I'm not sure about foam insulation on the walls, but I know from experience that you need some type of barrier on the ceiling of a pole barn to retard sweating. I have two barns, both about 40 x 60, one with one inch foam pads under the sheet metal and one with nothing under the roof metal. The one without anything under the roof drips internal moisture continually during certain times of the year. At times it almost appears that it is raining inside.
