working on the final details of my plan and am debating the best way to insulate/vent part of my roof. Zone 6. It is a single sloped shed roof to be built with 14" ijoist 24" centers. It forms a clerestory area. Both ends are open and can be vented. Below the windows sloping away and down is also a single slope shed roof. However the lower roof, since it dies into the clerestory wall, does not have the option of being vented. Here are the few options I am considering. High roof (approximately 600 sqft)- install 2" XPS to underside of upper flange, foam joints, net and fill with cellulose below. Option 2- fill joist with open cell foam, do not vent. adds about $700, but saves time of installing the vent Option 3- fill the entire 14" with blown fiberglass or cellulose. Does not appear to meet code requirements for impermiable insulation, however I see them doing it often on super insulated structures at Green Building advisor... Lower roof- unvented, about 400 sqft option 1- install 2 or 3 layers of 2" xps, fill remainer with batts or blown insulation. option 2- fill with open cell foam (adds about $500 over above option) Option 3 is the same as above, blow the entire thing full. I am tempted to just foam both roofs to keep them tighter. only looking at just over 1k add in cost, so not huge, but every 1k adds up here and there. The rest of the roof areas are trussed and will be r60+ of blown insulation. thoughts?