I'm a carpenter here in Asheville,NC zone 4/5 and trying to design a home for myself so I need to make it as inexpensive and green as possible. I'm thinking of a shed roof using flat trusses with blown cellulose to R-60 and a metal roof. Of coarse, there will be eave and "ridge" vents. So do I need to sheath the roof for metal or will just using purl-ins work. My main concern in condensation. If you dont think this would work could you suggest other systems that would be inexpensive labor is less an issue since I will be doing most of the work myself.