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When the $3-billion One World Trade Center (WTC), formerly known as the Freedom Tower, is completed, the structure will reach 105 floors and 417 meters, about the same height as the roof of the original WTC North Tower. But the new building will host a taller spire than its predecessor, bringing the total height to 541 meters (or 1,776 feet, in a nod to the year 1776 when the 13 colonies declared independence). With the addition of the spire, One WTC will surpass Chicago’s Willis Tower—formerly known as the Sears Tower—as the tallest building in the U.S.
One WTC is not yet completed, but it is already the tallest building in Lower Manhattan. “We have something in our kitchen showing all the buildings in Lower Manhattan, and we’ve been ticking them off as we pass them,” says Lynda Tollner, program director of One WTC for the Port Authority of New York and New Jersey. “Now we need one for the rest of New York City.” The steel frame of the tower now exceeds 80 floors and tops out at about 300 meters.
The first steel columns for what was then called the Freedom Tower were installed below ground level in December 2006. Later came 24 “jumbo” steel columns, 18 meters long and 64 metric tons apiece, that formed the building’s perimeter. But that was just a fraction of the steel needed to construct One WTC. When it is completed, the tower will contain more than 40,000 metric tons of structural steel.
Inside the steel frame of One WTC are one-meter-thick concrete walls encasing the elevators and stairwells as well as communication and safety systems. In total, the building is expected to require 150,000 cubic meters of concrete. “What we’re doing with this concrete core is so different,” Tollner says. “It’s almost like we’re building a nuclear power plant or something. It’s not like building a regular office building.”
The Port Authority is aiming for LEED Gold certification at One WTC. Green initiatives in the new building include rainwater reclamation and distributed power generation with on-site fuel cells. The authority says the skyscraper will exceed code requirements for efficient energy consumption by 20 percent.
The design of One WTC incorporates several new safety features intended to speed a potential evacuation. Extra-wide staircases interconnect at various floors so evacuees could cross over if one of the stairwells were blocked. All the stairs have exits direct to the street rather than opening into the lobby. And the building has a dedicated stairwell for first-responder use in the event of an emergency. “That would be the stair that they would be climbing up, and no one would be coming down,” Tollner says.
The tenant floors of One WTC, which total 240,000 square meters of office space, begin on the 20th floor. Magazine publisher Condé Nast signed a 25-year lease in May for roughly 95,000 square meters of office space on floors 20 to 41. The deal is worth an estimated $2 billion. The Port Authority expects to have a temporary certificate of occupancy for tenants of the building in late 2013.
The WTC was the site of a deadly bombing in 1993 as well as the attacks of September 11, 2001. The new building is fortified against truck bombs. “What’s very unusual for a building like this is the blast walls at the base,” Tollner says. On the north and south sides, where One WTC is closest to the street, the blast walls are 15 meters high, a safety measure with some aesthetic trade-offs. “I don’t have a light-filled lobby,” Tollner says. “I have a very tall lobby, and that’s in remembrance to the lobbies of the original buildings.”
Above the blast wall and the lobby is a layer of infrastructural floors reaching to 57 meters above ground; this lower section will be covered in reflective glass. “The idea is to make it lively. The architects didn’t want it to look so dead at the bottom of the building,” Tollner says. The original plan to sheath the base in prismatic glass fell through earlier this year after millions of dollars failed to produce a satisfactory glass product. “This new design is completely different,” Tollner says. “It’s going to have glass fins, and they will have a very nice reflective quality. They’re not going to be completely flat against the building, and they’ll have a frosted texture behind. When they light up the building from within you’ll get some interesting patterns.”
The steel frame of One WTC grows by about one floor a week; the building’s concrete core keeps pace eight to 10 floors below. “The concrete follows the steel, and we try to keep them not too far apart,” Tollner says. “It’s like a dance all the way.” After that comes fireproofing and then the glass exterior, or “curtain wall.” Keeping the project moving ever skyward requires about 1,300 workers on a daily basis, Tollner says. Overall there are about 3,000 workers on the entire WTC site, which includes three other skyscrapers, a performing arts center, a memorial and museum, and a transit hub.