watching the snow fall outside my office windows, I was reminded that I took a number of photos on a recent trip to Chicago of the classic 'Chicago window'.

To maximize light into the building, prior to the ubiquity of fluorescent lighting, these large windows account for more than 50% of the wall surface. The classic Chicago window is an A-B-A rhythm that allows the smaller side window to open and the center picture window to be free from mullions. Obviously this is also before the days of hermetically sealed HVAC systems that eventually made the whole exterior a curtain wall out of glass but none of it operable. I don't know if the center window's width was maximized up to the maximum size of available glass or not, but the bay size of the overall window almost always corresponded to an evenly parceled out division of interior space.

Now in the days of LEED certification and green and sustainable construction, maximizing exterior lighting, with appropriate controls, has once again become standard as has individual office control of operable windows. Maybe all those storied firms of Chicago's architectural heyday had it right.

Thanks to Burnham and Root, William Le Baron Jenney, Louis Sullivan, Holabird and Roche, and Shepley, Rutan and Coolidge