Researchers from University College London have found that applying a certain type of paint to roofs can mitigate the heat in cities.
It is a white or light-reflective paint — and if this practice was applied throughout the city, its overall temperature could be reduced by 2℃ and reduce the number of air conditioning systems used inside buildings to keep them cool and vice versa increase the temperature outside.
The researchers created a three-dimensional climate model of London based on the two hottest days in the city’s history to evaluate the most effective temperature management system: painted cool roofs, green roofs, woody vegetation on the streets, or air conditioning.
It turned out that air conditioning heated the city center by at least 1℃, while the impact of green roofs varied throughout the day — during the day, the temperature dropped by 0.5℃, but at night, the heat trapped in the organic matter caused the temperature to rise.
Similarly, the planting of deciduous trees helped to overcome the heat at night, but did not provide encouraging results during the day as humidity levels increased.
At the same time, the cold roofs, which reflect rather than absorb heat, balanced the temperature inside and outside, and reduced the temperature by up to 2℃ in certain areas.
«We found that cold roofs — are the best way to keep temperatures low on extremely hot summer days. Other methods had a number of important side effects and benefits, but none were able to reduce urban heat outside to nearly the same level»,” said lead author Oscar Brus in press release.
The study was published in Geophysical Researcher Letters July 4.