[Greenbuilding] exterior wall sheating/insulation

[Stewart Abbey]

I am building a passive solar house this summer near Montreal.  I would like advice
on exterior wall insulation for best performance.  I am planning a 6 inch wall and 
insulating with 6 inches of Roxul (rockwool) R-22. I believe the performance to be better than fiberglass.   Is there an exterior sheeting that could take the place of plywood or osb and give some insulation at the same time. (like styrofoam but
with some structural properties. Otherwise I'm thinking of 1 inch of polystyrene to give a thermal break.  Also what about below grade exterior basement wall insulation? Roxul has a sheet insulation approved for below grade, anyone recommend it?
Thank-you
Stewart

 		
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