Greetings, Im currently renovating a 100 yr old rowhome end unit and adding a large framed addition that will have a flat roof deck surface that will be coated with FRP over OSB ;2×12 joists( no venting /warm roof) -there are so many controversial articles on how to properly insulate to avoid moisture entrapment it is dizzying..

I have read closed cell PU foam has failure issues with moisture entrapment and when applied thicker (r50 ) it has a higher rate of offgassing problems. Is this common? would I be better to use a thinner application of foam and remainder of batt insulation ?spray underside of osb directly or (idea) apply vapor barrier to underside?

and yet another concern in the insulating process, the old brick exterior walls, should I spray insulate-the wall is not in the best condition and I feel the spray foam will contain the failing brick and help support ? there are some debates of close cell actually causing more damage than helping due to moisture containment and capillary action from footer?. and is it recommended to leave an open unsealed parged area exterior at ground level to relieve the moisture , will that actually work?

thanks for any replies .