China likes everything tall: tall buildings, tall people – there are even special summer camps aimed at growing taller children. These days the country also has an obsession with greenness (running parallel to its increasingly dire pollution problems). And soon these two cults – the cult of the tall and the cult of the green – will meet at Shanghai’s newest skyscraper, the 632-metre Shanghai Tower, billed by its makers as the world’s greenest tall building.

Skyscrapers are nothing new in China, where municipal gigantism has become such a fad that the country accounts for 13 of the 20 tallest buildings under construction in the world, according to figures from the Chicago-based Council on Tall Buildings and Urban Habitat.

At the time of writing, the Shanghai Tower, although still being built, is widely considered the tallest building in China and the second tallest in the world after the 828-metre Burj Khalifa in Dubai. However, a company in the central Chinese city of Changsha has announced plans to build the world’s tallest skyscraper, at 838 metres, in just three months. And Chengdu, another hinterland Chinese city, recently completed the world’s largest building by area, a scheme that included its own artificial sun.

Those behind the Shanghai Tower, however, want it to be more than another freakish Chinese vanity project. At nearly twice the height of the Eiffel Tower, they want it to do for brand Shanghai what that earlier tower did for Paris and complete a distinctive skyline that will symbolise China’s most futuristic city.

The tower’s spiral shape ‘minimises wind loads’

Greenness is central to that image, and the view from the top of the tower (which is due to be completed in 2015), leaves no doubt as to why that is: even on days when Shanghai’s smog registers as only “moderate” on the government’s air quality index, the view is murky and grey. It is an industrial revolution kind of view – and not one that is consistent with Shanghai’s ambition to become a world-class financial centre by the end of this decade.

The structure was designed to satisfy the US Green Building Council’s LEED (Leadership in Energy and Environmental Design) “gold” standard, the second highest of its sustainability rankings. “It’s the greenest super high-rise building on earth at this point in time,” says Dan Winey, Asia managing principal for Gensler, the architecture firm that has designed the tower.

The building – to feature 121 storeys of office, retail and hotel space according to Gensler – is constructed a bit like a Thermos flask. It has a “transparent second skin” – a double-glass façade, one of several green technologies that, says Gensler, will reduce the building’s carbon footprint by 34,000 tonnes per year. Its elegant spiral shape, which tapers at the top, was also designed with sustainability in mind. The building completes a 120-degree twist, and this, according to Gensler, is the “optimal rotation for minimising wind loads”, which will be cut by 24 per cent. “The result is a lighter structure that saved $58m in costly materials,” says a spokesperson for Gensler. The total cost of the tower is reported to be about $2.4bn.

The tower is split vertically into nine “neighbourhoods”, each with its own verdant, multistorey atrium or “sky lobby”, intended to evoke the landscaped courtyards of Shanghai’s historic homes (though it is unlikely they will be filled with hanging laundry and people playing Chinese chess, like the real ones).

CGI showing the ‘transparent second skin’

Each of the nine “sky lobbies” will have a garden planted in primary soil mixed with extra nutrients and compost, and irrigated by a drip system. The gardens will showcase plants from various parts of China, according to landscape architects the SWA group. There will be cafés, shops and restaurants to encourage tenants and visitors to congregate there. But each atrium or “sky garden” will also act as a “buffer zone” into which indoor air will spill before being exhausted from the building, also helping to cool it. Overall, one-third of the site is meant to be green space.

Exterior lighting for the tower will be provided by wind-driven generators. Overall, says Gensler, the building will employ 43 sustainable technologies designed to reduce energy consumption by 21 per cent compared with a conventionally built equivalent. But the architects, urban planners and even Gensler all point out that greenness is relative. “Building nothing is always the most sustainable course of action,” says Jun Xia, of Gensler’s Shanghai office. “It’s like a human being – a 7ft basketball star consumes much more resources than a regular-sized person.”

The Shanghai government, which owns a majority stake in the project through the Shanghai Urban Construction Investment and Development Corporation says it is more efficient to build a giant skyscraper at the intersection of two underground rail lines than to build smaller skyscrapers in the suburbs. The city’s vice-mayor told a conference last year that, with 23m inhabitants – an increase of almost 50 per cent in the past decade – and 9m migrant workers, the city had no choice but to build upwards.

View over the Jin Mao Tower and SWFC building

Nothing is ever that simple in urban planning. Li Guoqiang, director of the Research Institute of Steel Construction, part of China’s Ministry of Education, says Shanghai’s population density means tall buildings are necessary. “But the question is, do you need a super-tall building or an ordinary tall building?” he asks, noting that the costs increase with height. “In terms of economics, the best height is 100m,” he says, but quickly adds: “There is another value for tall buildings. If a building can be regarded as a landmark then it has another kind of value and that is hard to calculate”.

“For the first time in history, over half the human population lives in cities. Like it or not, tall buildings are here to stay,” says Jason Pomeroy, author of the forthcoming book The Skycourt and Skygarden: Greening the Urban Habitat. “With the Shanghai Tower, it’s a question of how you take this inherently energy-guzzling behemoth and make it sustainable . . . so the steps that have been taken to try to make it sustainable are the way to go”.

However green the design, what really matters is how the building is operated, argues Daniel Safarik of the Council on Tall Buildings and Urban Habitats. “If a building has 100 per cent operable windows and occupants don’t use them most of the year, the benefit of that design feature will have been lost,” he says.

So the verdict on the Shanghai Tower will inevitably be out until after it begins operating. Critics point to the Bank of America Tower in New York – the first building ever to achieve LEED “platinum” certification – and the subsequent claims that its environmental credentials were a case of “greenwash”. The New Republic magazine alleges in a recent article that the building consumes twice the energy per sq ft of the Empire State Building. But Scot Horst, of LEED at the US Green Building Council, defended the BofA Tower saying that it “removes stress from the existing electric infrastructure far more effectively than comparable buildings”.

Workers taking a lunch break on the 90th floor

Perhaps the most that the Shanghai Tower can hope for is to be greener than the competition – including the two super-towers that stand next to it; the Japanese-owned 492-metre Shanghai World Financial Center (SWFC), known as the “bottle opener” building, and the 421-metre Jin Mao Tower.

“If we want to make a city sustainable, we wouldn’t do it with super-high-rise buildings,” says Ken Maher, head of Hassell, the Australian architects behind several “green city” projects in China. “This is about making Shanghai more obviously a global city, and given that, let’s make it as sustainable as possible,” he says. “It’s not about saving the planet”.

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Patti Waldmeir is the FT’s Shanghai correspondent