june 10 | Metropolis

Skyline: Willis Tower (excerpt)

by Belinda Lanks

An ambitious plan to green the former Sears Tower includes a zero-energy hotel.

Chicago, the birthplace of the skyscraper, my soon see its most recognizable landmark get a green retrofit. An ambitious planned renovation of Willis Tower (formerly and better known as the Sears Tower) will cut energy consumption by about 40 to 45 percent.

Completed in 1973 and designed just before the energy crisis, the building (the tallest in the Western Hemisphere) was a testament to engineering prowess, not energy efficiency. Since then, as tenants, including Sears, moved out, various owners have made gradual energy-saving improvements, upgrading light fixtures and changing the air-handling system to reduce its energy consumption by about 35 percent. In its bid for LEED certification, the building's current management, U.S. Equities, has introduced electronic recycling, bike sharing, and discounted parking for alternative-fuel vehicles. But in its grandest gesture to date, it has hired the Chicago firm Adrian Smith + Gordon Gill Architecture to produce a wide-ranging program to improve energy efficiency and design a neighboring, net-zero-energy hotel.

The first step in modernizing the tower is upgrading its 70s-era facade, which leaks cold air in the summer, and warm in the winter. In addition to replacing the 16,00 single-pan windows with double-pane, insulated ones, the Smith + Gill team is considering placing a second skin over the existing curtain wall, which would create a "thermal break," preventing the metal in the curtain wall from transferring its temperature to the interior of the building.

The plan also calls for halving the electricity used by lighting, elevators, and escalators. A daylighting system that automatically dims illumination when there is adequate light will be installed and the tower's 104 elevators and 15 escalators, which carry tenants and visitors up and down 110 floors, will be stripped of their outmoded motor-generator sets and fitted with digital controls.

Smith + Gill estimate that it will take between 25 and 30 years to recoup the $350 million required for a total retrofit. But Sara Beardsley, the project's architect, says that it's worth it, since it will give the building "the highest standards of building equipment and technology that will last for the next fifty years." If all the changes are made, the energy saved will offset the operation of the proposed hotel tower, which could then operate off-grid.