The perimeter concrete walls received a 2-inch coating of closed cell spray foam insulation by folks from The Green Cocoon out of Salisbury, MA, who did an excellent job of spray installation and clean up. There's a reason why that insulation is colored light green. My Iowa farm roots beat loud and proud when I learned that the spray foam insulation was made from soybeans! Not only is the insulation made from sustainable materials, but it contains no VOCs, HFCs, or CFCs. I will admit that it was still a smelly process while they were working (we abandoned ship for the local shopping mall), but a quick airing out of the house for about 30 minutes and the odor was gone.