Painting roofs white or covering them with a reflective coating would be more effective at cooling cities like London than vegetation-covered “green roofs,” street-level vegetation or solar panels, finds a new study led by UCL researchers.
The research, published in Geophysical Research Letters, used a three-dimensional urban climate model of Greater London to test the thermal effects of different passive and active urban heat management systems, including painted “cool roofs,” rooftop solar panels, green roofs, ground level tree vegetation and air conditioning during the two hottest days of the summer of 2018, the warmest on record. It found that if adopted widely throughout London, cool roofs could reduce outdoor temperatures across the city on average about 1.2 degrees C. Meanwhile, air conditioning, which transfers heat from within buildings to the outside, would warm the outdoor urban environment by about 0.15 degrees C for the city overall, but by as much as 1 degree C in dense central London.
https://www.ucl.ac.uk/news/2024/jul/cool-roofs-are-best-beating-cities-heat