Hot in the city: research published on building and city design

Britain is sweltering under the longest heatwave for seven years, with the Met Office declaring a ‘level three’ heatwave warning for London and the South East. For those especially vulnerable, living in a large urban area such as London can make it even more difficult to escape the heat. This is because the design of buildings and the size of built up areas and spaces directly affects urban temperature, wind, rain and air quality – which in turn influence human comfort and health. New ESRC-funded research highlights the importance of designing our buildings and cities with an awareness of the atmospheric effects they are creating, thus protecting us from future heatwaves.

Buildings trap radiation and disturb the airflow of the winds. Impermeable city surfaces repel moisture, whilst dense construction materials store heat. Machine and human activity adds warmth, dust and pollution, whilst air-conditioning for indoor comfort boosts outdoor temperature levels. While the countryside freely radiates its daily heat after dusk, urban surfaces retain heat long into the night, leading to what is called an ‘urban heat island’. The difference between urban and rural temperatures can reach 10?C.

But if cities create their own complex climates they can also shape them. Urban climatology, the branch of science specialising in cities and their weather patterns, clearly shows that design can make a difference. This interaction between city-building, climate and science is the topic of the ESRC-funded study Climate Science in Urban Design.

Covering the period since 1950, the researchers show how the science has leaped ahead thanks to computerisation, mathematical modelling and new technologies of observation.

The study shows how certain cities, particularly in Germany, have worked with scientists to minimise the effects of the urban heat island by careful analysis and mapping of local climate patterns, followed by specific measures to ensure shade in street canyons, cool the air with vegetation and porous paving, or align buildings and open spaces so land and sea breezes can flow freely for ventilation.

However the authors of the study, Professor Michael Hebbert and Dr Vladimir Jankovic from the University of Manchester found that despite all the technology available to them, most planners build cities without an awareness of the atmospheric effects they are creating.

“The need for this awareness will increase as the effects of global climate change become more pronounced, bringing more extreme fluctuations of temperature, and risks of flooding not only from rivers and rising sea level, but also from downpours that overwhelm urban storm drains and sewers,”

says Professor Michael Hebbert.

“Cities which understand and manage their local climate have a head start in responding to global climate change.”