Insulating the foundation of a building is important in order to prevent the concrete from acting as a thermal bridge. Othen this is done by applying foam board to the outside of the foundation's concrete walls. With a curved foundation wall I was curious how this might work. Yesterday I did a little test. I scored one side of a piece of 2" foam board and was then able to bend it without a problem. This should work very well with my foundation wall, which consists of short curves and longer straight runs.