White roofs could be a lifesaver during heatwaves: Study

Roofs painted white or other reflective colors not only look aesthetically pleasing, but could, in fact, be a lifesaver during violent heat waves. A recent study reported that if every household had white roofs (aka cool roofs) and rooftop solar panels, these climate change adaptation tools could have saved an estimated 345 lives in the summer of 2018 in London.

“The built environment of urban areas alters the energy balance of the land surface, resulting in cities having their own climate, different from nearby rural areas. Typically, this leads to higher air temperatures in urban areas, especially at night, known as the urban heat island effect,” the researchers explained. “This is interesting because 83% of the UK population lives in urban areas.”

“The summer (June, July and August) of 2018 was the warmest on record for England, with the average temperature nearly 2 °C higher than the 1981–2010 average in many parts of southern England. The maximum temperature officially recorded was 35.6 °C on July 27,” they noted. “We find that heat-related mortality in this period (estimated 655–920) could have been reduced by 96 (12%) by rooftop PV and 249 (32%) by cool roofs, in scenarios where all roofs have these measures.

The researchers further estimated that solar roofs and cool roofs could have reduced the economic burden of heat-related deaths and lost productivity by up to £237 million and £615 million, respectively.

White roofs keep households and other indoor spaces cool by reflecting sunlight back into space, preventing heat absorption during hot summer days. In fact, if every building in a city had white roofs, it could help cool urban areas by about 0.8 degrees Celsius on average. On the other hand, installing solar panels on the roof of every building can cool a city by 0.3 degrees Celsius.

Study co-author Tim Taylor of the University of Exeter said in a press release: “The need for our cities to adapt to climate change is clear. Changing roof spaces offers us a possible solution. We need to encourage action like this to reduce the burden of excessive heat on people living in urban areas and to harness potential co-benefits, including energy production.”

The researchers used computer climate models to simulate the effectiveness of climate change adaptation solutions such as cool roofs and rooftop solar panels during an unusually hot summer like the one that took place in 2018.

The study’s lead author, Charles Simpson from the UCL Bartlett School Environment, Energy & Resources, said in a press release: “If widely adopted, cool roofs can significantly reduce the air temperature on the ground in a city. The resulting city-wide cooling effect will save lives and improve the quality of life for residents throughout the urban area. “Solar panels have great benefits as a source of renewable energy, so it’s good to see that they won’t make the city any hotter.”

“As the effects of climate change become more pronounced, people living in cities will have 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 environments,” Simpson added. .

The findings of the study were published in Cities of nature on October 1, 2024.