Spray foam inside with foam board outside?
I have a wood structured home with fiberglass insulation in each bay, OSB sheathing, a 1” layer of foam board (on all areas that have siding on them, but not under brick facade), a house wrap (also only in sided areas), and a mix of cement board siding and brick facade. Home was originally built in the 1970s and was resided this year.
My question is, as I refinish interior rooms, what is and isn’t safe to do in terms of insulation? Can I tear it down to the studs, pull out the fiberglass, spray foam ~1” thick to seal and reinstall the fiberglass? Is it safe to sandwich the OSB between foam board and a vapor barrier on one side and spray foam on the other side? Is it safe to spray foam behind brick facade? Do I just need to get open-cell foam to avoid moisture issues or can I use closed-cell? Would open-cell still air seal?
The base fiberglass is only R11 and my exterior walls are only 4” studs. I’d really like to achieve a passive house standard – at least in terms of total energy use per square foot. So any advice on how to insulate best (recalling that we already dumped money into an exterior remodel) from here would be greatly appreciated. I am concerned if I do it wrong I could cause mold issues and would prefer to avoid this.
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