Tall buildings can be wildly polarising. Some people see them as beacons of a modern future and glittering symbols of a city's wealth and status, while others find them dehumanising and alienating. Yet some experts say that in a fast urbanising world - in China half the population now lives in cities - where there is rampant population growth, skyscrapers not only represent the planet's future but are also one of the more viable and sustainable visions of this future. Building up instead of out is an antidote to the problems of urban sprawl and an over-dependence on cars that have come to characterise many of the world's large cities in recent decades. And as the technology of building, cooling and heating tall buildings gets more efficient, and skyscraper complexes are increasingly combined with cutting-edge transport facilities, the benefits of building tall and minimising land use will eventually outweigh concerns about the large carbon footprint of constructing and operating skyscrapers. According to Paul Katz, managing principal at international architecture firm KPF, the architects behind Hong Kong's 118-storey International Commerce Centre, more people are moving closer to the city for convenience. 'Ironically, our virtual connectivity has affected the physical world in that people are looking to be closer to each other and use space in new ways,' says Katz. The environmental benefits of living and working in the same place are obvious: you drive less, or not at all, and don't need as much space. Half of KPF's work today is in Asia. The project that cemented its reputation in the region was Plaza 66, a 228-metre-high office complex in Shanghai completed in 2001 that has extensive entertainment and retail offerings. The skyscrapers of tomorrow will increasingly be 'vertical cities' that combine several uses, says Katz, adding that this is already more prevalent in Chinese cities than in the West. 'In an ideal city I'd imagine mixed-use buildings where lower floors were workplaces and upper floors, as the buildings got thinner, would be residential,' he says. Dominic Bettison, a director at British firm Wilkinson Eyre, the architects behind the IFC tower in Guangzhou, agrees with the importance of combining uses in tall buildings, but says it isn't just about social or environmental concerns; for developers and owners it's also about spreading risk. 'If you're going to do a 102-storey building full of offices you've got to be pretty confident that the market can support that amount of office space,' Bettison says. 'But if you can hook a big hotel operator to take a third of the building on a 60-year lease then that's fantastic. In many ways it's paid for your building; the rest is profit. It creates a more varied, rich and interesting building to live in, to work in and to socialise in.' One way of making skyscrapers more human is to deal with the spaces around them, says Katz. 'What's important is the way the building meets the ground and how you enter the building,' he says. Exciting outdoor spaces, bridges between buildings, and sky gardens all help make the outdoor experience more enjoyable. 'You have to work quite hard to make sure the spaces around the base of a building don't just become windy plazas,' says Bettison. 'If you look at New York, some of the spaces can become quite brutal and stark. So you've got to work on the hard landscaping and soft landscaping, and make the plazas interesting and functional places to be in.' The more accessible a building is to the public, whether through hotels, bars or terraces, the more it becomes integrated into the city, Bettison says. He cites the examples of Renzo Piano's Shard Tower in London, which will combine offices with residential, restaurants, an observatory and a hotel when it is completed this year, and the ICC in Hong Kong with its Ritz-Carlton hotel and bars on the top floors and its viewing deck on the 100th floor that allows people to admire the views without spending too much. Two IFC across the harbour, despite the successful mall at its base, is comparatively fortress-like, he says. At present, KPF is working on a project in Causeway Bay called Hysan Place that will have sky gardens and big apertures designed to improve the quality of the air around it. It's also working on a 460-metre-high headquarters for one of China's largest companies, China Resources, due to be completed in Shenzhen in 2017. Bettison is heading up two new tall building projects in Wuhan and says his firm is keen to push the agenda of tall buildings, in terms of environmental design as well. He talks of low-energy lift systems that generate electricity on the journey down and using energy-efficient cooling systems, and points to the longevity of many tall buildings. 'Compared to some of the last generation of low-rise buildings in cities that have lasted only 30 or 40 years, a tall building designed flexibly, with mixed use, could look forward to a life of 100-plus years. There is potential for it to be quite sustainable in terms of its life.' What would be an ideal way forward for China? 'Up to now in Hong Kong there's been residential neighbourhoods and workplace neighbourhoods and they've been pretty distinct, unlike in New York where there's a blend of the two,' says Katz. 'My hope is that in Hong Kong and other parts of China people will build residential neighbourhoods next to places of work and places of study and places of culture. Then these areas will truly be intertwined and become multi-disciplinary districts. I think you can use the city in a much more complex way by mixing up the uses.'
