I'm trying to figure out how to deal with a small section of roof that extends off a 12-12 gable roof section. It used to be a porch and has 2x6 rafters. I would fur out the rafters to add room for insulating and venting but 1. The low point of ceiling is already only 73" and 2. Clearance to edge of the window is only a few inches beyond rafters edge. Should I look into closed cell spray foam and keep this roof unvented as highest R value I can pack in? Previously, it was not vented and had r13 insulation. I'm in south/central Indiana.