Building density does not necessarily make cities warmer

Building density does not necessarily make cities warmer Keystone-SDA

High-density building does not necessarily lead to more heat in cities. What matters is how the spaces are organised, says a researcher at the Swiss Federal Institute of Technology Zurich (ETH).

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“Densely built-up neighbourhoods with well-placed greenery and lots of trees – as in some areas of Geneva – can be more pleasant than open but less shady and poorly ventilated settlements such as Schönberg in Freiburg,” writes Jan Carmeliet, professor of building physics, in an article published by the university on Thursday.

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In the past, densification too often meant more living space at the expense of green space, which reduced thermal comfort and increased the risk of heat stress, Carmeliet says. It is therefore widely believed among urban planners, authorities and researchers that urban densification inevitably leads to higher temperatures.

“I myself conduct research on heat reduction in cities and I think this assumption is wrong,” he adds. “The problem is not density itself, but how we organise it.” In his view, thermal comfort is created through the interaction between the shade provided by buildings and trees, free ventilation and the cooling of vegetation. This interaction requires an integrated approach that takes into account the needs of each neighbourhood, the local climate and the available space and resources.

Densification is necessary to save scarce land. But it must not be at the expense of quality of life. If we build cities that not only offer more living space, but also more shade, air, green space and nature, then densification is not a step backwards, but a sensible key to a climate-resilient future, Carmeliet concludes.

As part of the SWICE project – sponsored by a promotion programme of the Swiss Federal Office of Energy (SFOE) – the heat load of the neighbourhoods of Geneva and Fribourg was analysed and how different greening and densification scenarios affect comfort.

The project comprises six Living Labs, where researchers work together with residents, authorities, property managers and urban planners to develop and test strategies to combat urban heat.

Translated from Italian by DeepL/mga

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