Microclimates - MAGAZINE BY VELUX

		Can architects change the weather? By the year 2100, the world will be at least two degrees warmer than today. Add to this the effect of the ‘urban heat island effect’, with city centres being several degrees hotter than their rural hinterlands, and it becomes evident that city planning has to devise new methods to cope with overheating. A new approach is called for – one that not only considers the thermal conditions inside buildings, but also the urban climate as a whole. By Peter Andreas Sattrup Why? The extreme heat-wave in the summer of 2003 was only a foretaste of the weather events that will be experiencing increasingly frequently in European cities in the future. The fact is that temperatures are going to rise all over the world – by at least two degrees by 2100. Cities are disproportionately affected by this: their usually dark surfaces store heat, and there are often no green areas and corridors to enable air to circulate.

And of course the waste heat from people, buildings, cars and industrial plant also contribute to the fact that cities warm up much more than the surrounding areas.

What?
Cities contribute to climate change, but they are also affected by it to a considerable extent. The heat island effect is responsible for urban areas getting up to ten degrees warmer than the surrounding countryside, and not just in southern climes. Heat is literally ‘held captive’ in the canyons between the tall buildings. There is no evaporative vapour to alleviate the heat – there are two few plants in our cities, and rainwater is taken away in the sewers, rather than being stored in the ground.

How?
Climatic comfort will also become a key feature of town planning in future. Urban climates have to be planned in just the same way as interior air conditioning: cities cannot be artificially ‘cooled down’ from the heat island. Using a mix of lo-tech solutions (vegetation, shading, openable windows etc) and renewable energy sources for cooling purposes is a strategy crucial to handling summer overheating. Above all, the structures of buildings and cities must be much more thoroughly adapted to local climatic conditions (that are also getting warmer).

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