough opening is uncovered dimension lumber.
Thanks. The poly would act as the sheathing on the exterior of the wall. The wood siding would be nailed through the poly to the wood structure. I believe the value in using the foam is that it would limit thermal bridging and provide greater r value.
Thanks. The poly would act as the sheathing on the exterior of the wall. The wood siding would be nailed through the poly to the wood structure. I believe the value in using the foam is that it would limit thermal bridging and provide greater r value.
Then that would work. In my own home, I have T111 siding over 1/2” polyiso, with the T111 nailed through the polyiso directly into the framing.
BTW, using “poly” when you mean “polyiso” will cause a lot of confusion with construction people. “Poly” usually means “polyethylene”, which is commonly used as a vapor barrier. “Polyiso” means “polyisocyanurate”, which is a rigid foam insulation product. A very big difference! :-)
Bill