Flat roofs are very common for residential as well as industrial buildings. The space is used for air condition devices, bars, greens or pools and other demanding purposes. Roof sealing needs to be durable, waterproof and long-term stable. Thus, bituminous materials are one logic solution. But they are black, and black means high absorption rates of infra-red radiation, leading to higher temperatures in the lower levels of the building. White coatings can prevent that, but only if they remain white for as long as possible. Dirt-pick-up and bitumen bleeding can turn a bright white coat into a brownish, relatively dark ...