I'm curious about the "fins", for a lack of a better word, that protrude out from the lower level windows. Do they have a purpose or simply decorative?
Yeah, I think they're both decorative and provide some shading on all that glass in the later afternoon (especially important in our summers).
I admire the street view of the building as seen when going west on P Street. The way some of the windows have brown fins rising off the glass, giving the exterior a texture and variation compared to the rest of the flat glass wrapped around the building. Thus far, the pedestrian plaza on the north side along O Street is a the least attractive view of the structure. Then there is the top of the building, the mechanical three story grey box on the roof that is only seen from the west, (the most photographed view of the skyline) a giant box that sticks out in a terrible way. If you observe the same tower from the Capitol looking west, the mechanical level is wrapped with glass to disguise what’s on top of the high-rise. The State also did this when building the EPA building on I Street in 1999, from the rail yards you can see the ugly mechanical roof but it you view the same building from the south or the Capitol, there is a nice glass wrap to hide all the stuff on the roof. You might get the idea that these offices are designed to have the most attractive side face the Capitol where the political wonks see the city skyline.