As our planet keeps warming, air-conditioning systems are proliferating. While such systems make interior work and living spaces cooler, they add heat to the immediate outside space. Almost every city suffers from the heat island effect, a phenomenon where concrete-abundant environments trap and radiate heat. This released hot air makes neighborhoods hotter, further discouraging people from going outdoors. Space cooling accounts for about 30 percent of total electrical usage worldwide. With increasing temperatures, this number keeps growing, adding more greenhouse-gas emissions and more climate impact.
An international team of scientists in Singapore has recently developed a cement-based paint that mimics our body’s natural cooling mechanism of sweating. Most cooling paints rely on the radiative and reflective properties of white to reflect sunlight and beam heat to the colder outer space by emitting infrared radiation. Such products work well in dry climates with clear skies but falter in humid regions with frequent cloud cover and high humidity. The moisture and blocked skies trap heat and prevent it from escaping. In addition, these paints don’t work well on vertical surfaces, which cannot emit to the overhead skies.
The new paint incorporates passive cooling mechanisms. It combines three forms of passive cooling: radiative cooling, evaporative cooling (like our sweating), and solar reflection. It reflects 88-92 percent of sunlight, even when humidity is high, and emits up to 95 percent of the heat it absorbs.