On a hot afternoon in Southeast Asia, a parked car can become almost unbearable within minutes. In some cases, the cabin temperature can climb to 70 to 90 degrees Celsius, turning the first blast of air-conditioning into a survival reflex rather than a comfort choice.
But air-conditioning carries its own contradiction. It cools the inside of a vehicle, home, mall, or factory, while releasing heat outside and drawing heavily on electricity. In cities from Singapore and Bangkok to Manila, Jakarta, and Ho Chi Minh City, this cycle worsens peak power demand and adds to the urban heat island effect, where concrete, asphalt, and glass trap heat long after sunset.
Korean deep-tech startup ZERC believes part of the answer could be as simple as paint.
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Founded in November 2022 as a faculty startup from Korea University, ZERC is commercialising a water-based radiative cooling paint that can be applied to roofs, vehicles, ships, industrial equipment, and even safety helmets. The company was founded by Lee Heon, a professor in Korea University’s Department of Materials Science and Engineering, who has been working on materials that can lower surface temperatures without consuming electricity.
“We founded the company and have continued our research in order to create a practical breakthrough for the climate crisis and energy problems through a technology that lowers temperature without using electricity,” Lee said.
How radiative cooling works
Radiative cooling is not a new idea, but it has become more commercially relevant as global temperatures rise and electricity grids come under strain.
The basic principle is straightforward. A material reflects most incoming sunlight, preventing surfaces from absorbing heat. At the same time, it emits thermal radiation through what scientists call the “atmospheric window”, a range of infrared wavelengths that can pass through the atmosphere and escape into outer space.
In practical terms, the surface cools down without fans, compressors, refrigerants, or electricity.
ZERC says its water-based paint reflects 96 per cent of sunlight when applied at a thickness of 150 micrometres, roughly the thickness of a human hair. It also radiates more than 93 per cent of heat into space through the atmospheric window. In tests, the paint recorded a surface temperature about 4 degrees Celsius lower than ordinary water-based paint.
The company says the cooling effect can last for more than five years and that the initial installation cost can be recovered through electricity savings over one summer season. It also says the paint is resistant to rain, wind, and sunlight, an important requirement if it is to move beyond controlled demonstrations and into construction sites, logistics fleets, factories, and public infrastructure.
For hot and humid Southeast Asia, where cooling is one of the largest drivers of energy consumption, this is the kind of technology that could attract attention from building owners and municipalities. The International Energy Agency has warned that demand for space cooling is growing rapidly, especially in emerging economies. In this region, rising incomes, urbanisation, and more frequent heatwaves are making cooling both a public health issue and an energy security challenge.
Why water-based paint matters
The key claim behind ZERC’s technology is not only that it cools surfaces, but that it does so in a water-based paint format.
According to Lee, paint-based solutions are increasingly seen as more practical than films or panels because they can be applied with rollers or sprays. Films can be difficult to install on curved surfaces, irregular structures, or large areas. Paint, by contrast, fits into existing construction and maintenance workflows.
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The problem is that many radiative cooling paints have relied on organic solvents such as toluene. These solvents make thick paint easier to apply and can reduce costs, but they evaporate during application and drying, releasing volatile organic compounds, or VOCs. VOCs are harmful air pollutants, and some are linked to serious health risks.
ZERC says it has avoided this by developing a proprietary formulation that combines polymers, water, and ceramic pigments instead of toluene. A polymer acts like a binder, helping pigment particles adhere firmly to the painted surface. The ceramic pigments help deliver the optical properties needed for sunlight reflection and thermal radiation.
“Field painting companies are highly sensitive to price and ease of application as well as eco-friendliness, so until now they have used toluene even if it was toxic,” Lee said. “We instead eliminated VOC emissions at the source through a technology that combines polymers, water, and ceramic pigments instead of toluene.”
This distinction may become commercially important. Across Southeast Asia, governments are tightening environmental and workplace safety standards, but construction and industrial maintenance remain highly cost-sensitive sectors. A cooling paint that requires specialised handling, releases hazardous fumes, or disrupts normal application methods would face a harder route to adoption.
From roofs to helmets
ZERC sees applications wherever paint can be used: building exteriors, roofs, vehicles, ships, and industrial equipment. In the tropics, the clearest use case may be roofs. Warehouses, factories, schools, bus depots, and low-rise residential buildings often absorb large amounts of solar heat through rooftops, raising indoor temperatures and increasing the need for mechanical cooling.
Vehicles are another target. Delivery vans, buses, passenger cars, and electric vehicles all face heat-management challenges. For EVs in particular, reducing cabin cooling loads can help preserve battery range, a concern in hot markets.
One more immediate and human use case is worker protection. ZERC is exploring the use of radiative cooling paint on safety helmets for outdoor workers, including those in construction, logistics, ports, and public works.
“If radiative cooling paint is applied to workers’ safety helmets in summer, it can greatly improve thermal comfort,” Lee said. “Workers must wear safety helmets for protection, but this paint can solve the problem of sweat and discomfort inside the helmet. I believe this is one way advanced science can help vulnerable people.”
That point is especially relevant in Southeast Asia, where outdoor workers are increasingly exposed to heat stress. As heatwaves become more frequent, employers and regulators are under pressure to reduce risk without slowing down essential work. Passive cooling tools, if affordable and durable, could become part of a broader worker-safety toolkit.
A growing climate-tech race
ZERC is entering a market that is already attracting startups and large industrial players. Market research firm Spherical Insights projects the radiative cooling market will grow from US$35.8 billion in 2023 to US$87.7 billion in 2033, at an average annual growth rate of more than 9 per cent.
In the US, SkyCool Systems has demonstrated electricity savings by applying radiative cooling panels to supermarket HVAC systems. RadiaCool has worked on lowering cooling loads in electric vehicles. Japan’s SpaceCool has installed cooling film on buildings, including for the Osaka Expo.
These companies show that the sector is moving beyond lab research. But they also highlight the different approaches within radiative cooling: panels, films, coatings, and paints. ZERC’s bet is that a water-based paint can win in settings where low-friction installation, worker safety, and compatibility with existing surfaces matter more than highly engineered hardware.
The startup is also looking at industrial circularity. Lee recently worked with POSCO to develop a radiative cooling paint that recycles slag, a byproduct generated when iron ore is smelted to make iron. If commercialised, that could give the technology another sustainability angle by turning industrial waste into a cooling material.
The larger question is whether ZERC can move from scientific performance to commercial reliability at scale. Paint has to survive weather, pollution, abrasion, uneven application, and years of exposure. Customers will also compare it against ordinary reflective coatings, insulation, roof retrofits, and traditional cooling systems.
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Still, the timing is favourable. In much of Asia, heat is no longer a seasonal inconvenience. It is becoming an infrastructure problem, a labour issue, and a cost burden. If ZERC can prove that its water-based radiative cooling paint performs in real-world conditions, it may find demand not only in Korea, but across the hotter, fast-urbanising markets of Southeast Asia.
As Lee put it, the goal is to move university deep-tech research “beyond papers and patents” and towards real-world problems in industry, energy savings, and carbon reduction. In a warming region, that ambition will be tested not in the lab, but under the sun.
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