Great feedback, thanks!

The ceiling would be pretty easy to insulate and add a vapor barrier to. The frame uses English tying joints with floor joists that set into the tie beams; I left a space of about 3 or 4 inches between the outermost joists and the roof plane, so it would be easy enough to have the second floor's insulation wrap down over the outer joists and tuck into the wall space, helping to seal that off.

As far as what to use for ceiling insulation, I'm still undecided. The second floor framing uses 4x6 joists on 2' centers, so I was considering covering that with either rough sawn pine or OSB, then a vapor barrier, and then using either foam panels or fiberglass, topped with OSB. There would be an insulated trapdoor at the top of the access stairs, and the space would only be used for storage. What are your thoughts on this, would one way be better than another?

As to the walls, I should be able to use a continuous layer of foam panel on the outside of the eave walls, then strap and side them easily enough, using foam infill on the interior as well. Even without using foam on the outside of the gable ends, I'm guessing it would make sense to strap before siding anyway, to allow an air space? I might be able to use 1" foam panel on the exterior of the gable ends (up to the tie), then add studding above that to the roof. It would minimize the overhang, but I'm OK with that, my house was built in 1790 and has hardly any overhang, so it would match, I guess. As long as I include an airspace to let the walls dry out, I'd still be OK without a vapor barrier?

Vapor does indeed start to get complicated, ack.

Audi