Council on Tall Buildings and Urban Habitat
CTBUH Willis Tower Tour

October 29, 2009

On the occasion of saying goodbye to our Development Coordinator, Katharina Holzapfel, the CTBUH staff had a unique opportunity to see the in and outs of the Willis Tower in Chicago, from the very top to the deepest bottom.

Skydeck and The Ledge
Guided by a very knowledgeable representative from the American Landmark Properties, the Skokie based managing corporation of the Willis Tower, the first part of the tour took us straight to the 103rd floor. This is the level of the Skydeck observatory, which since last summer has a spectacular new attraction called The Ledge. Devised and executed in just a few months, the four glass cubicles offer a spectacular view of the Chicago area to the west of the Willis tower; including an unobstructed view straight down to South Wacker Drive! 

South Wacker Drive
In The Ledge

Skidmore, Owings and Merrill, the architecture firm that designed the tower, also designed The Ledge. The four 1-1/2-inch-thick glass boxes extend 4.3 feet out from the side of the building at 1,353 feet above street level. The boxes are capable of holding up to five tons of live weight, which is twice the required amount to allay fears that too many or too hefty individuals might cause the unthinkable. The boxes are retractable to allow window cleaners to pass, an event that happens approximately four times a year. The inspiration for The Ledge came from hundreds of forehead prints visitors left behind on Skydeck windows every week.

Fixtures at the top...
...and the bottom of The Ledge.

After a few spectacular moments we were allowed to climb even higher. After ascending seven more levels and a tour of the installation levels, we reached the roof of the Willis Tower. For a few moments, being at 1450 feet, the CTBUH staff was the highest group of people standing on a building in the United States. It also allowed us to take a close look at the massive antennas and the other systems on the roof of the tower.

Antenna Antony handing over a certificate of appreciation to Katharina

The rooftop of the Willis Tower will play a substantial role in the $350 million retrofit which was announced last summer, which aims to reduce its energy use by 80 percent of base building energy. One of the most basic yet beneficial improvements is reglazing the building’s 16,000 single-pane windows. This creates effective daylighting and ultimately 40 percent less lighting energy consumption. This is a big move away from the original heat-by-light system, whereby lighting fixture heat was trapped and piped through ducts to warm the building’s rooms. When the outdated HVAC, elevator, and plumbing systems are replaced, they will operate as much as fifty percent more efficiently. The new plan also integrates wind turbines, which, along with solar hot water panels and green roofs, are being tested to withstand high-altitude wind conditions on the tower’s set-back rooftops.

From top to bottom: Antony Wood looking up.

Katharina Holzapfel and Steve Henry testing The Ledge test

. the deepest level of the Willis Tower

From the rooftop we went straight down to the four subterranean levels of the tower, which are mainly occupied by installations. The size of these levels makes one realize how much hidden infrastructure is needed to run a building the size of the Willis Tower. A visit to one a typical office floor concluded our tour of the Willis Tower. This particular floor’s open plan revealed to us the enormity of the space the Willis Tower has to offer.

Cleaning installation in the top of the tower. Water installations in the basement levels.

We would like to thank American Landmark Properties for their hospitality, which enabled a spectacular good bye to Katharina Holzapfel. Although she has relocated to Germany after having been part of the full-time Chicago staff for over a year, she will continue to participate as a contributory staff member, becoming our News Editor.

CTBUH staff in The Ledge: Marshall Gerometta, Patti Thurmond, Katharina Holzapfel, Antony Wood, Jan Klerks, Nathaniel Hollister, Steve Henry and Matthew Lacey.