Cool roofs could have saved hundreds in London heatwave - study

2018 saw London experience its hottest ever June-August period, with the average temperature of 19.2°C being 1.6°C higher than usual. The new research, conducted by UCL and Exeter University, found that had ‘high-albedo’ cool roofs (roofs painted white or with a reflective coating) been widely installed throughout the capital, it could have cooled the city by about 0.8°C on average. That reduction could have saved the lives of an estimated 249 people – around 32 per cent of the heat-related deaths during that period.

The team also studied the effect that rooftop photovoltaics (RPV) could have had on London temperatures. It was found that wide adoption of rooftop solar would have cooled the city by about 0.3°C, saving an estimated 96 lives. RPV would also have generated as much as 20TWh of electricity during the three-month period, which is more than half of London’s total electricity usage for 2018. The research is published in Nature Cities.

“If widely adopted, cool roofs can significantly reduce the ground-level air temperature of a city,” said lead author Dr Charles Simpson, from UCL’s Bartlett School of Environment, Energy & Resources.

“The resulting cooling effect across the city would save lives and improve the quality of life for residents throughout the urban area. Solar panels have great benefits as a source of renewable power, so it’s good to see they won’t make the city hotter.”

Though seen as unusual at the time, hot summers like the one in 2018 are projected to occur more frequently due to the climate emergency. Urban environments generally absorb a lot of heat and are often a few degrees warmer than the surrounding region - the ‘urban heat island’ effect. The UK is particularly vulnerable to the effect as an estimated 83 per cent of the country's population lives in urban areas.

“The need for our cities to adapt to climate change is clear,” said co-author Professor Tim Taylor of Exeter University. 

“Changing our roof spaces offers one potential solution. We need to encourage action like this, to reduce the burden of excess heat on people living in urban areas and capture potential co-benefits, including energy generation.”