Skidmore, Owings & Merrill is behind the world's tallest building, the Burj Khalifa, so obviously knows a thing or two about building big. New York City's One World Trade Center shows that the firm is also pretty handy at building green too, and the western hemisphere's tallest building was recently awarded LEED Gold certification (a major green building code) in recognition of its sustainable design.

Taking its name from the North Tower that was destroyed on September 11, 2001, the One World Trade Center rises to a symbolic height of exactly 1,776 ft (541 m). Symbolic because 1776 was the year that the United States made its Declaration of Independence from Great Britain. Its overall form is inspired by both the tapering style of classic New York City skyscrapers like the Chrysler Building and the original Twin Towers.

The crystalline skyscraper is anchored by a cubic base with roughly the same footprint as the original North Tower. A podium with 4,400 decorative glass fins rises to an octagon in its center, before the tower culminates in a spire.

The building's green credentials begin with a glass curtain wall that envelopes the tower on all sides from the 20th floor to the observation deck. This glass is coated to ensure that, while natural light reaches over 90 percent of the building's office areas and thus reduces artificial lighting requirements, ultra-violet and infrared light is reduced, as is glare.

A building management system optimizes energy use and indoor air quality by monitoring thousands of sensors dotted throughout the building. All stormwater runoff is captured and stored in three retention tanks to be used for cooling and irrigation.

Over 40 percent of the materials used in construction were recycled, including gypsum boards, ceiling tiles, and glass. And more than 87 percent of construction waste from the project was diverted from the landfill.

While thin is in with skyscraper design at the moment, hard lessons have been learned from the 2001 attacks and SOM over-engineered the building to far exceed NYC Building Code requirements. All life-safety systems, including exit stairs, communication antennae, exhaust and ventilation shafts, and elevators, are encased in a concrete core that's a minimum of 2 ft (0.6 m)-thick.

Approximately 430,000 tons of concrete was used in the build, along with 46,000 tons of steel (most of which was recycled). The tower's elevators move at a maximum speed of 2,000 ft (609 m) per minute and can reclaim energy through regenerative braking to reduce demand on the grid. Roughly 787,200 sq ft (73,133) of glass is used on the skyscraper, or an area equivalent to almost 14 American Football fields.

Source: SOM

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