Two. Across from each other for cross ventilation.
Cutting a hole and putting Plexiglas across it, you might have leakage problems. You've got to be careful about water because it will rot the wood around the window. It can be done, but needs some careful planning.
Cutting a hole and putting Plexiglas across it, you might have leakage problems. You've got to be careful about water because it will rot the wood around the window. It can be done, but needs some careful planning.