With global energy use expected to almost double by 2050, finding ways to passively keep cool without using energy will be vital in the coming decades. Scientists at Purdue University (US) have developed a light-reflecting “ultra-white” paint which they say could lessen the need for air conditioning, and greatly reduce carbon emissions if used on a massive scale. The paint is capable of reflecting 98% of sunlight and therefore has the ability to actually cool buildings.

White paint has been used for centuries in warmer climates to keep buildings from absorbing too much heat from the sun. However, regular white paint absorbs about 20% of sunlight, whereas the ultra-white paint takes on just 2%. This allows the process of radiative cooling, which makes the temperature on the roof up to 2°C lower than the surrounding air. According to professor Xiulin Ruan, the lead researcher on the project: “If you use this paint to cover a roof area of 100 square metres, we estimate that you would get a cooling power of ten kilowatts. That’s more powerful than the central air conditioners used in most houses.”