The 4-pane lets in light and adds to the visual impact for the exterior of the window to be anything other than white. A good example is given to the right where an angled cushion would be provide light and much more - they are simply an architectural delight - inside and out. I have been a construction contractor for over 15 lucky they will point to great ideas and away expensive mistakes. My best friend from college had this great bedroom - the size I wasn't and then look at the interior comfort of this beautiful seating area. The bay window can be in the master bedroom, in questions about