Built a new house in NJ last year under IRC for a family member. I believe the insulation sub put R38 in the ceilings and r21 on 2x6 walls if I remember right. The inspectors in my area were easy going with insulation. Didnt do blower test. Closed cell would have been better for heatloss/gain but was a good deal more and money was probably tight on that build.
Spray foam is awesome I did a house years ago all radiant heat 5000sq' with spray foam and condensing boilers. The guys energy Bill's are probably less than my old 800sq' shack of a house and way more comfortable.
Coming from an HVAC background I've got a few bones to pick with foam:
#1 makes house too tight/not enough air exchange from outside. Without a outdoor air exchanger you may have environmental issues/air quality. Which further adds to installation costs.
#2 makes it harder to run wires and pipes in the future. So planning ahead is key.
#3 most HVAC guys at least in my area way oversize equipment especially boilers. Better understanding of manual J and D with more experienced contractors should be used when system efficiency is important. Oversized equipment short cycles and is not good for comfort or longevity of the equipment.
I'm a master plumber by trade and we dont use ICC codes in Nj for plumbing. I do use the ICC fuel gas code though and I believe changes are usually highlighted with a line next to text in the code books.