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    5 questions for Arup Fellow Alistair Guthrie on commercial towers and façade design

    Nathan Johnson

    Alistair Guthrie is an Arup Fellow and until recently leader of global sustainability skills at Arup. He is a Professor of Environmental Design in the School of Built Environment Nottingham University. He joined Arup in 1979 and in 1985 opened Arup’s first office in the USA. He has been involved in the design of arts & culture, education, commercial and high-rise buildings worldwide.

    His particular expertise is the application of building physics to find innovative, integrated and sustainable solutions to help create some of the world’s best architecture.

    We caught up with Guthrie while he was in town for The Australian Smart Skyscrapers Summit 2017, to discuss his firsthand experience with the evolution of skyscraper and façade design.

    Throughout your career, you’ve worked with world leading architects on some of the most sophisticated commercial towers ever built. Is there a single highlight and why?

    Shard.jpgEvery tower I’ve worked on has had unique challenges but what I’ve tried to do is to bring the efficiency of the building in terms of energy to the forefront, whilst still trying to realise the architect’s ambition for the project. One project stands out, The Shard in London with architect Renzo Piano (pictured right), where the challenge was to produce an energy-efficient façade, one that not only met the London regulations but was also as energy efficient as it could be.

    The architect had a vision of this ‘shard of glass’ as he called it – a continuous glass surface which looked like a pointed shard of glass, and so I worked with the architect, façade designers and with the system designs, to achieve a very high performance façade using an active façade system, which incorporated automatically controlled roller blinds. We had a very low level of reflectivity on the glass which did exactly what the architect wanted to do, to allow the passing clouds to be seen in the façade.  So to achieve that, and a very efficient façade at the same time, was quite a highlight for me.

    The evolution of façade technology has no doubt been significant since you began at Arup, which do you think has been the most positive technological advancement for commercial tower facades?

    There’s a simple answer to this, and it’s glass technology. The sort of curtain walls that we now achieve like on The Shard - the size of glass, the selective coatings, the multiple glass layers with automatic blind has made a huge difference to both the performance of the façade as well as what it looks like.

    Part of this evolution has spawned out of a quest to maximise glazing without detriment to the environmental performance of a building… do you think this is achievable/has been achieved? Or should we be rethinking glazed commercial towers altogether and focussing our efforts elsewhere?

    As I’ve said earlier, I think that we have achieved considerable advances in the environmental performance of the building with full-glazed facades, The Shard is a good example, and we’ve talked about other buildings in Australia, such as 1 Bligh Street in Sydney, which show composite layers of glazing, glass or blinds, different layers for different functions, and different coatings.  

    We’ve begun to reach the maximum performance of 100 per cent glass facades, so if we want to improve performance beyond what we’ve now achieved, which is a good ambition, then we need to look at composites of other materials with the glass to provide the improved performance. 
     

    If we reduce the glazed area of a façade then we have to be very careful not to affect the benefit of the views and the daylight. But I think it is possible. So moving away from 100 per cent glazed to incorporate other materials in the overall façade will be necessary in the future as we seek to improve the performance further.

    What do you consider the biggest hurdle we have to overcome to improve the environmental footprint of commercial towers? Should we be reducing our reliance on mechanical systems or moving to renewables to reduce their impact?

    We can improve the efficiency of the plant and we do that a lot, we can improve the efficiency of the lighting system and we’ve gone a long way to achieve these goals, but by far the biggest player in the energy consumption of the building is the façade, and improving the façade will have the biggest impact on its environmental performance.

    My view on how we should go about that on our towers is to go away from flat curtain-wall type systems to make way for more shaped façade systems which have much more potential to have better performance characteristics for solar shading. 
     

    If we can maximise the daylighting and minimise the solar gain on these facades by using shaped facades then that would be the way to go. That will automatically reduce our reliance on mechanical systems, as we’ll need less of them, and I also think that in some climates, it will give us the possibility of open facades on our buildings, thereby again reducing the reliance on mechanical systems. 

    I don’t think we should use renewables as excuses to make up for poor design of our buildings. I think that when we get the design right, the facades and the systems, then the renewables that we can use will have a bigger impact. Just putting them there to make up for poor design is definitely the wrong strategy.  

    What commercial façade technology is interesting you most currently?

    The potential for vegetation on the façade of the building in different ways is of interest to me. For example, for the climate and for the type of city landscape in Melbourne, we calculated that green walls could reduce the level of pollution particles in the air in the street canyons by 20 per cent and could also reduce the peak temperature at street level by up to 9.5 degrees centigrade.   

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