Markus, MTUs ETEC team leader, is plugging unused basement windows with foam board. Usually it is put up on the inside of the basement, but in this case the sill is on the outside. Matt is happy to have them up and doesn't mind the aesthetic. After they are measured and fit snugly in, they are spray-foamed around the edges.

In a window that is open in the summer, one can size them snugly, don't spray foam, and pull them in and out seasonally.