Double Stud Wall Green?

sawyerEd

gregJ I don't think anyone said that thicker walls can't have condensation problems. There will be a dewpoint somewhere but in a super insulated wall you need to reduce the amount of vapor that is driven through the wall in the first place. Critter is right about drywall being an effective vapor retardant layer, unfortunately it provides an excellant medium for the growth of toxic mold if moisture gets to it. Nevertheless it is still being installed next to 6mil poly in basements everywhere, risky or stupid? You pick.

mmcgolly

I just finished an American Foursquare with advanced framing (under rain screen walls) in an effort to increase insulation and decrease thermal bridging. By the time the engineer got done with it I had four walls with so many studs around windows that I might have actually increased thermal bridging in a place I really didn't want to. Combined with the challenges of attaching the exterior cladding and trim, interior rock, trim, etc.....well, I'm not using that again. I'm planning all my new construction - and remodels where possible - around double stud walls, probably on 2x8 plates and 16" centers. The studs don't have to be offset since they will have a 1/2 gap between the inside and outside. Any required firestopping should be minimal but it may be challenging to convince my local inspectors. My education (BS Urban Ecology, MS Resource Management) and the latest Life Cycle Analyses tell me to use more wood. I never use cementitious exterior cladding and no steel, except for reinforcing and roofing.

Michael McAuley - Bellingham, WA