High hopes

With finance hard to come by and sustainability paramount, supertalls seem to have the odds stacked against them in 2010.

When Dubai's Burj Khalifa reached its final height of 828 metres - becoming the tallest building in the world by over 200m - it did so against a background of global financial uncertainty. As a result, by the time the iconic tower was finished most of its competitors had fallen by the wayside.

Among them were plans for a 1,001m tower in Kuwait and Dubai's Nakheel Tower, also clocking in at over one kilometre. Another kilometre-high tower, in Saudi Arabia's coastal hub of Jeddah, is alleged to be ongoing, but information about the project is limited.

But building supertalls is an expensive business, and with financial uncertainty ongoing, it would be no surprise if the Burj holds onto its world's-tallest crown for some time. At over 800m, the Burj is significantly bigger than the Taipei 101, the current world's second tallest, and the Shanghai Tower (632m) currently under construction in China's financial hub.

"It is likely that the global financial crisis, current problems with rentals and asset values, and the lack of capital generally will mean that building super-tall will be out of fashion," said Richard Marshall, an engineer at Buro Happold.

Marshall added that if anyone is going to buck that trend, it is likely to be either China or certain areas of the Middle East, such as Saudi Arabia.

"With capital and a relatively unconstrained decision making elite, they are more probable locations for the next generation of super-tall buildings," he said.

Although it will clock in at a good few metres lower than the Burj, Gensler's Shanghai Tower, in the city's Lujiazui district, is already proving that point. The tower will overshadow the Shanghai World Financial Centre (492m), currently the third tallest building in the world, by some 150m.

Gensler's Chris Chan, who designed the tower, admitted that financial considerations are paramount when drawing up a design for a tall building, but he added that in a city where space is seriously constrained in comparison to the population, tall towers become all the more viable.

"Pound for pound a tall building will cost more in terms of construction, but you also have to factor in the amount of land area you are creating," Chan said, adding that the Shanghai Tower is creating 380,000m2 of space on a tiny footprint.

It is an argument that Eric Kuhne, the designer behind the proposed City of Silk tower in Kuwait, agrees with. "They are hugely expensive, but because the City of Silk was conceived as much as a diplomatic symbol as it was a functional piece of architecture, obviously that mobilises more capital," he said.

Kuhne's tower is planned to be the centrepiece of a 250km2 development on the Kuwaiti coast, which will include a new airport, a business district and thousands of units of new housing, offices and commercial units. It is made up of seven 30-storey buildings, separated by four-storey sky-gardens and supported by twisting three towers together. The project was commissioned by the Kuwait government before the financial crisis shook the country, and is currently still in the design phase.

Financial constraints are something that Woods Bagot, the firm behind the 1,000m Nakheel Tower, knows about first hand. Half of  buildings foundations had been built when it fell through at the end of last year. More than six months on the firm is still hoping that the tower will eventually be finished.

"As always it comes down to someone wanting to do it. Clearly going up to this kind of height is extreme and the way that a project like this stacks up financially is not just the tower, it's all the other stuff around it," said Alfred Seeling, design director at Woods Bagot.

The Nakheel Tower scheme included a significant amount of real estate surrounding the building, including housing, office and retail space - like Downtown Dubai, the value of this real estate would be boosted by the presence of the world's tallest building, helping pay for it. "This is one of the only places where you can get hold of these large parcels of land, you couldn't do this in New York, you just couldn't make it stack up on a small floor plate in Manhattan," Seeling said.
But it is not just the financial crisis that has taken the wind out of the sails of tall buildings in 2010. The ongoing focus on green design has also played a role. Governments, developers and designers are keener than ever to boost their sustainable credentials, and building supertalls is not seen as a way of doing it.

"There is an argument that tall buildings are unsustainable, but there is also the reverse - if a tall building is designed sustainably and in particular if there is an associated reduction in infrastructure and transportation usage as a consequence then ‘real' energy use could be considered lower," said Buro Happold's Marshall.

City of Silk's Kuhne is firmly in the latter camp.

"When you concentrate people in a central space you get the highest efficiency of sustainability because of the fact that you have more people in one place and their movement, which is the biggest negative of energy consumption is reduced down to the most efficient level," he said.

But Kuhne is not hedging his bets either. The City of Silk designers have calculated how much carbon will be used by an estimated one million people that will use the tower and surrounding area, and planted enough trees to offset it.

"We know that in the Middle East it takes three trees to carbon balance for every individual. We pushed the tree proportion per person to seven, so for that group estimating a million people that's 7 million trees that we're going to plant there," he said.

Woods Bagot's Seeling also believes that the argument depends on how narrowly you define sustainability. Unlike some other supertalls, the Nakheel Tower contains more than 200 floors of usable space, with floor plates around 3,600 m2.

"You're not taking up so much land, a building like this has got a population of 12,000. If you were to spread that out over a normal density it would take up a lot more land all your infrastructure has to be much more spread out," said Seeling.

The last challenge for the next generation of supertalls is engineering, and first among these practical concerns is wind. As a tower rises, the impact of wind increases, with gusts varying in direction from top to bottom. The Nakheel Tower and Kuwait's City of Silk have devised very different solutions.

"The way the tower is designed with the three blades like the three spokes, that come out are like a tripod, bracing the building against the wind. So instead of tapering to a sharp point, we're got these blades that are orientated towards the principle wind directions and they help brace the tower," Kuhne explained.

The designers also fashioned aerolons that imitate the technology used on airplane wings and move dynamically with the wind on the six corners of the tower.

Woods Bagot came up with a different solution to the problem of wind. Rather than allowing it to go around the tower, it goes through the middle. A close look at the Nakheel Tower reveals that it is in fact four towers, joined together at 25 floor intervals by sky gardens. The wind flows through the center of the tower, and the sixteen corner walls that form the core of the building.

Of course, it remains true that despite the detail and ambition of current plans for supertalls, none are underway in any tangible sense. The question is whether, with the economic and environmental factors stacked against them, there is still a future for tall buildings.

Gensler's Chan feels sure there is.

"If history is an indication of what our future will be like, then there will always be new technology and new techniques for making buildings taller," he said.

"Since the dawn of mankind, since the Pyramids, there's always been something in our human condition that makes us want to build higher and taller, in order to reach the skies."