Researchers discover the whitest white – new color acts like air conditioning

In southern countries such as Greece or Morocco, it is noticeable that many houses are painted exclusively in light colors or completely white. The reason is simple: While dark colors absorb heat and sun rays, white color reflects them. For the people of Greece and Morocco this has the pleasant result that their roofs and house walls do not heat up any more in the heat and sunshine like dark surfaces.

Despite this, the white paints available so far only reflect 80 to 90 percent of sunlight and also absorb ultraviolet light — meaning they heat up to a limited extent. Researchers at the American Purdue University in West Lafayette therefore developed the “whitest color” in the world, which reflects more than 98 percent of incoming sunlight. Painting houses with this color can lower the indoor temperature by 4.5 degrees. This even reduces the use of energy-intensive air conditioning systems.

The only problem so far: To make the surfaces cooler than the ambient temperature, the scientists had to apply the original paint in a 0.4 millimeter thick layer. For permanent structures such as roofs, however, for cars, trains and airplanes, the paint must be applied much thinner, to keep the air resistance as low as possible.

Now the same research team has developed a new formula of the white color with a lighter layer thickness of only 0.15 millimeters. This can scatter sunlight particularly strongly and also has a lower density than before.

The new color can therefore also be used on cars, trains and airplanes and cools the interior. This not only saves money by reducing the need for air conditioning, but also reduces energy requirements – and thus greenhouse gas emissions.

Study leader Xiulin Ruan emphasizes: «Unlike other cooling methods, this paint radiates all the heat into the room, which also directly cools our planet.”

The color is not yet on the market, because it has yet to be clarified whether the nanoparticles in the color may be harmful to people and the environment. But once that is clear, nothing stands in the way of using the color.