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The Willis Tower

2010 August 25
by Caroline Nye Stevens


CNS 2010

233 S. Wacker Drive

The Willis Tower has been making headlines for decades. For 23 years it held the record for the world’s tallest building, and its height continues to be unparalleled in the Western Hemisphere*. The tower was the source of public outrage when there was talk of painting it silver (that’s never going to happen), and again when there was talk of changing its name from the Sears Tower to the Willis Tower (that did happen). Most recently it has become a key subject of Chicago’s effort towards sustainable building practices. Silver? Everyone agrees that it would look best in green.

Completed in 1973 and designed by Skidmore Owings and Merrill (SOM), The Willis Tower stands 1450ft tall (1729ft including antennas) and contains 110 stories. It held the record as the world’s tallest building until the Petronas Towers in Kuala Lumpur were completed in 1997. How did it get to be so tall? For that we can thank SOM engineer Fazlur Kahn. What Kahn developed is called a bundled tube structure. He divided the building into nine separate towers (each 75ft square) making the floor plan look somewhat like a tic-tac-toe board. Bundling or banding these sections together gives the building a great deal of stability. Kahn’s partner in designing the tower was SOM architect Bruce Graham who conceived of the idea to have the towers cut off at varying heights. Two towers terminate on the 50th floor, two more on the 66th, and three remaining towers on the 90th, thus leaving only two towers to rise to the full 110 stories. Supposedly, Graham’s inspiration for the design came from opening a fresh pack of Lucky Strikes cigarettes. Wherever his inspiration came from, the tower’s setbacks serve far more than just an aesthetic purpose.

Most significantly, the setbacks help to dissipate the pressure of wind against the building – an important quality, considering the tower’s tendency to sway back and forth up to six inches from its center. The setbacks also serve an economical purpose. The Sears Roebuck and Company built the tower with the intention of consolidating all of their seven locations into one central building. The company occupied the lower fifty floors and rented out the more enticing and expensive upper floors to help cover the cost of the $186 million project.

When built, the Willis Tower featured many smart innovations, but sustainable design was not among them. In a single day, the tower consumes more energy than a city of 152,000 people. Hopefully this is about to change. The tower’s current owners (Sears moved to the Hoffman estates in 1993) are working with the local architectural firm of Adrian Smith + Gordon Gill to renovate the Willis Tower into a sustainable, green building through a variety of measures such as: replacing and glazing the windows to cut down on heating costs, upgrading restroom water fixtures, investing in water efficient landscaping, installing automatic light sensors, and experimenting with wind turbines, solar panels and green roofs. This is a big deal considering the building is large enough to have its own zip code. In sum, the renovation would cut “base building” electricity by 80%, which is the equivalent of 68 million kilowatt hours or 150,000 barrels of oil saved per year. Adrian Smith and Gordon Gill have also designed plans for a connected five star hotel that would draw net zero energy from the power grid. If the hotel is built, the Willis Tower will make headlines yet again.

* UPDATEIn November of 2013, the Willis Tower lost the distinction of being the tallest building in the United States to One World Trade Center in NYC. Read all about it here.

CNS 2010


To learn more about the history of the Willis Tower or if you are looking for visitor information, visit the Skydeck’s website. And for more detailed information on the greening of the Willis Tower visit Adrian Smith + Gordon Gill’s website. Click here to read Blair Kamin’s biography of Bruce Graham who died earlier this year.

To the left: the focal point of the Willis Tower lobby — Alexander Calder’s mobile, the Universe.