I built a similar sized home using ICF foundation 3 years ago in upstate NY. It was about 1/3 more costly than a conventional poured concrete foundation. The savings for me was in heating costs. The basement is a constant 50 degrees most of the year even with 25 below zero temp outside. If I were to do it over again and I could afford it I would have used the ICF all the way up for the second floor.
Best of luck with your project.
