1. Placement. With a casement window, the entire one-piece sash rotates out by twisting a handle. It can be difficult to open a double-hung window when leaning over cabinets in a kitchen, so the casement can be a good choice there. Think about the exterior implications, though. Will the open sash obstruct a path when people walk by? Do you plan to have window boxes? You don't want the window to mow down your pansies.