A team led by UCLA materials scientists has demonstrated a white paint that can reflect as much as 98 per cent of incoming heat from the sun. If widely applied to rooftops and buildings, the new paint could significantly reduce cooling costs. Air conditioning is both expensive and energy inefficient. A more sustainable method is to cool buildings using passive daytime radiative cooling. This is a process whereby the building’s surface is made reflective, to radiate heat out into space. One method to make surfaces reflective is to paint them white. The researchers showed that the new paint could reflect as much as 98 per cent of incoming radiation. According to Aaswath Raman, the principal investigator on the study, “A roof painted white will be cooler inside than one in a darker shade. But those paints also do something else: they reject heat at infrared wavelengths … [using the new paint] could allow buildings to cool down even more by radiative cooling.”