We have a stained glass window that is single pane and closes with about a 2 mm space between it and the opening. It makes the room (my 2 year olds) about 6 degrees colder Han the rest of the house. She's either freezing or we are sweating. I've already tried that plastic film stuff meant to add a second pane...useless. We dint want to seal it completely. What can we do that is kind of temporary but will actually keep the cold out? Thanks