Spray foam in attic
I have read and read on spray foam. some good, some bad. I know that the chemical mix is the most important thing. that being said,
if it were me, I would want the fiberglass etc removed, the area cleaned and the upper side of the ceiling foamed, not the roof plywood etc.
I dont like the idea of a conditioned attic with no ventilation. I dont like the added expense and more foam and more weight on my roof (I have tile already, which is heavy) also roof repairs would be harder.
with it on the upper side of the ceiling, there would be less foam used, less weight used and gravity would not be trying to pull it loose. also, this way it seals the ceiling from air leaks.
just my thoughts based on my reading and opinions...