.webp)
5 Minutes
A passive cooling breakthrough
When outdoor temperatures rise, most people turn up air conditioning—an effective but energy-intensive response. Researchers led by Wei She at Southeast University in China have developed a new cement that passively cools building surfaces, potentially reducing reliance on mechanical cooling. Their findings, published in Science Advances, describe a cement formulated to reflect incoming sunlight and emit heat as infrared radiation, keeping roofs and walls cooler than ambient air.
How the material works: reflection and thermal emission
Traditional cement readily absorbs solar infrared radiation and stores that energy as heat, warming interior spaces. To reverse that behavior, the research team redesigned cement chemistry and microstructure. They seeded the surface with nanoscale, highly reflective crystals of the mineral ettringite. These crystals increase solar reflectance—acting like a mirror for sunlight—while enhancing thermal emission in the mid-infrared, so the surface can radiate heat away effectively.
The material is produced from common cement components. The team ground pellets made of limestone, gypsum and related minerals into a fine powder, mixed the powder with water, and cast the paste into a perforated silicon mold. The holes in the mold formed micro-depressions where ettringite crystals grew during curing, producing a textured surface optimized for both reflecting sunlight and emitting thermal radiation. The authors describe the final product as functioning simultaneously as a mirror and a radiator.
Field testing and performance
The supercool cement was field-tested on a rooftop at Purdue University. Under strong midday sun, the cement surface measured 5.4 degrees Celsius lower than the surrounding air—an important demonstration of passive cooling under real-world conditions. In addition to optical performance, the material underwent mechanical, environmental and optical durability tests to assess its suitability for construction applications.
Peeling off the recycle and reusable PDMS foil from super-cool cement surface. Credit: Science Advances (2025). DOI: 10.1126/sciadv.adv2820
A direct solidification time test. It showed the fast-setting designability of super-cool cement, which can't be directly evaluated by traditional Vicat Needle Test. Within just 6 minutes after hydration, the super-cool cement had developed enough stiffness to withstand the impact of a 200g iron ball dropping, resulting in only a small pit. Credit: Science Advances (2025). DOI: 10.1126/sciadv.adv2820
.avif)
Environmental and industry implications
Beyond immediate cooling, the team evaluated lifecycle and climate impacts using machine learning. Their analysis indicates the material could achieve a net-negative carbon footprint over a 70-year building lifetime—assuming large-scale adoption and realistic manufacturing scenarios. This arises from reduced operational energy demand (less air conditioning) combined with the cement’s potential to be manufactured with modest changes to existing production processes.
"We have innovatively transformed cement materials from heat absorbers to heat reflectors using a bottom-up approach," the researchers write. "This breakthrough holds the potential to turn the heavy cement industry into a negative-carbon emission system, where supercool cement could play a key role in driving an energy-efficient, carbon-free future for the construction industry."
Buildings account for roughly 40% of global energy use and about 36% of carbon emissions. If supercool cement can be scaled and deployed at scale, the technology could reduce urban heat, lower electricity demand, and cut emissions from cooling—particularly valuable in hot climates and dense cities where air conditioning drives peak demand.
Related technologies and future prospects
Supercool cement complements other passive cooling strategies such as reflective roofing membranes, cool paints, and radiative cooling coatings that emit heat to the sky. Integration into structural concrete, roof tiles, or cladding could allow widespread deployment without major changes to building design. Key next steps include scaling manufacturing methods, long-term weathering tests in diverse climates, and compatibility trials with reinforcement and waterproofing systems.
Expert Insight
Dr. Leila Moreno, a materials scientist specializing in sustainable building systems, comments: "This work is notable because it uses common cement chemistry and a clever microstructural approach to achieve radiative cooling. The 5.4°C surface cooling in field tests is compelling—if the performance holds across seasons and installations, it could become a low-cost, low-maintenance tool for cutting cooling loads. The main challenges will be verifying durability and ensuring manufacturing can be adopted by the cement industry without large emissions or cost penalties."
Conclusion
Supercool cement represents a promising step toward passive cooling in the built environment. By combining reflective ettringite crystals with designed surface topography, the material reflects sunlight and radiates heat to remain below ambient temperature. If scalable and durable, this innovation could reduce air-conditioning demand, lower urban heat, and contribute to decarbonizing a carbon-intensive building sector. Ongoing tests and commercialization efforts will determine whether this laboratory-to-rooftop solution can be adopted widely to help cities and buildings stay cooler with less energy.
Comments