Foil faced rigid insulation
I am in mixed-humid (Zone 3A).
I plan to use foil faced roof sheathing in my vented attic as a radiant barrier and was wondering about the efficacy of foil faced rigid insulation on my exterior walls facing the air gap to the siding (brick, stone and plank). Given my climate, any wall moisture will typically dry to the interior, so it would seem the reduced permeability of the foil facing would not be an issue.
From inside out:
• Latex paint
• Dense pack cellulose or fiberglass (R-13 min) inside of 2×4 studs 16” on center (we could use 24” on center if code allows and we followed advanced framing techniques).
• Tyvek DrainWrap
• Foil Foam board (R-7 min) giving R-20 wall)
• 3/8 air gap
Wall variation, if it will be cheaper:
• Higher R-value in stud bays (R-15 or higher)
• Tyvek Thermawrap 5.0 in place of drain wrap and foam board.
• Total of R-20 or higher.