The historic Old Chicago Main Post Office building, which occupies an entire city block in downtown Chicago, has been updated with 2,400 energy efficient, insulating windows. The windows transmit 70% of available visible light while blocking 62% of the sun’s heat energy.
The formerly shuttered, historical landmarked building has been brought back to life as a large office and retail complex. While it was exempt from meeting the local energy code requirements, developer 601W Companies was interested in the energy efficiencies leveraged by insulating glass units. Ultimately, the building was upgraded with 2,400 historically accurate windows fabricated with Solarban 60 solar-control, low-emissivity glass by Vitro Architectural Glass.
Low-emissivity (low-e) glass coatings were developed to minimize the amount of ultraviolet and infrared light that can pass through glass without compromising the amount of visible light that is transmitted. A microscopically thin transparent coating allows low-e glass to reflect exterior heat in warm temperatures and hold in heat during cold temperatures, making buildings light, bright and energy-efficient.
The windows meet all city, state and federal visible light transmittance and reflectivity criterion for landmark buildings. Glazing contractor Auburn Windows helped the architect Gensler and facade consultant Wiss, Janney, Elstner and Associates navigate the requirements.
By replicating the look of the original windows, the building also qualified for a number of historical tax credits, the developer says.
The building has also opened a 3.5-acre rooftop deck, an amenity considered especially important during a world health crisis. “People thought that health and wellness was a nice option to have in a building,” Sheryl Schulze, a principal at Gensler, told the Chicago Tribune. “It’s now an expectation.”
Uber, Walgreens, Ferrara Candy and Federal Home Loan Bank all lease space in the historic, 2.8 million square-foot building. Uber plans to move into the space in 2021, after having put off plans to move in in 2020 because of the pandemic.