Vapor barrier under polyiso on V-joint pine boards (and more)
I am moving forward with converting my timber frame barn into a home. North Connecticut zone 5.
I am planning on doing a build up roof of sandwiched foam polyiso and a layer of eps on top followed by a vent channel of 2x4s fastened down with headlock screws or such, then plywood and roofing. My question is , as I would be installing the layers of foam over the v joint pine what should I use for a air barrier? I imagine I could do a variable vapor product like intello. However as the rigid is impermeable to begin with could I simply go with regular plastic? If I stop the air flow ,it seems that the foam would be quite unlikely to take on moisture even during summer with ac. Am I missing something science wise?
Next I want to do some areas of the insulation on the walls as outboard Larsen type trusses , however in some areas( where it would be asthetically challenging) It makes more sense to do a combination of infill and outfill if you will so I would have 3.5 inches between the timber posts and 5.5″ outside the timbers . I will be insulating the walls with dense pack cellulose. ( I will need to Sheetrock then pack the inside and outside cavities, separately ) I am a bit hesitant with the putting interior vapor barrier fully inside as it would start and stop by taping to the timbers. So Can I just put the vapor barrier in between the stud walls , (3.5 inside air barrier 5.5 outside )being that it will be a perm variable product like intello, will the somewhat more outboard then ideal work for the location of the vapor retarder ?? Planning on doing a sheathingless wall with a layer of the proclima mento followed by rain screen and pine novelty siding. Any other ideas?
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