Although they are a sight to behold, it is not only aesthetics which led the houses of the Cyclades, Andalusia and North Africa to be painted white: it was done to keep them cool! In many developing countries where air conditioning is too expensive, people paint the roofs white in order to reflect sunlight and keep the buildings cool: a method known as passive daytime radiative cooling (PDRC).
With rising temperatures and heat waves occurring around the world, research into innovative, affordable and non-polluting habitat cooling solutions is crucial.
An intelligent and affordable coating which can be applied to almost all surfaces, and which does not consume energy or cause any CO2 emissions
This is what a team of researchers at the University of Columbia (USA) seem to have found when they developed a revolutionary coating that keeps walls at a temperature 6°C cooler than the ambient temperature during a heatwave. The solution consisting of painting buildings’ walls in white is fairly effective as regards visible light, it is not as effective with regard to the UV rays and near infrared rays that also heat up buildings. The researchers found a method that traps air bubbles in a polymer, enabling it to reflect almost all solar radiation. The reflected and radiative solar heat becomes higher than that from the sky, and the surface coated in the polymer becomes cooler.
“It acts along the same principle as snow”, explained Yuan Yang, assistant professor of materials science and engineering at Columbia. “Snow is filled with micron-sized ice crystals that create tiny air voids that scatter light – an effect that makes snow white, rather than transparent like ice, and highly reflective. The researchers created a polymer coating that also contains air voids at the nanometric or micrometric scale and which make it white. “Our coating can be much more reflective than ordinary coatings,” he said.
Polymers for cooling homes more effectively
In addition, although the scientists used a specific polymer, a wide range of other polymers could be used to ensure greater biocompatibility. “The time has come to develop promising and effective solutions,” said Yuan Yang. It is now crucial to develop solutions to this climate issue and we are delighted to be working on this new technology.”