Indiana CZ5 contractor here. Yes, 2 inch closed cell on rim joists is a Class II vapor retarder – you do not need poly there. My process: spray the sill plate and 6 inches of foundation wall first, then move up to the full rim joist. This creates a continuous air seal. Then lap the ground poly barrier up the foundation wall 6-8 inches and tape it. Perfect thermal and vapor bridge with no gaps. I have done it this way for 5 years with zero issues.
Indiana CZ5 contractor here. Yes, 2 inch closed cell on rim joists is a Class II vapor retarder – you do not need poly there. My process: spray the sill plate and 6 inches of foundation wall first, then move up to the full rim joist. This creates a continuous air seal. Then lap the ground poly barrier up the foundation wall 6-8 inches and tape it. Perfect thermal and vapor bridge with no gaps. I have done it this way for 5 years with zero issues.