I am building a house in Bloomington, Indiana, which is right on the line between 4A & 5A zones. I am wanting to add 2″ of rigid foam to the outside of the 2×4 walls, which will be filled with stabilized cellulose. What is the best method to attach the foam? Also, What is the best way to attach hardi-plank siding outside the foam?

One last question, is it still a good idea to add this 2″ of foam? My framer talked to my lumber supplier, and said they don’t have airnails long enough, so they want to go with 1″ foam. Will that hurt the cause?

Thanks!