Howdy Ya'll- My first post on the internets' best forum... First- The Situation: I just purchased an old house (originally coal miners' quarters owned by "The Company" built around 1900). I've taken most of the house down to studs. It was framed with true 2x4's and 1x12's running vertically from foundation to roof along the exterior. Currently (traveling from interior to exterior) there is 1x12, tarpaper, 3-tab roof shingles used as siding then vinyl-siding. I plan to add 2x2 furring strips (making a 5 1/2" wall cavity) to thicken the exterior walls so I can increase the insulation. second, The Plan: My idea was to put 2" of foam board in the wall cavity and fill around the edges with 'Great Stuff'. Then add 3 1/2" Roxul (mineral wool batts) to fill the cavity and bring me up to r-25 in the walls. Finally The Questions: Should I add a vapor barrier (tyvek?), an air barrier (plastic?) or nothing along the interior before sheetrock? Should I install the insulation the other way around(mineral wool towards the exterior and foam board along the interior)? Man oh man i want it to be perfect. Oh, and I'm in West Virginia at over 3000 feet. Thanks a bunch Ya'll!