I live in east Texas and have a tiny home shell with wood 4x8 sheet siding. I want to put viny siding on. For insulation foam sheets on exterior can I use formular 1/2" or does the foam sheet need to be foil faced? And can i also use 1/2" formular between the studs on the interior along with my fiberglass insulation? Would I need to peel off a little bit of the fiberglass so it doesn't smash against the formular or not?