The Lotte World Tower rises from bustling Seoul, South Korea, as a sleek new city icon. For the team behind the 123-story building at global architecture firm Kohn Pedersen Fox (KPF), creating this seamless silhouette meant a challenge of engineering ingenuity—and quite a bit of glass.
“Even though it looks like one big monolithic tower, there are 20 different types of glass on that tower,” explained KPF’s Richard Nemeth, managing principal for the project, which opened earlier this year. The 1,821-foot-tall silhouette was inspired by traditional Korean forms like pottery and paintbrushes, but its multiple functions helped dictate the form as well. Office space is located at the bottom, while the tower tapers in two directions—“think football instead of baseball”—offering smaller spans from core to glass toward the top of the tower, where the residences, hotel, and observation deck are located.At the base, a 100-foot-tall lobby utilizes a gradient of mirrored frits on the glazing to provide shading while accommodating views at ground level; at the top of the tower, frits were used to highlight the diagrid of the belt trusses. The residences utilize laminated safety glass on the inner lite with heat-strengthened glass on the outer lite, while the hotel and office sections use heat-strengthened glass for both. To keep the building from looking like a “giant patchwork quilt,” Nemeth said, the KPF team ensured that the outer lite is always the same thickness, with the reflective coating on the number-two surface. “Then, whatever you do on your inner lite is much less visible to the outside, because it’s inside the reflective coating,” he explained. While the world’s fifth-tallest building includes a number of innovative energy-saving strategies, for many visitors the tower’s crowning achievement is the glass-floored observation deck—the world’s tallest. Cantilevering out, it offers views some 1,600 feet down—with just three layers of 10-millimeter-thick tempered glass with SentryGlas Plus interlayers separating viewers from the ground.