Crown Hall
Photography: Arturo Duarte Jr. via Wikimedia Commons

It’s said that windows are the eyes into a building; they’re also often the most striking element, especially when it comes to a stylish midcentury modern edifice that broke the architectural mold.

But now that decades have passed and those gems from the mid-20th century are in need of a tune-up, architects are stuck with a conundrum: What should we do with windows that pass the visual test but fail the functional test. At a moment in the profession when sustainability and efficiency are finding their way into the preservation conversation, how do we best manage our modern heritage?

In 2005, Chicago-based Krueck + Sexton took on a mighty task in this field: Crown Hall, a masterwork from famed architect Ludwig Mies van der Rohe and the home of the Illinois Institute of Technology College of Architecture. The undertaking ultimately fell to founding principal Mark Sexton, FAIA, an award-winning architect who wasn’t afraid to take on daunting projects.

“There is an art to restoration,” he says. “You have to deeply understand the building and design around it.”

When it came to Crown Hall, that meant windows. The walls are largely glass, the dazzling result of Mies’ skeletal design but a concern when it comes to both modern building codes and the abuse sustained from housing hundreds of architecture students over the years.

Sexton knew that the line between success and failure on this project was thin; the windows were too reflective and miles behind technologically, but altering the aesthetics would raise the ire of the architectural community. Luckily, the fix proved both simple and indiscernible to the naked eye: employ thick upper windows made of low-iron glass that resembled the original panes plus thin lower windows that unify both the top and the bottom.

“Mies used raw sandblasted glass,” he says, “and sandblasted coating technology had improved so much by then, we could coat the sandblast and have it appear as it was. It was a case where we actually improved it by bringing it back to the original, and improved the original because of technology.”

Yet while modern window expertise resolved what could’ve been a sticky situation, the murky intersection between improvements and blasphemy reared its head in another way. Sexton suggested an automation system with light sensors for the building’s venetian blinds, which need to be opened and closed at various points throughout the day, to greatly enhance its energy performance. The faculty did not take kindly to his proposal.

“They argued we were actually sabotaging the essence of the building by automating it,” he says. “We argued that, given the conditions of the world, we had a moral obligation to develop some path—respectful of the original architecture—but a path to save energy. It’s an obligation that wasn’t on the radar 60 years ago when [the building] opened.”

Sexton wasn’t automating for convenience; he was doing so for function. But his proposal remained only that, despite similarities to another tweak they had already made.

“To meet building codes, we needed the bite of the windows to increase,” he says, “so we sloped it. It’s not visible at all; even the die-hards who were against the idea at first admitted that. So even though they said, ‘How dare you put a sloped stop in this building?’ for us it was easy: We were breaking the rules because you couldn’t really see it.”

That’s how difficult a restoration project can be: It’s possible to sneak in an imperceptible—and beneficial—tilt to your windows, but equally advantageous blinds that open on their own are roundly rejected.

It comes back to the question: What are we ethically allowed to alter with our current level of sustainable know-how? Or, perhaps more pertinently to some: What would Mies think about all this?

“I learned from Gunny Harboe, FAIA, ‘Never question a dead architect,’ ” Sexton says. “[Because] they’re dead! We have an obligation to preserve the exact proportions of the building, but a higher obligation for life safety. And, to me, energy savings is part of life safety.”