London modelling shows ‘cool roofs’ best at beating heat

Led by Dr Oscar Brousse from UCL’s Bartlett School Environment, Energy & Resources, the study modelled the impact of various cooling approaches for the buildings and streets of London. The team 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. The modelling was based on the two hottest days of the summer of 2018.

It was found that cool roofs could reduce average temperatures across London by 1.2°C, with reductions of up to 2° in some locations. Solar panels and street level vegetation were each found to have an average cooling effect of around 0.3°C, though both of course provide additional environmental benefits. Increasingly popular green roofs - consisting of vegetation that offer benefits like water drainage and wildlife habitats – were found to have a negligible cooling effect on average across the modelled area. The work is published in Geophysical Research Letters.