You have asked 3 questions now and haven't gotten a single answer, so I will try my hand at it.
I don't have IBC in my library but I have been told the bedroom windows have to be 36" wide and provide a certain square foot opening for escape.
Windows are always sized by the width first, so, if you have 24" wide windows a casement would not help anything. Some casement windows slide the pane over in the opening as they go out; you can stand inside and wash both sides of the window. That being said, those same casement windows will limit your space another 4 to 6 inches; no help at all.