Hmm figured, so even if I pack it to the top with insulation right? If I go with the open concept ceiling, how does ventilation work in that case? Would I basically just build another slopped ceiling, then insulate that so there's a pocket of air between that, and outside?
Upon further research think I see how I'd have to do it:
Given the joists don't all meet at the center, I can't just cover them all with foam or something as some of the sections would not be ventilated, so I'll have to work around that, but I have a few ideas in mind. I'm thinking I could add small "blocks" of 2x2 pieces on the existing joists, but they would be spaced. I could then nail foam on them to create a 2nd ceiling space that meets with the wall. I would add a venmar vent at the peak of the roof. This would allow air to go through the overhang venting, between the rafters and foam insulation, and to the venmar vent.
I would then build another ceiling over the foam, and add fiberglass insulation, or I suppose I could just make it a flat ceiling and pack it with insulation then. Does this sound ok?