150 North Riverside, Chicago

Nerves of steel and glass

Chicago’s North Riverside building transfixes viewers.

If the precarious-looking pencil-shaped design of Chicago’s new 150 North Riverside building doesn’t rattle the nerves, perhaps the building’s nearly invisible 8-story glass lobby will. Chicago’s new architectural and engineering marvel seems to defy both gravity and the city’s brutal winds while resolving an 80-year-old real estate problem.

Noted Chicago architects Goettsch Partners were called on to design an office tower that would fit in a prime Chicago riverfront parcel of land so narrow that no one had bothered to consider it for decades. By law, any building is required to be set back from the river for pedestrian access. Chicago’s trains also run through the parcel, further complicating an already perplexing problem.

The architect’s response was a unique core-supported structure with a seemingly impossible small footprint at the base of the building. This allows for a surprisingly generous pedestrian park on the river (east) side of the building. On the building’s city-facing side, a dramatic 90-foot glass lobby welcomes guests and tenants.

But this is no ordinary lobby. To respect the building’s unusual form, which dramatically cantilevers above the lobby, expansive and ultraclear nonreflective glass was used to enclose the entire space. There were multiple challenges. The structural span for the glazing was 85 feet and required large-format glass. A clear, invisible appearance with minimal joints, hardware, and color shifts was needed, as well as a seamless transition between the lobby wall and the plane of the curtain wall above.

Structural strength was also a major consideration. For the back wall of the lobby, the architects selected a new interlayer technology from Eastman Saflex® Structural interlayer, a tough, resilient film produced from plasticized polyvinyl butyral (PVB). It is designed specifically for applications where increased interlayer rigidity and high glass adhesion are required, as was the case at Riverside.

“Saflex Structural combines the benefits of a rigid interlayer with the features of glass containment, UV screening, edge stability, clarity, and impact resistance,” says Julia Schimmelpenningh, industry technical leader at Eastman. “A Saflex Structural interlayer in a properly designed system is capable of keeping glass intact at high and low temperatures in wet and dry conditions, even after impact and under load. All these factors were essential in this project.”

Two other Saflex interlayer innovations ensure the office space above the lobby offers acoustic control and crisp views of the surrounding city and river. Saflex Acoustic (QS41) PVB is an advanced, trilayer system designed to decouple and disseminate sound waves for superior sound-damping performance. The interlayers target sounds in the 1000–3000 Hz range, which is the most sensitive range of human hearing containing the most irritating sounds that penetrate windows. Occupants of 150 North Riverside can work in peace, enjoying a reduction of up to 10 decibels in the “transparent” frequency, which equates to a 50% reduction in perceived loudness. Saflex Clear (RA41), Eastman’s standard PVB solution, offers safety, solar, and security benefits to the glazing system.

The glass for the rear wall was provided by Glas Trösch AG (Bützberg safety glass: Luxar NR coating + 12-mm Eurowhite + 1.52-mm Saflex Structural DG + 12-mm Eurowhite + Luxar NR coating). The structural glass fins (3-ply fins and 4-ply truss panels) are suspended from the building structure with pointsupport glazing nodes to attach the face glass. The glass makeup provides a highly transparent (96.6% light transmittance), nonreflective glass that is strong enough to support the 8 story glass wall. The final effect achieved the architect’s vision: an invisible boundary between the interior and exterior of the building. From a distance, the glass lobby almost disappears.

“Once we’d defined how to make the glass strong and clear enough, we considered the load path and the connection design through the glazing nodes into the structural glass fin splices and, ultimately, into the pin connection at the head,” says Erik Harris, associate principal at Goettsch Partners. From any standpoint, 150 North Riverside is breathtaking and sure to be a must-see sight on Chicago’s famed riverboat architecture tours. Its dramatic shape and extensive use of glass have made the building an instant landmark that will inspire visitors, locals, and tenants for decades to come.