Discovered that the walls are not insulated, and that the drywall ceiling simply rests on the walls and is nailed to the joists above. Plan is to insulate walls, but will need to frame them out, and to add insulation to the attic (currently rodent-invested blown in fiberglass). Ceiling above ugly drop ceiling is in bad shape. My thought is to expose the joists and stain them for a decorative look since I have to put the work into taking the ceiling down anyway. But I'm not sure if it's ok to put insulation on top of the plywood. Thoughts?