I am having the house resided but wont be able to add a full 2 inches of foam board due to current window planes. I do have some walls that dont have any windows, so it should be a problem from that perspective. I live in New England by the way.

Would there be any concerns with adding 2 inches of foam on the window-less walls, but not the abutting walls? I know the foam will be vapor impermeable, and wonder if there should be special consideration for the ‘edge condition’ where you have 2 inches of foam, meeting 3/8″ perforated fanfold and tyvek.

Not sure if its just the windows and roof plane that caused my contractor to say he cant do the full 2inch, or something i am missing on that. I said if we cant do 2 inches, id rather skip and avoid moisture build up in the cavity as described in some building science articles i read.

Thanks