Cool roofs could have saved lives during London’s hottest summer

As many as 249 lives could have been saved in London during the record hot summer of 2018 if the city had widely adopted cool roofs, estimates a new study by researchers from UCL and the University of Exeter.

The document, published in Nature Citiesanalyzed the cooling effect that roofs painted white or other reflective colors would have on London’s ambient temperature between June and August 2018, the city’s hottest summer. From June to August, the average temperature around London was 19.2 degrees Celsius, around 1.6 degrees warmer than the average for this time of year.

Urban environments tend to absorb a lot of heat and are typically a few degrees warmer than the surrounding region, an effect known as an “urban heat island.” Painting roofs white or reflective colors would absorb less radiant energy from the sun than traditional dark roofs, effectively cooling the city.

Researchers found that if light-colored cool roofs had been widely installed across London, they could have cooled the city by around 0.8°C on average, preventing the heat-related deaths of around 249 people. , which is equivalent to approximately 32% of the world’s population. 786 heat-related deaths during this period.

In the same paper, the researchers also found that if rooftop photovoltaic solar panels had been adopted on a large scale, they would have also cooled the city by about 0.3°C. This would have prevented the deaths of about 96 people in the city, or 12% of heat-related deaths during this summer.

The researchers used a complex 3D computer model to simulate the results of different urban environments. They calculated average urban temperatures during the hot summer of 2018 (comparing them to actual measurements at the time), then compared the temperature differences if all roofs in London were given reflective coating, if all Roofs were covered with solar panels. panels and what the temperature would be in a hypothetical non-urbanized London.

The team also estimated the economic impact of increased mortality rates from both scenarios. The 96 lives saved through the adoption of rooftop solar panels would have reduced the city’s economic burden by around £237 million, while the 249 lives saved through the adoption of cool roofs would have reduced the burden city’s economic value of around £615 million.

Furthermore, if rooftop solar panels had been widely installed, the researchers estimate that the total amount of electricity that could have been produced during this three-month period would have reached 20 terawatt hours (TWh), or more than the half of London’s energy consumption in all of 2018.

Lead author Dr Charles Simpson (UCL Bartlett School Environment, Energy & Resources) said: “If widely adopted, cool roofs can significantly reduce the ground level air temperature of a city . The resulting cooling effect throughout the city would save lives and improve the quality of life of residents throughout the urban area. Solar panels have great benefits as a renewable energy source, so it’s good to see that they won’t make the city hotter.

Tackling urban heat is becoming increasingly important as the planet continues to warm due to climate change. Although unusual at the time, hot summers like 2018 are expected to occur more frequently due to global warming. Additionally, the UK is particularly vulnerable to these effects, as an estimated 83% of the country’s population lives in urban areas.

Dr Simpson added: “As the effects of climate change become more evident, city dwellers will need to find new ways to adapt. Our research shows that cool roofs could be an effective way to mitigate the heat-trapping effects of urban temperatures. environments.”

Co-author Professor Tim Taylor, from the University of Exeter, said: “The need for our cities to adapt to climate change is clear. Changing our attic offers a potential solution. We must encourage actions like this, to reduce the burden of excess. heat on people living in urban areas and capture potential co-benefits, including energy production.

Recent preliminary research by team members found that during the three hottest days of 2018, widespread adoption of cool roofs would have lowered the city’s average temperature by around 1.2 degrees Celsius , while rooftop solar panels would have lowered the average temperature by around 0.3 degrees. C. This new research extends these modeling efforts throughout the summer of 2018, the hottest on record in London.