The Reason Isolated Wings Exist

I recently discussed the wind-bracing of slender wings on high-rise office buildings. Given that these wings were difficult to build, made parts of the buildings sort of funny-looking, and were more expensive than solid blocks of buildings, why do they exist? Why were they built at all?

The picture above is (again) the view out of my office window. We’re looking at a fairly ordinary 1920s high-rise office. But you can see the reason for the slender wings. Here’s a close-up:

We’re looking in through window, across the width of a wing, and out another window. This building actually has a U plan, so if everything were lined up properly, we could look though four windows in two wings and out the far side.

Narrow wings – or inversely, courts cut into the volume of a building – provide a way to get windows closer to the center of the area. In the age before mechanical ventilation and air conditioning, it was necessary to use windows to keep the interior of buildings from becoming dangerously hot in the summer. In the era of early inefficient incandescent bulbs, having natural light from windows was useful, if not critical. Pre-WWII buildings with large uninterrupted floors tend to be buildings where there wasn’t a lot of reading going on and where people didn’t stay in one spot for long periods of time: stores, train stations, factories, and warehouses for example. On the other hand, offices, hotels, and apartments tended to fall into two categories: small enough so that windows were naturally close by all of the interior, or provided with courts to break up the interior into wings. In New York, the courts tended to be on the outside; in Chicago, there are a number of buildings where the courts were interior atriums. For example, here’s the third floor of the Rookery, where the skylight over the lobby sits at the base of the light court at the center of the square-donut floor plan: