I bit the bullet and put in closed cell foam on the underside of my roofdeck and attic walls in order to bring the attic into the house envelope (air handler and ducting were already in the attic). Climate zone 5a.

There are two old single pane gable windows without storms and I am wondering what I should do with them. Plexiglass caulked in on the interior to create an air barrier? Should I just cover them with insulation and if so what kind? I know there are lots of guides out there to improving window insulation but given that these are in the attic and I don’t really need to have the window functionality wondering what the best path is. 

Thanks!