Can you stack foil faced polyiso?
B3llo38
| Posted in Energy Efficiency and Durability on
Well my insulation plans have changed as I recently have access to a good amount of “recycled” polyiso 4x8x2 foil faced foam boards (both sides) that read r13. Also a good amount of 1.5x4x8 r9 foil both sides. Pretty much perfect condition from a warehouse project for next to nothing.
I need to insulate a vented vaulted ceiling in my home. Bays are 2×8 and about 16 foot in length. The 2x8s measure 7″. My plan was to do 1.5 air gap with blocking and install 5.5″ of these foam boards to fill the bay flush with the jousts where ill install drywall. So drywall will be touching back the 1.5 foil board. And foiled faced boards will be stacked as well obviously.
Will i have any issues with this set up in regards to moisture etc? I plan on cutting the boards to fit snuggly for a pressure fit so i wont need to foam the sides. Id worry about foam expanding and not allowing me to stack the boards perfectly as well. I will stagger the butt seams.
Do i NEED to fur out the bottom of the rafters for a thermal bridge? If I do that, how thick do I need and would it be okay to have a gap between the back of drywall and the foil insulation now because the furring.
My plan wasnt to fur out joists an just screw drywall directly to it and drywall would also be touching the insulation.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
Already answered here:
https://www.greenbuildingadvisor.com/question/can-i-stack-foil-faced-polyiso
It's probably best not to post the same questions under different sections of the forums.
Bill
Understood. I dont see an option to delete it