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A tale of tall cities

The Council on Tall Buildings and Urban Habitat (CTBUH) will hold it's 8th World Congress in Dubai in March. Conrad Egbert meets up with the executive director of CTBUH, Antony Wood, to ask him where Dubai is headed.


The Chicago-based Council on Tall Buildings and Urban Habitat (CTBUH) is a multi-disciplinary group with a membership of over 7,000 individuals and corporations', consisting of the world's leading architects, engineers, builders and developers, representing more than 77 countries. The Council holds a World Congress every four to five years and, this year, Dubai has been chosen to host its 8th session, running from 3rd to 5th March.

The council's executive director, Antony Wood, talks to Conrad Egbert about sustainability in tall buildings and how Dubai could take the lead in sustainable urban design.

Are tall buildings really sustainable?

Yes they are if you look at the bigger picture. And the bigger picture is about urban sustainability. Just to step out of Dubai for a second - if you look at countries like China and India, you see millions of people moving from rural areas into urban cities. Where do you put all these people?

The technical achievement of the Burj Dubai cannot be overstated. You cannot look at it only from a sustainable point of view.

The American and UK models have been based on suburbia - it's been based on a business core where everybody lives out in suburbia. And that's unsustainable when you think of future cities.

It's unsustainable because of the transport infrastructure, the transport pollution and the energy distribution.

It's all about infrastructure and networks. And so denser cities are the way forward with one of the solutions being vertical cities with tall buildings. On an urban scale that is one of the advantages of tall buildings.

There are other advantages, including financially - professional investment in tall buildings is very significant and that gives an opportunity to invest in sustainable technologies that are perhaps lacking in low-rise buildings that don't have as big budgets.

Wouldn't such large buildings have a destructive effect on the environment?

The way forward for sustainable tall buildings is to link back into the environment.

That was the mistake that happened with modern architecture and tall buildings 50 years ago at the end of World War II.

We created these sealed air-conditioned boxes that no longer needed to relate to the environment. Now these tall buildings have to link back into the environment by using natural energy sources. For example, the efficiency of wind energy is more than directly proportionate to wind velocity and wind velocity increases with height, so wind turbines at the top of a tall building will be far more efficient than ones on a small building. And it's similar with solar panels.

One would think that the height of a building is inversely proportionate to its sustainability levels?

There's an off-setting factor against that as well. There's a high-embodied energy in constructing a tall building. If you build a five-storey building and then you build a 10-storey one or a 15-storey one, you go above a certain height; you might actually get a two story efficiency due to the logistics of getting materials up at that height so there is a high-embodied cost. It is correct but you have to see the bigger picture.

What would you say is the ideal height for a building to remain sustainable?

It's not easy to define that. If you look at most tall buildings now, maybe 300m is seen as a cut-off for super-tall and above that is super tall. I'm not saying that 300m is an ideal height and below that sustainable and above that not, but I think for super tall buildings there are other factors that need to come into it to justify it being super tall.

It might be image or iconography. That's always been a factor in tall buildings - no one needs to be embarrassed about that. You know the history of the world's tallest buildings has very rarely been about creating sustainable buildings.

With the environment becoming such an issue isn't a shift in the focus for tall buildings needed now?

Dubai has a greater opportunity than most cities to lead the world in terms of what can be done. Dubai is doing what other people only talk about. Other cities talk about wanting things to be done but they don't because they have a lack of finance, political will, bureaucracy, or whatever the factors are. They cannot achieve what Dubai has achieved in such a short space of time, so Dubai has an ability or an opportunity to take on board this difficult agenda of leading the way in terms of creating sustainable tall buildings and showing the world the way forward in that.

If you look at the extremes, there are two ways of developing a city. You can either look to build horizontally, which to me is an unsustainable way forward, or you could go to the other extreme, where you create an intense vertical city. There have been proposals for this - for a city in the sky. It's exactly the same as the urban plain except that it's up in the sky. There have been hypothetical proposals for this in Japan in the 1980s.

It's very easy to just look at the embodied energy principal and say well ‘okay maybe above 300m is not sustainable' but I think you've got to look at the bigger picture.

What's the case in Manhattan or Hong Kong? There just isn't the space to go any further. And if you started to recognise that green space or even desert space is precious for whatever reason then there is no more space for horizontal expansion, and then you've got to go vertical.

But Dubai isn't only building super talls; it's also expanding horizontally... so much so that it's even claiming land from the sea. How exactly is that a world-leading example of sustainability?

The only answer I have for that is the one I've given you already. The Burj Dubai is firstly a model for what can be achieved on a small plot of land. If the basic element of sustainability is to reduce the impact on the land physically, then that's the basis for saying that it's a sustainable tower. There are other factors at play here, which include the technical achievements of the tower.

The technical achievement of the Burj Dubai cannot be overstated. You cannot look at it only from a sustainable point of view. It needs to be about the whole city, the whole social structure. You can argue that the Burj Dubai has focused the world's attention so much on Dubai that, that in itself, has drawn attention to the importance of sustainability in buildings. It may not itself be the most sustainable model but just the fact that it is working towards it and it is the Burj Dubai, it has brought the issue of sustainability into the public eye.

The Burj Dubai would have been conceived seven or eight years ago; the gestation period for any tall building is a long period and you cannot judge anything - this is moving so quickly. There has only been a consensus in the last eight months that there is a problem with climate change and we need to do something about it and we are in a very experimental stage. It is very unfair, I think, to look at these projects and rate them by a yard stick that we've just come up with.

Which city do you think has the most sustainable buildings?

Well, I'll probably give you three answers for different reasons.

The opening presentation at this years� Congress in Dubai will discuss three papers on three cities each that have taken sustainability in tall buildings very seriously. Those cities include Chicago, London and Dubai.

I'd say Frankfurt in Germany - because it has one of the buildings that I'd put in the top three sustainable tall buildings in the world - the Commerzbank building in Frankfurt. It's the political structure for why the Commerzbank came about and the sustainable directives that it's had for 20 years.

The second would be London - for the same reason, but more recently. Mayor Livingstone in London has said that all major projects should have 10% of its energy created on site and it's implemented a traffic congestion charge. These are really quite bold moves for a major city to implement.

And thirdly, Chicago, but for different reasons. Fifteen years ago Chicago implemented the policy of green roofs in all our buildings and if you as a developer put a green roof in your building then we'll give you a special channel for planning permission. We'll speed all that up for you; so again political infrastructure for it.

Are green facades in buildings in Dubai feasible?

Completely. Green facades are totally feasible. Why not? If you're going be doing it anywhere, why not in an intense desert climate where there's abundance of sun?

Then why don't we see such an obvious sustainable option in Dubai already?

It's not been high enough on the agenda. These tall buildings that you're seeing here are products of design thinking from six to seven years ago; when it just wasn't part of the mainstream thinking that there is a need to move beyond corporate ego and iconicness. There wasn't this collective consensus that we needed to move beyond that. Now there is but you will not see the fruits of this in tall building form over here or anywhere else for another four or five years and it may actually be another 10 years before we start achieving anything on an urban level and that's just new buildings; what about the existing buildings?

But I think one of the key things for a tall building is the building envelope. If you make it more opaque through less glass or more vegetation it will be more environment friendly. There are buildings in the Middle East that have all solid facades. If you do that there can be a trade-off with natural light. For me, sustainability is not just applying technologies, wind turbines and solar panels and all the rest of it. It's about rethinking the fundamentals of the architecture from day one; the shape of the building, the orientation, where to put the core in the building, to shield the building from bi-solar gain, what to use as the skin of the building, what are the spaces to become, are they just residential or are you creating vertical cities? Should you not then be putting the public infrastructure in to them like schools? Should residential towers just be for the exclusive people who can buy them or should they be for all? Should they have social communal spaces in there like sky gardens? You know this is all part of the package. Not just applying some kit to the building.

Also you've researched the idea of sky bridges in tall buildings to make them more sustainable - could you tell us some more about this?

We discussed the model of the horizontal city, which I think is an unsustainable way forward and most people recognise that.

In the past years various cities with geographical constraint like Manhattan and Hong Kong have gone for vertical cities and denser taller cities so it just seems completely nonsensical to me that the pavement on the ground remains the only plane of horizontal connection. It's inefficient. It means everybody has got to go up and down. In an emergency everyone needs to come down to the ground plain. We need to introduce horizontal connections between buildings at a height. Not abandon the ground plane but recreate the same plane at various levels of height. Once we start to do that, the great height of the Burj Dubai and other projects won't look so unsustainable because you're actually bringing public into it and that would become the zone for the recreation of public facilities that I've been talking about; parks, schools, hospitals and all the important aspects of a true mixed-use city.

There are buildings around the world that do it. You've got the longest sky bridge here in Dubai - The Marriott Apartment towers - and it links in the facilities at the top. Think about the energy savings in that by not having to move everybody up and down by escalators. The benefits of evacuation. The Petronas Towers in Kuala Lumpur have a double storey sky bridge at half height. That's a fire-rated sky bridge. In the event of a fire, half of its population can move across that sky bridge and down through a safe tower.

The designer of those towers was able to omit one fire stair from each of the buildings because of an alternative evacuation route. One fire stair, 3m by 6m, 18m2, per floor times two, times 88 storeys, times two towers; that's a lot of money. It could be put to office use so it has a financial benefit, fire safety and energy efficiency.

But in my book the most important is that it has benefits for urban enrichment. You know it's great to be up there in the sky. The benefits of the Burj Dubai are slightly intangible. What about the benefits in terms of the clarity of air at that height? Okay for those who are lucky enough to live there but what if this was replicated?

You mentioned that developers should be given incentives for sustainable buildings?

Yeah, Chicago will speed up the licensing process if the developer incorporates green roofs in its buildings.

Over here, something similar can be done for the implementation of green facades in buildings or any other defined sustainable move. You could adopt the LEED system here. For example, any building that attains LEED Platinum stage in its design stage can go through an express channel process. It's about encouraging sustainable approaches.

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