Anna Hartz
Reflective roofs could protect cities from extreme heat
Heatwaves are becoming more common across Europe. They are putting pressure on health systems, transport networks, and cities that struggle to cope with extreme temperatures. Scientists say simple changes to buildings and public spaces could help reduce some of the dangers during future heatwaves.
Excess mortality rate at 47.8 percent
Belgium recently experienced its deadliest heatwave since officials began tracking excess deaths in 2000. The country’s public health authority, Sciensano, reported 1,747 more deaths than expected between June 18 and July 1, according to WP. The institute said both the long period of high temperatures and increased ozone pollution contributed to the unusually high number of deaths.
The excess mortality rate reached 47.8 percent across the country. Wallonia was hit the hardest, recording an excess death rate of 76 percent. Brussels reached 60.9 percent, while Flanders recorded 31.4 percent.
The extreme heat also caused problems outside the health sector. In neighboring Poland, railway operator PKP reported that some tracks became deformed after rail temperatures climbed above 70 degrees Celsius. The damage disrupted parts of the railway network.
The deadly heat has renewed interest in ways to keep cities cooler. Researchers from KU Leuven, Sciensano, the VITO research center, and University College London have studied how changes to buildings could reduce temperatures during heatwaves.
Light-colored materials
Their research found that cool roofs could make a significant difference. These roofs use light-colored materials or special coatings that reflect sunlight instead of absorbing it. This keeps both the buildings and the surrounding air cooler.
Researcher Fien Serras from KU Leuven compared the idea to wearing a white T-shirt instead of a black one on a hot sunny day. White clothing reflects more sunlight and stays cooler. She said the same principle works for rooftops across an entire city.
According to the study, using cool roofs on a large scale could lower maximum daytime temperatures in Belgian cities by a little more than two degrees Celsius. The effect would be strongest in densely built urban areas where rooftops cover a large part of the landscape.
Researchers also examined Brussels during the severe heatwave of July 2019. They estimated that 47 deaths during five extremely hot days were linked to the heat. Their study suggests that wider use of cool roofs could have prevented about one quarter of those deaths.
The researchers said the best results come from combining cool roofs with more parks and trees. Roofs reduce daytime heat, while green spaces help cities cool down at night.
