Reflecting the sun’s rays and helping buildings maintain a more comfortable temperature could lead to both energy savings and a better indoor climate.

On a sunny day, buildings absorb a significant amount of solar radiation and heat up quickly. Now, researchers from the USA, China, Singapore, and Sweden have succeeded in creating a range of advanced thin metamaterials that not only block solar radiation but also emit heat, thereby lowering indoor temperatures. One of these materials can be applied like paint—either by spraying or brushing it on.

Metamaterials are artificially engineered materials with properties that surpass those of natural materials. Developing cooling metamaterials has previously been a time-consuming process requiring trial and error. The new method uses machine learning and artificial intelligence to generate thousands of complex structures with the desired properties—reflecting solar radiation and emitting thermal radiation—in just a few days. The most promising candidates are then selected based on how cost-effectively they can be manufactured at scale.

Researchers have used artificial intelligence to develop a paint that can help keep buildings cooler. The method, presented in Nature, could lead to both energy savings and a more comfortable indoor climate. Max Yan, Associate Professor at Umeå University, contributed to the development of the method and the interpretation of the results.

– A roof painted with the specially designed material maintained an indoor temperature that was 5.6 degrees Celsius lower than a similar building painted with conventional white paint, he says.

The new paint can lead to significant energy savings by reducing the need for air conditioning. Calculations show that if the paint is applied to the roof of a typical four-story building in Bangkok, with a roof area of 780 sqm, it could save around 12,000 kilowatt-hours of electricity per year. In countries with cold winters, such as Sweden, the AI-based method can be adapted to design thin materials or paints that instead help retain heat inside buildings.

In addition to buildings, the new paint can also be used on other objects, such as cars, trains, or machinery. The need for efficient cooling is increasing as the climate changes and heatwaves become more frequent and intense.

– This type of material can contribute both to better living environments and significant energy savings, Yan explains.

In the longer term, the technology could even be used to regulate the climate on a global level.

– Will widespread use of this type of cooling metamaterial help slow down global warming? I haven’t spent much time on that question, but I’d say it’s worth exploring, Yan concludes.