By Craig DiLouie
The Chicago Board of Trade (CBOT), established in 1848, is a leading exchange in the United States. Originally, it traded futures on corn, wheat, and oats. In 2006, the exchange's volume exceeded 805 million contracts among 3,600 members trading 50 futures and options products.
In 1930, CBOT moved to its third and final permanent home, a 609-foot-tall art deco-era skyscraper at La Salle Street and Jackson Boulevard in downtown Chicago, which to this day remains a city landmark.
Several expansions and modernizations occurred over the years, but in 2004, CBOT decided to engage Austin AECOM and Harboe Architects to renovate and restore the building's key public spaces and features, including the exterior façade, main lobby, mezzanines, and some upper floor lobbies, to match the original design intent. The new space has impressed local architecture critics and received honors from Landmark Illinois and the Building Owners and Managers Association.
"After spending many years improving the infrastructure of the building over the aesthetics, we decided in 2004 to focus on bringing back the grandeur of the appearance of the building," says Kevin Lennon, CBOT vice president of real estate operations.
The Jackson Boulevard entry lobby, for example, had retained most of its original architecture. Restoration of the lobby involved cleaning marble walls and piers as well as the nickel silver crown molding and trim. In the east/west cross-corridor and elevator lobbies, the suspended ceiling was removed and the original plaster ceiling and crown molding restored.
The main arcade, the most dramatic of the lobby spaces, rises three stories and features a mix of various colored marble, nickel silver, and plaster ornament highlighted by a luminous ceiling that wraps down the north and south end walls. Surrounding this arcade are mezzanines on the second and third floors, designed as public spaces.
"The building, and particularly the lobby, is one of the best examples of art deco architecture in the world," says Lennon. "The main goal of the renovation was to bring the building back to its original luster."
Architecture critic Ed Keegan observed that the arcade space could be interpreted as a miniature version of the cityscape, acting as a sort of Main Street of a small town - a place where people congregate and communicate, including tenants and hundreds of visitors and tourists each day. It is also a thoroughfare for thousands of commuters passing through from one of the city's main train stations just to the south of the building.
Lighting Inspired by the Big Screen
The renovation coincided with the building's 75th anniversary and CBOT's transition from a member-owned organization to a public company. Lennon wanted the building to enhance the message it communicated about CBOT as an organization with a rich history that also embraces technology and change.
The lobby renovation resulted in significant lighting goals that prompted Lennon to approve bringing a lighting designer into the design team.
"Lighting was the one area that could make or break the project so we were not going to risk failure for what in overall terms is a relatively small cost," he explains.
Many of the original light fixtures had been replaced in the 1960s and '70s. The top priority was to attempt to reintroduce the original lighting while improving light levels and highlighting key architecture features. Specifically, the goals included:
- Restoring and recreating original decorative light fixtures.
- Renovating the luminous ceiling, a significant lighting feature.
- Illuminating the marble cascade features on the arcade side walls.
"One of the things that convinced me of the need for and the value of a renovation of the lobby was a few years ago we allowed a scene from the movie 'Ali' to be filmed in the lobby," says Lennon. "During the filming, the production company brought in large portable lights and flooded the entire space with light. Waiting for the filming to take place, I looked around and noticed details that I had not noticed in all the years that I have been in the building. At that moment, I was convinced we had to renovate the lobby and that the lighting would be the most important part of the job."
The resulting lighting inspired Chicago Tribune architecture critic Blair Kamin to observe: "Like a city whose lights have been turned back on after being knocked out after a summer storm, the arcade's visual power has been fully restored."
Robert Shook, IALD, LC, principal of Chicago-based lighting design firm Schuler Shook, describes his firm's design as a "stealth lighting design."
"We would be delighted if nobody realized that a lighting designer was involved," he says. "This was all about putting it back the way it was, but with a big boost from modern technology to increase light levels and save energy and maintenance costs."
Architecture in a New Light
Energy efficiency became a goal rather than an energy code restriction, as the Chicago energy code exempts historically significant buildings; the lobby had been recognized as historically significant by the Chicago Commission on Landmarks.
Integrating new energy-efficient light sources, such as linear and compact fluorescent lamps and ballasts, into the original fixture designs nonetheless presented significant challenges. The light fixtures and their new lamping had to work together perfectly and provide sufficient light levels. This involved light level calculations based on similarly sized standard fixtures that had IES photometric files available, then designing the fixture lamping based on similar lumen packages. The lighting designers also ensured that these sources did not result in "hot spot" imaging on the lenses.
"An interesting issue we had to deal with was there was no way to tell what the actual light levels were originally," says Lennon. "Preservationists always default to the position that everything should be exactly as it was originally, regardless of what the architect's desired effect would have been if newer technology were available at the time, particularly with respect to lighting as technology has evolved significantly since 1930."
For example, the design team discovered several sconces that had been added in 1940, presumably to increase illumination and highlight certain architectural features such as the cascading marble and plaster crown molding. "Based on this, the entire team, including our preservation architect, agreed that if the light levels produced as the end product may be slightly higher than originally existed, the architect's clear intent was to highlight these features, so we used modern lighting technology to achieve what the architect may not have been able to do at the time," Lennon adds.
Shook says his firm relied heavily on prototypes and mock-ups to demonstrate the effect of integrating new light sources into original light fixtures. The Landmarks Commission, fortunately, proved understanding about modern illumination requirements.
Restoration and Replication
Another aspect of the challenge was that the lighting designer could not add new lighting to the space to provide supplementary illumination, even if it was hidden from public view.
"We were restricted to using only the original fixtures and replicas of original fixtures," says Shook. "The only fixtures that were added were in the main entry lobby where the original design had one central fixture and four peripheral fixtures; we added four more peripheral fixtures to assure that the corners of this space were bright enough. In almost the entire space, however, we were fortunate that the original fixtures were designed and located in such a way as to allow us to rely on them solely for illumination."
Several of the original fixtures, however, had been replaced during the 1960s and '70s, requiring the design and manufacture of replicas for the project. "Less than half of the original fixtures were extant and could be restored," Shook says. The rest had to be recreated. "In most cases, we worked closely with the restoration architect to design replicas of the original fixtures based mostly on black-and-white photographs."
Lennon adds, "The fixtures themselves are true works of art with detailed nickel silver banding featuring inlays of corn and wheat representing the CBOT's importance in the trading of agricultural futures."
The Biggest Win
The final challenge involved renovating the luminous ceiling, a significant architectural and lighting feature. Historically, it had been lighted only from the edges, and the design team, examining photographs, concluded that it had never been evenly illuminated. The luminous ceiling was only 15 inches high, a severe restriction for distributing light. This is when Shook achieved his biggest win on the project.
"It was important to find a means to distribute the light within the luminous field," he says. "We installed T5 fluorescent striplights in continuous rows, oriented up, to illuminate the white reflecting surface above, and we included short side reflectors on both sides to prevent imaging from the lamps through the glass."
The glass, however, presented a further obstacle. According to Shook, the preservation architect preferred sand-blasted glass, which was true to the historic design, but mock-ups revealed sand-blasted glass to be not opaque enough to prevent lamp imaging on the upper ceiling. The final glass design, he says, was laminated glass with an opal white interlayer that worked optimally to reduce imaging while at the same time presenting a similar appearance as the original sand-blasted glass.
"The lobby looks better than it has in my years here, and I suspect that it looks as good or even better than it did when it was originally opened," says Lennon.
Concludes Shook, "It is very rare to have such care lavished on a project by the owner, and it was the primary reason why this project was so successful."
Craig DiLouie, a journalist, analyst, and consultant, is principal at ZING Communication Inc. (http://www.zinginc.com/).
