Designed by Chicago-based architecture firm Jahn (formerly Murphy/Jahn), the Joe and Rika Mansueto Library floats at the center of the University of Chicago’s campus like a glass bubble. It is a dramatic counterpoint to the solidity of its neighbor, the Joseph Regenstein Library, a Brutalist-styled structure designed by architect Walter Netsch in the late 1960s. The new facility serves as an addition to the main campus library, and houses over 3.5 million volumes, providing the optimal conditions both for storing the collection and for reading it. Those “optimal conditions” meant keeping the two programmatic functions distinct from each other in their physical spaces: the reading room is above ground and almost completely transparent, while the books reside in an underground, climate- and light-controlled automated storage and retrieval system to meet the preservation needs of the books.

The robotic stacks, which retrieve volumes in about seven minutes, do not require light to function. However, trying to incorporate a nonintrusive lighting scheme into the reading room with its transparent glass dome proved a compelling challenge for lighting designer Michael Rohde and his team at L-Plan in Berlin, who have worked on a number of Helmut Jahn projects over the years.

It was late in the design process when Rohde learned that there would be no fabric shades to protect the reading room from sunlight. “We were about to start with the specification of products, then found out that the interiors were completely changed,” Rohde says. “It would have been a disaster in terms of lux level—we had to start all over.”

L-Plan embraced the design change—the architect’s choice of integrating custom fixtures into the furnishings and built elements—a minimal way of ensuring the right luminescence for a comfortable working environment. “One of our design targets was to create an ambience quality similar to sitting under a tree with no glare,” Rohde says. And while the lack of shading, save for a daylighting control membrane on the upper portion of the dome and a ceramic frit pattern on the glazing, may have added an unexpected twist to the design process, it helps on an energy-saving front: “If we have daylight, we don’t need artificial light, which is the best way of saving energy,” Rohde explains.

Working with a limited luminaire palette helped reduce the overall presence of light fixtures. Adjustable high-intensity 150W and 70W downlights reinforce the rhythm of the glass roof’s structural elements while delivering even vertical light distribution beneath the curved dome. Ventilation towers with indirect 26W T4 uplights increase the ambient light levels. At the circulation desk, 50W fixtures illuminate bibliophiles’ robotically retrieved selections; readers can then peruse their favorite tomes at desks also lit by individually controllable, custom LED tasklights. The fixtures were designed by a former Jahn employee, with a sensibility that blends seamlessly into the architecture and furnishings.

If the aim of the lighting design was to create a comfortable space where people can read and work as day transitions to night, then L-Plan has accomplished its goal. During a recent visit, Rohde found the library crowded well after 9 p.m., proving this celebration of the book a success.