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Building in Nebraska (Zone 5). Builder proposed 2x6, 1/2" spray, then fiberglass batts.
I understand 1/2" sprayfoam would raise condensation issues. In meeting with the builder soon, I will propose three alternatives:
-2x6 wall but 2" sprayfoam, then fiberglass batts/blown fiberglass/cellulose, depending on price and availability.
-2x6 wall and 2" rigid foamboard on exterior, then fiberglass batts/blown fiberglass/cellulose (my builder has not done this before and may not be comfortable with this)
-Double stud 2x4 walls with fiberglass batts/blown fiberglass/cellulose, just as shown at buildingscience.com  (I doubt he has done these either, but this involve less of a learning curve?)
I realize the two latter options are clearly better than the first, but ultimately I'm limited by what builders around here are capable of and willing to do. Do these three options sound good? Am I safe using 2" of sprayfoam in the first option? Also, if we do double stud, I'm confused as to the best way to reduce the risk of condensation. Any thoughts would be greatly appreciated.