Boarding up basement window from the inside with foam
I don’t need our 4 basement windows and would like to cover them up from the inside with 2″ of Thermax polyiso, and seal the perimeter with canned spray foam, so that absolutely no interior air would get in contact with the windows. I just finished insulating the rim joists with the cut-and-cobble approach presented on this site, which got me thinking about using a similar method for the windows. Is this a viable approach, or will the wooden windows rot out in no time?
In his reply to another post, Martin suggests bricking up unwanted basement windows, but I don’t feel as confident with a trowel as I do with a foam gun and glue. There is also lead paint that I don’t want to worry about. I like that the process of installing foam in this way would be potentially reversible.
Details: Climate zone 5, 100 year old unconditioned basement with cinder block walls. No apparent mud sill seal. Windows are wooden single pane with storm. They start about 8″ above grade, up to the sill plate at 2′. They currently don’t show signs of rot.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part