Researchers at Singapore Nanyang Technological University (NTU) have developed a cement based cooling paint that mimics the way human skin cools through sweating. In experiments, a model house coated with the paint remained more than 4.5°C cooler than one covered with conventional white paint.
The paint known as CCP-30 is designed to work through three cooling mechanisms reflecting sunlight, releasing heat as infrared radiation and evaporating stored water. The research was published in the journal Science in June.
Unlike conventional reflective paints, which mainly rely on bouncing sunlight away, CCP-30 uses moisture to remove additional heat. Its porous structure contains calcium silicate hydrate, a cement like material that can absorb and hold water. As the trapped moisture evaporates it carries heat away from the surface.
According to the research, CCP-30 can reflect around 88% to 92% of incoming sunlight and emit nearly 95% of absorbed energy as infrared radiation even when wet. The material can also hold water equivalent to about 30% of its own weight.
Researchers tested the paint on small model houses in Singapore alongside conventional white paint and a commercial cooling coating. The models were exposed to Singapore’s tropical weather for two years. The CCP-30 coated house consistently recorded the lowest temperatures and remained nearly 4.5°C cooler than the other models.
The paint also showed greater durability during the testing period. While the conventional and commercial coatings became noticeably yellowed after two years, CCP-30 remained white. Researchers attributed this to components designed to maintain the coating’l reflective and mechanical properties.
Moisture is central to the paint performance. Instead of being a disadvantage during rainy weather, rain and atmospheric humidity can replenish the water stored in the coating. When sunlight returns the stored moisture can evaporate and provide additional cooling.
The technology could be particularly useful in hot and humid cities where some conventional passive cooling approaches become less effective. By reducing the temperature of building surfaces, such coatings could potentially lower the need for air conditioning and ease pressure on electricity systems.
However, CCP-30 is still an emerging technology. The experiments were conducted on small model structures rather than full sized residential or commercial buildings, and questions remain about large-scale application, cost and availability.
The researchers have reportedly established a company to commercialise the technology. CCP-30 is also distinct from another reflective cooling coating developed at NTU that is being considered for wider use in Singapore’s public housing.
As global temperatures rise and demand for space cooling increases technologies that can passively reduce building temperatures could become an important part of efforts to make cities more energy efficient and resilient to heat.