By reflecting infrared heat, these new paints keep buildings cooler in the summer and warmer in the winter without using energy.
In parts of the world with hot, sunny climates, it's normal to see houses painted white to reflect sunlight in order to stay cooler during the day, like Spain's Pueblos Blancos. But now engineers at Stanford University have added colour to such cooling paints.
The extra good news is that their new paints can be any colour of the rainbow, and can keep buildings cooler in the summer and warmer in the winter, thereby significantly lowering energy use of space cooling and heating systems.
In laboratory experiments, the paints reduced the energy used for heating by about 36 percent and energy needed for cooling by almost 21 percent. That's potentially very good news as heating and cooling homes and buildings accounts for about 13 percent of the world’s energy use. And, as this will help reduce the world's carbon footprint, researchers all over the globe have been developing passive heating and cooling technologies that do not use energy - and this new paint is yet another innovative option.
Paints that reflect heat offer a passive route to cooling not just buildings but also cars and trucks. How do these new paints work? According to the report in the journal Proceedings of the National Academy of Sciences they are composed of two layers. The bottom layer is based on aluminum flakes that reflect infrared radiation, while on top is an ultra-thin layer that lets infrared waves through and contains tiny particles that can be different colours.