The stained glass window does a lot for this space. I'd love to have my glass-artist friend make me a piece! I'm not so sure about energy efficiency, but you'd be dancing whenever you saw this anyway (at least I would be) so it would all work out in the end. But really, if you want something like this and are concerned about energy, you can always place stained glass over an existing window. Easier than adding or replacing a window, right?