Chicago's James R. Thompson Center will undergo a floor-by-floor gut rehab beginning early next year, but the building will retain its atrium while also opening up the base of the structure to retail, according to renderings released by Google Wednesday. Google will occupy the Central Loop icon once the renovation of the building is complete.

Historic preservationists who fought to save the Helmut Jahn-designed building from the wrecking ball praised the development team for its plan to preserve the 17-story atrium.

"This design looks very different from the initial schematics we saw a year ago," said Ward Miller, executive director of the nonprofit Preservation Chicago. "That's to be commended, and I think it's wonderful the atrium is to be saved. My hat's off to Google and the developers for taking on this project and committing to not demolishing the building and rethinking it as a corporate headquarters."

A venture led by Chicago developers Michael Reschke and Quintin Primo bought the Thompson Center in 2022 from the state of Illinois for $105 million, and Google agreed to take it over after the renovation is complete in several years.

The developers will replace the building's glass façade, and renderings show a new glass curtain that lets in more natural light, a new public plaza with trees and spaces for food and beverage retailers, and covered terraces on the first three levels of the southeast side.

"With more natural light, access to green space, and biophilic design elements that borrow from nature, the original design's ode to transparency and openness will live on," said Karen Sauder, Google's Chicago site leader, in a prepared statement.

One unknown is how the internet giant's arrival will impact the Central Loop. The submarket was hit hard by the rise of remote work, which leaves downtown quiet several days each week. Many property owners hope Google will ignite a revival, much as it did for Fulton Market by opening in 2015 its Midwest headquarters in a former cold storage building renovated by developer Sterling Bay.

But history may not repeat itself, said Joe Learner, Chicago-based chairman of North American brokerage for Savills, a commercial real estate firm. Fulton Market was filled with small industrial structures that developers could replace with sleek, high-tech office towers, hotels and restaurants, all enticing for companies looking to bring back at-home workers. But the Central Loop is dense, with less natural light and many aging buildings from the last century.

"The question is, is Google's very presence enough to spur interest in these other buildings?" Learner said. "The redevelopment of the Thompson Center is fabulous for the city, but I'm not sure it will have the same multiplier effect."

Fencing will go up around the Thompson Center early next year prior to construction crews starting work, Sauder said.

Jahn, the architectural firm founded by Helmut Jahn, will help redesign the building and preserve its character, she added. Helmut Jahn died in 2021 after being struck by two vehicles while bike riding in the western suburbs.

The new exterior will be triple-paned glass, and provide more insulation than Jahn's original material, keeping the mammoth structure cooler in summer and warmer during cold snaps, but using less energy. The outdated heating and cooling equipment, which sometimes made life miserable for state employees, will also be replaced.

Google has not shared many details about what the interior will look like, how it plans to use the 1.3 million square feet, or whether it will still be called the Thompson Center.

Miller is urging the developers to preserve other historic aspects, including Jahn's palette of colors, and the spiral tile design at the atrium's base, meant to resemble the ceiling of a state capitol dome.

"It's a wonderful optical illusion," he said. "The building may not have been maintained well, but it's a true work of art."

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