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1 1 of :06 Popular Mechanics: Hearst Tower - Re-inventing The Skyscraper The 46-story Hearst Tower is an energy-efficient, structurally strong, environmentally sound addition to New York City's skyline. And if we may say so ourselves, it looks pretty cool, too. By David Noland Published in the April 2006 issue. After the 46-story Hearst Tower was topped off in Manhattan in February 2005, one climber crane lowered a second crane to the ground. No vertical beams were used in the exterior tower structure--a first for both U.S. office buildings and construction workers. PHOTOGRAPH BY DEAN KAUFMAN Rising among the staid rectangular buildings of midtown Manhattan is an anomaly in the urban landscape: a sleek, faceted skyscraper glittering above a squat, ornate plinth. Architecture critic Paul Goldberger calls the new Hearst Tower the most beautiful addition to the city skyline in 40 years. But accolades extend beyond the curtain wall: Cutting-edge engineering makes it a model of sustainable design. Victor Ganzi, president and CEO of PM's parent company, Hearst, approved the tower just one month after 9/11, committing to keep its headquarters and 2000 local employees in New York. The project posed a unique challenge for British architect Norman Foster, internationally acclaimed for graceful, modernist designs. The contemporary skyscraper was to sit atop the original Hearst building, a six-story 1928 art deco landmark. Foster's solution was to leave the limestone facade intact, but to carve out the building's center to create a vast atrium, and then lift the new tower above it with huge steel-and-concrete beams. The resulting nine-story interior, with its 30-ft.-high waterfall and clerestory windows, promises to be one of the most dramatic spaces in New York. "The concept," Foster says, "was to create an 'urban living room.'" The tower's distinctive framework is a "diagrid" of interlinked triangles, so structurally efficient that the building uses 20 percent less steel than conventional designs require. Floor-to-ceiling windows cast light on 95 percent of the occupied space. Thanks to dozens of energy-saving features, from motion sensors to high-efficiency ventilation equipment, the total energy consumption of the building will be 22 percent less than that of a typical skyscraper of comparable size-a savings of 2 million kilowatt-hours of electricity a year. Elements throughout the building reduce the use of resources: Carpets, ceiling tiles and furnishings were made with recycled materials; rainwater collected in 14,000-gal. tanks will humidify the atrium. The tower is on track to become the first commercial skyscraper in New York to receive a "gold" rating under the U.S. Green Building Council's program for Leadership in Energy and Environmental Design. For two years now, from offices a few blocks away, the Popular Mechanics staff has watched the tower take shape. We think it's fitting that our new home will be one of the world's most magnificently engineered buildings.

2 2 of :06 STEEL CONSTRUCTION The tower's diagrid structure consists of four-story-high interlinked triangular frames (above). Because the triangles carry the gravity load while also providing lateral strength, beams don't need additional bracing, which saved 2000 tons of steel. "The geometry was difficult," says construction manager Scott Borland. "We've built a lot of boxes, but this was not a box. For everything to fit in the end was pretty amazing." PHOTOGRAPH BY MIKE FICITO The tower is supported by 12 "megacolumns." Too heavy to be shipped whole, the 85-ft. columns arrived in segments that were unloaded on the street and "tripped up," or stood on end, before being hoisted into place, welded together and filled with concrete.

3 3 of :06 CLOSE FIT The megacolumns connect to eight 90-ft.-long "superdiagonals." Clad in stainless steel, they slice dramatically through the building's atrium. Massive Y-nodes made of 2- and 3-in.-thick steel plate provide the points of connection. Because of the huge structural loads, the 12-ft.-high, 20-ton Y-node fittings are built to a tolerance of 1/8 in., three times tighter than in conventional skyscraper construction.

4 4 of :06 WATER CIRCULATION Engineers tested the design of the lobby's 30-ft.-high waterfall using a model (above). The full-scale version flanks both sides of the escalator, contributing to aesthetics and important building functions. Replenished by rainwater collected on the roof, the water feature helps maintain an ideal relative humidity of 30 to 50 percent, depending on the season, and cuts the atrium's summer air-conditioning load by 5 percent. Water circulating through polyethylene pipes embedded in the atrium floor provides radiant heating and cooling (below). In winter, this system warms the granite floor to 78 F, supplying 36 percent of the atrium's heating. During the summer, it chills the floor to 72 F, supplying 10 percent of the atrium's cooling.

5 5 of :06 PHOTOGRAPH BY DEAN KAUFMAN GOING UP An escalator will lead employees from the street-level entrance to the third-floor atrium level. Manufactured in one piece, the 56-ft.-long

6 6 of :06 escalator had to be hoisted into the gutted interior of the 1928 building while the roof was off. It sat protected by plywood for more than a year before it was installed. CURTAIN WALL The diagrid pattern intrinsic to the tower's basic construction is traced on the exterior by stainless steel cladding (above). "By expressing the structure in a sculptural way and casing it in reflective stainless steel, it becomes the identity of the tower," Foster says, "especially from a distance." Installing the cladding required a custom-built, double-tier monorail scaffold system that could move side to side as well as up and down. Because of the building's shape, the installation of windows proved tricky, too. "On any given floor you can have as many as 30 different window configurations," says Syed Alkarimi, the architectural coordinator in charge of the facade. The double-pane glass has a low-e coating to let visible light through while reflecting heat-causing wavelengths. Laminate on the inner pane is twice as thick as is typical; it should remain intact in the event of a disaster, while the outer pane is designed to shatter.

7 7 of :06 MULTIFACETED The 46-story edifice incorporates the original Hearst building, finished in 1928, which was intended to support a tower that was never built. "The challenge was to respond, at some 70 years' remove, to the original vision of the building," Foster says. He did so by creating a transition zone of clerestory glass that floods the atrium with daylight. "By lifting the tower up 10 floors, we achieved a separation from the original building, and the tower appears to float above it." Because there are no columns on the perimeter, the corners instead form eight-story-high "bird's mouths." Cleaning them requires a custom-built scaffold. The system has a raised track on the roof and articulating arms to move the platforms in and out with the glass. "It's like a ride at Disneyland," Borland says. Adds Alkarimi, "It's a little scarier than that."