2 x 8 Wall Construction questions – GreenBuildingAdvisor

I’m building a house next year – single-story 2300 sqft ranch in Zone 6 (Maine), and want to use 2 x 8 wall construction, 24″ O.C., R-30 Roxul, sheathed with 7/16″ OSB, a WRB, and D4 vinyl siding for cladding. The last new house I built was in the mid 1990’s, and I’m doing my best to come up to speed with the current building science and methods.

I’m looking for advisement on moisture control for my walls, I’m assuming that I will have some type vapor barrier or retarder facing my inside surface of my wall studs and ceiling truss bottom chords (R-60 blown in celulose in the attic).   Do I need a smart vapor retarder? Any preferred brands? Is 6 mil poly out of the quesiton?

Also, any advice on a good WRB?

Thanks-