Engle envisioned the new tower long before ground was broken, using his years of experience to imagine the final structure. Before specifying fixtures, he worked backward from a fundamental question: What should the building feel like? “We were searching for what this building would mean on the horizon,” he said. “What the lighting is going to do affects the building and what the building is going to do affects the lighting.” The tower had to be recognizable from three places: at its base, from a short distance (such as 34th Street), and from afar. Each required a different lighting solution. At the base, the lighting had to have an open, welcoming feel. From a distance, the tower’s many interior lighting conditions had to be legible as a single, integrated form. Configuring light is more an art than a science, “something that the computer just doesn’t quite know how to do, so you’ve got to know how you see what you see and turn it into reality.”
In December 2012, the last two escalators for One World Observatory were hoisted by crane up to the 100th floor. The sight of an escalator floating in the sky captured people’s imaginations—photos of the operation, taken by Scott Lahmers, a technical specialist at ThyssenKrupp Elevator, went viral.
When Engle broke the news that the lobby isn’t lit naturally, I was dumbstruck. The illusion is that real. “It’s already working. It fools you, it does,” he said, chuckling, like a magician pleased with his own trick. Given the thickness of the exterior concrete walls, it wasn’t possible to cut windows into them, so the designers did the next best thing: they imitated sunlight using LED lighting, which supplements the daylight that enters from the east and west portals. In addition to greater energy efficiency and longer life, LEDs can be programmed to throw both warm and cool light. To create the illusion of sunlight, cool light is used during the day; it crossfades to a weaker, warmer light at night. The lights are timed to mimic daylight; as the sun sets, the lights change slowly over a twenty-minute period so that the eye adjusts, rendering the change imperceptible.
ThyssenKrupp designed and installed the tower’s seventy-one elevators and twelve escalators. Fifty-eight of them are passenger cars that use Destination Dispatch, a smart technology that brings occupants to the upper floors in the shortest possible time, using data encoded in the passengers’ building passes. Grouping passengers in this way eliminates stop-and-go delays associated with traditional elevators, saving time and energy, and increasing security. Those working on the highest floors take an express cab to the sixty-fourth floor and switch elevators, a necessity created by the tower’s slender upper profile. Visitors to One World ride dedicated elevators, the fastest in the Americas, reaching the observatory in less than a minute. The elevators are as quiet as they are fast. Aerodynamic aluminum shrouds deflect air and maintain speed, much as a spoiler on a car does. A special guide system minimizes vibrations, ensuring a smoother ride, while sound-suppressing materials limit noise. A global team of collaborators from Brazil, Germany, China, and the United States developed the state-of-the-art elevators, which were tested in a 25-story skyscraper in South Korea.
GLASS CURTAIN WALL
From a distance, or in photographs, the tower appears to be formed of uninterrupted planes of glass. The effect is the result of using large window panels on the upper floors and concealing the spandrels, or horizontal support elements, that are seen on older buildings. Containing just under one million square feet (92,903 m2) of glass, the curtain wall is composed of 13,000 insulated panels of crystal clear glass. It was engineered in tandem with the structure, which supports the weight of the curtain wall, and the three louvered mechanical levels.
To meet a range of safety and load requirements, the tower incorporates different types of glass. Laminated and tempered glass were combined in five thicknesses to resist various forces as the tower rises. The glass is heavier at the base for security reasons and at the top, where the tower bears the wind’s full, unobstructed force. At each corner, trapezoid-shaped glass lights extend ten inches (25.4 cm) beyond the mullions and appear to float in front of the stainless steel corners, softening the tower’s edges.
The public got a sense of just how slick and strong that glass surface was in November 2014, a week after the tower opened to its first tenants. Two window washers were stranded at the sixty-eighth floor when one of four cables holding up their scaffold failed, leaving them teetering on their washing rig for almost two hours. Using diamond cutters, FDNY firefighters sawed through the double-layered window and pulled the men to safety—a feat that made the city breathe a collective sigh of relief. Luckily, Benson Industries, which engineered, fabricated, and installed the curtain wall panels for One World Trade Center and Four World Trade Center, was prepared for such an eventuality, having designed the units with a four-sided structural silicone so that individual pieces of glass could be replaced.