Passive cooling paint sweats off heat to deliver 10X cooling and 30% energy savings

A new cement-based paint can cool down the building by sweating off the heat. The cooling paint, named CCP-30, was designed by an international team of researchers and features a nanoparticle-modified porous structure composed of a calcium silicate hydrate (C-S-H) gel network.

This design enabled it to achieve superior cooling by combining both radiative, evaporative and reflective cooling mechanisms, which allowed it to reflect 88–92% of sunlight, emit 95% of the heat as infrared radiation, and hold about 30% of its weight in water, making it a paint ideal for keeping spaces cool throughout the day and across seasons.

As per the findings published in Science, the paint provides 10 times the cooling power of commercial cooling paints in tropical climates, resulting in electricity savings of 30 to 40%.

Space cooling systems take up nearly 20% of the total electricity usage in buildings around the world today, making them a significant contributor to global warming due to high CO₂ emissions. It also plays an important role in driving the urban heat island (UHI) effect, a phenomenon where city centers experience much higher air temperatures than the surrounding suburban areas. Passive cooling strategies have emerged as an energy-efficient and sustainable approach to reducing emissions and urban heat island (UHI) effects.

Most passive cooling paints rely on a radiative mechanism, which leverages the passive cooling process where objects on Earth lose heat to the colder outer space by emitting infrared radiation. This process works wonders in dry climates and under clear skies, but suffers in humid regions with frequent cloud cover. The highly directional nature of this process makes it far less effective on vertical surfaces that aren’t under direct line of sight to the sky.

The researchers were able to overcome these major pain points of the radiative mechanism by harnessing the power of evaporative cooling. By taking advantage of water’s high latent heat (~2256 J/g), evaporative cooling absorbed a significant amount of thermal energy from a surface as the water turns from liquid to vapor. It also provided non-directional cooling, wherein the mechanism was not dependent on factors like surface orientation and restrictive side views.

As a result, the newly designed paint delivered powerful cooling performance, boasting an impressive 95% infrared emittance even under direct sunlight, along with 88–92% solar reflectance in both wet and dry conditions.

What truly set CCP-30 paint apart was its self-replenishing ability—absorbing water from rain and atmospheric moisture to sustain evaporative cooling over time—without compromising how the paint interacts with light when wet.

In field tests conducted in tropical Singapore, CCP-30 outperformed commercial white paints with its exceptional cooling power. Pilot-scale building tests showed 30–40% electricity savings, while life-cycle analysis revealed a 28% lower carbon footprint per functional unit compared to standard white paint.

Apart from offering a practical and long-term solution for mitigating the urban heat island effect, the paint presented itself as an innovative solution with real-world potential to support global decarbonization efforts.

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