You have just closed the door behind you and your dog is already jumping up your leg, demanding you take him for a walk. Normally this would mean a short journey in the lift or a few flights of the stairs. Not so if your apartment is in one of the world’s new super-tall buildings, where you might be hundreds of metres above ground. It’s no walk in the park to take a walk in the park.
You might think today’s skyscrapers are tall, but they are likely to be dwarfed by concepts and future designs pushing human construction higher and higher. In May this year, One World Trade Center was topped out and has become the world’s third-tallest building at 541m, restoring New York’s skyline and placing it back on the map of super tall buildings. The mantle of world’s tallest building is now held by Dubai’s Burj Khalifa, completed in 2010 and which reaches the lofty height of 829.8m. The presence of this enormous building and the fact that even more buildings of comparable heights were under way made the Council on Tall Buildings and Urban Habitat (CTBUH) introduce the – so far – latest category of high-rises: the mega-talls, buildings exceeding 600m in height. And this is likely to be just the beginning.
Obviously the quest for new heights is not at all new. What is different though is that the competition for tallness turned global and consequently fiercer and more extreme. Cities and regions compete against each other and require buildings as landmarks that create identity, symbolise power and riches and showcase sophistication way beyond their physical boundaries. At the moment the race to build skyscraping towers is about prestige; but one day they may help alleviate urban sprawl, allowing our megacities to curb their seemingly unstoppable spread.
The title of the world’s tallest building already has a new challenger; the Kingdom Tower in Jeddah, Saudi Arabia, which is intended to be the first to reach beyond the 1,000-metre mark. Originally, this project was aiming to introduce yet another category following the super tall: the mile-high building, but had to be scaled back because the soil would not take the weight.
Aside from the technical challenges, this category of buildings obviously also faces financial challenges. With investments easily going beyond $1bn, super-tall buildings aren’t usually intended to be economically viable as stand-alone buildings but are considered as part of a larger plan, where the signature tower adds value to a surrounding entourage of smaller, more efficient structures.
The challenges these super-tall buildings face are plentiful, requiring enormous financial resources, sophisticated engineering skills, a consolidated will amongst all parties involved to make it happen and finally people willing to work, live, use and pay for them on a daily basis. The sheer size of such projects calls for the right mix of functions that can be economically viable within such a structure, while the overall efficiency of the building suffers from a large core necessary to provide sufficient space for vertical transportation. Traditionally, the elevators needed to whisk us to the top of our towers require heavy cables to work properly; something which adds considerably to the building’s weight.
This summer, Finnish liftmaker Kone unveiled a new design – the Kone Ultrarope – which will shave some 60% off the weight of the elevator infrastructure, such as cables. Seeing as this has been one of the major factors standing in the way of ultra-high towers, plans that were once considered unfeasible because of weight issues may now see the light of day.
The sheer size of these projects, both in terms of floor space and the many thousands of people using them each day, pushing them further away from being seen as buildings and towards new territories; city within a city, a vertical city.
The super-tall towers don’t typically represent companies and are no longer mono-functional. Instead, they are frequently named after the location they represent and come closer to the idea of a vertical city where multitudes of functions are combined under one “roof”. Super-tall building includes offices, hotels, apartments, retail, entertainment and cultural venues. Hotels and apartments at a high location within the building provide magnificent views, but proximity to the ground has its logistic advantages too. Consequently hotels and residential units can be found both at high and low segments. Subway stations allow retail and other commercial elements to find their place in the basement and first few levels above ground, typically within a podium structure.
While this is a rather typical mix for super-tall towers to date, it’s reasonable to think ahead of what else might be part of the functions of towers in the future. Given mankind’s increasing urbanisation, the current division of city and agricultural land is challenged and urban farming is becoming more widespread. It is not a great leap to imagine the towers or tomorrow also being used to grow food; the super-tall towers we see being built today are more likely to have recreational green spaces at first. But the introduction of “vertical farms” may not be far away.
In Japan, where urban density is an increasingly serious problem, two major construction companies, Takenaka and Shimizu, designed concepts for such super cities in the skies many years ago. Takenaka developed a design for Sky City 1000 as early as in 1989. This kilometre-tall structure subdivides the high-rise into 14 horizontal segments, labeled “space plateaus”, comprising a circular ring of apartments or offices surrounding a courtyard with a shared public park in the sky. For ventilation and daylight the individual segments are detached from each other, allowing for an exterior type of climate in the internal courtyards, rain included. The project envisions space for 36,000 inhabitants and 100,000 workspaces within a building of 400m width and with approximately and eight square kilometers of useable space.
Shimizu’s approached the task of designing a building for a large population by proposing a pyramidal structure rising up to approximately two kilometres. Designed for 240,000 residential units and 2400 hectare of office space it can house an estimated population of a million people. The pyramid is essentially a mega truss providing both the structural and infrastructural backbone for a cluster of smaller pyramid cities.
What matters in both projects is not their absolute height. It is the way both deal with the challenge of very large floor area and population by subdividing the design into almost independent units but very well connected amongst each other. In the same time, they attempt to create a sense of human scale up in the air, a relationship to the traditional city with streets and squares in-between measurable built volumes. This urban quality is also claimed by the Shanghai Tower, which refers back to the city’s narrow streets and courtyards by creating sky gardens between the outer and inner skin of the double facade. It remains to be seen if the spatial quality of these spaces can live up to their promise in the end.
Grey water recycling, smart shading and window coatings to reduce heat load within the building, heat exchangers in air-conditioning systems, pre-warming or cooling through ground pipes – these are some of the ideas which could help these new structures limit their effects on the environment. Too big and dominant to become a failure and to be abandoned, the investment should aim for designs that add a public and more urban level to it. These buildings should be designed to be robust and flexible, and should create urban and human spaces at high levels, ones that people could relate to and which can be used in the most mundane ways – like walking our dogs, hundreds of metres above the city streets.
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