We are going to be building a new home in Springfield, IL. I want to use 2x4 construction with spray foam insulation. I have read the need for a 1" foam exterior sheathing. Is that still needed (or recommended) if I use spray foam as my insulation? Just as a note I do want to use ICF's as my insulation for my basement walls. In addition, I am looking into a vent-free attic space. Any thoughts?