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Piano Pieces
For the Modern Wing, the design team devised uncommon mechanical and structural systems to suppport the architect's aesthetic goals of pristine lightness and transparency.
The loft-like spareness of the galleries was achieved in part by housing all mechanicals in six-foot-nine-inch-thick walls, leaving the ceilings relatively unencumbered.
Dave Jordano

Since its first permanent structure, the Allerton Building, opened in 1893—and through each of its subsequent expansions—the Art Institute of Chicago has displayed a strong dedication to exhibiting its collection under diffused natural light. The institution’s latest addition, the 264,000-square-foot Modern Wing designed by Renzo Piano Building Workshop, is perhaps the most thorough exploration of that commitment yet. While every previous structure in the complex—from the original Beaux Arts palace to the 1988 Daniel F. and Ada L. Rice Building—has been constructed in limestone, Piano’s contribution is an ode to steel and glass, serving as a link to the city’s legacy of modernist highrises as well as an embodiment of ethereal lightness.

To achieve this razor-thinness and transparency, the design team from Piano’s office, along with associate architect Interactive Design and engineers at Arup London, relied on a composite structure containing both reinforced concrete and steel sections. The eastern pavilion of the building that houses an education center and galleries is the most interestingly configured. The first two floors are framed in a combination of poured-in-place concrete and pre-cast concrete T-sections, which create 54-foot clear spans for the galleries. The choice of this material also allowed extremely narrow floor profiles, which were trimmed even further by omitting any horizontal HVAC ducting within the space.

All of the ventilation flues, as well as the concrete T-sections, were run vertically within a series of north-to-south running double walls, each measuring six-feet-nine-inches thick. Air is moved through slim vents running at the tops of the walls, and the only mechanicals left to clutter the ceiling were the sprinkler and smoke detection systems. Nonetheless, the building’s spandrels were kept to an attenuated ten inches.

Piano's daylight-diffusing device, the flying carpet, is composed of east-west running aluminum blades and north-south running aluminum fins, all welded to a grid of steel.
Dave Jordano

From the third floor to the roof, steel takes over for a smooth transition to Piano’s daylight-diffusing system, the “flying carpet.” Tapered tubular columns, on average 14 inches in diameter, rise from the concrete floor to meet, in exposed pinned connections, the grid of aluminum and glass that shelters the building. The flying carpet is composed of pre-mounted cassettes of aluminum blades running east and west.

Aluminum “dorsal fins” run perpendicular to the blades at greater intervals to maintain the diffusion of light throughout the day. The grouping of blades was also varied depending on what space they cover. Above the modern collection galleries, the blades are grouped more closely to better break up the light, an effect that is doubled by a layer of vellum that stretches across the top of the gallery. Above Griffin Court, the blades were spaced to allow greater light into this public gathering space.

The building also features two double-glass curtain walls on the north and south facades. Featuring two-and-a-half-foot-deep cavities, these walls increase the wing’s insulation values while maintaining its transparency. Again, thinness was key. The stick-built system was hung from above rather than supported from below, because when a structure is in tension, the profiles of its framing members can be kept slimmer than when it’s in compression.

Even so, since some of the spans supporting the mullions reach as much as 35 feet, the fabricator, Gartner, specified both steel and aluminum members. The panels of glass themselves—laminated, low-iron units with UV filtering properties and high color-retention films—are also slim, as little as two-feet-three-inches wide by 19 feet long. All of the glass had to be fired in Europe, as there are no domestic kilns capable of producing such sizes.

Edward Lifson explores the Modern Wing.

Aaron Seward

Aaron Seward is an associate editor at AN.