Cool roof technology in London: An experimental and modelling study

► We studied the energy impact of a cool roof in an office building in London. ► The study includes experiments and thermal modelling. ► Thermal comfort improves by 2.5 °C but heating demand increases by 10%. ► Overall energy demand reduces between 1 and 8.5% relative to an albedo of 0.1. ► Roof reflectivity of 0.6-0.7 is optimum for London climate.