Chicago's 81-storey Aqua hotel and residence has won the prominent Emporis Award for best skyscraper of 2009, the global building data base said here Wednesday.
Emporis's jury hailed the 249.7-metre (819.33-foot) Aqua tower "for its advances in sustainable design and for the imaginative and fascinating architectural effects it achieves."
The building is expected to earn a LEED (Leadership in Energy and Environmental Design) Silver rating and "set a higher standard for the next generation of large-scale residential and hotel construction."
Despite the building's height it does not stick out in Chicago's celebrated skyline, Emporis data standards chairman Daniel Kieckhefer told AFP.
"Architect Jeanne Gang was aware of this, and turned it to dramatic effect - while the building looks ordinary enough from a distance, its fluid shape can deliver a breathtaking surprise to people who pass nearby and look up."
Emporis (www.emporis.com) gave a silver prize to the 23-storey O-14 tower in Dubai, and its bronze award to The Met, a 69-storey residential building in Bangkok.
Built near Lake Michigan, Aqua uses undulating balconies and glass planes to create a wave facade that has also been compared to a rippled curtain, a statement said.
The windows have also been given a blue-green tint.
Gang, of Studio Gang Architects, has said she was also inspired by striated limestone formations common to the US Great Lakes region.
The 10th Emporis Award, which Kieckhefer called the "Oscars" of skyscraper prizes, was chosen from among 305 towers completed around the world last year.
"The jury was very enthusiastic about Aqua, with a few members stating that they had been looking forward to its completion for years," Kieckhefer added.
As you move closer to the building, glass planes between the balconies catch sunlight and resemble smooth liquid surfaces, the Emporis statement said.
"As the tower starts to loom overhead, it changes shape; straight lines disappear, and a mass of rounded layers stack up vertiginously like a limestone palisade molded by centuries of flowing water," it added.
The cantilevered design shields windows from the summer sun without blocking light in the winter, while a light-coloured coating "reduces the heat-island effect caused by large buildings."
Special glass also enhances energy efficiency and prevents bird strikes, the statement said.
The amount of concrete needed for a structure that covers almost two million square feet (185,000 square meters) was minimized meanwhile by a technique known as post-tensioning.
"The tower sits on a broad podium with a vegetated roof, and the apartments' lighting and ventilation systems achieve double the required efficiency," Emporis said.
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