Cooling fabric reduces heat transfer from pavements and buildings in urban areas with high temperatures

In the future, city dwellers could beat the heat with clothes made from new fabrics that keep them cool.

Made from plastic material and silver nanowires, the fabric is designed to keep you cool in urban environments by using the principle of radiative cooling, a natural process in which objects radiate heat back into space.

The material selectively emits a narrow band of infrared light that allows it to escape the Earth’s atmosphere, while at the same time blocking radiation from the sun and from surrounding structures.

Jo Bo-jun, a researcher from the University of Chicago, Illinois, and his team say the material “is more than half [the radiation]” from buildings and the ground,” he says.

Some cooling fabrics and building materials already use this radiative cooling principle, but most of their designs don’t take into account radiation from the sun or infrared radiation from structures like buildings and pavements, and they assume the materials are oriented horizontally against the sky, like roof panels, rather than vertically like clothing worn by a person.

Such designs “work well when they face something cooler, like the sky or a field,” Su says, “but not when they face an urban heat island.”

Xu and his colleagues designed a three-layered fabric: the inner layer is made from common clothing fabrics like wool or cotton, and the middle layer is made up of silver nanowires that reflect most of the radiation.

The top layer is made of a plastic material called polymethylpentene, which does not absorb or reflect most wavelengths and emits a narrow band of infrared light.

In outdoor tests, the fabric remained 8.9°C (16°F) cooler than regular silk fabric and 2.3°C (4.1°F) cooler than a broad-spectrum radiation-emitting material. When tested against the skin, the fabric was 1.8°C (3.2°F) cooler than cotton fabric.

Su said this slight difference in temperature could theoretically increase the amount of time a person can comfortably be exposed to heat by up to a third, but that this has yet to be tested.

“It’s always been difficult to make this material practical as a fiber.” Aswath Raman, the UCLA researcher added that the study is a good example of applying the physical principles of radiative cooling to a practical material. Other materials with similar properties could also be used on vertical surfaces in buildings, he said.