How Do Radiative Cooling Materials Keep Buildings Cool Without Electricity?

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Hot buildings usually need air conditioning, fans or other mechanical systems to remove heat. But a different approach is attracting growing attention: materials that can cool surfaces by sending heat directly toward space without consuming electricity. This technology is called passive radiative cooling, and recent advances are making it more practical for buildings, roofs and other applications.

What Is Radiative Cooling?

Radiative cooling is a natural process in which a surface loses heat by emitting infrared radiation. Special materials are designed to reflect most incoming sunlight while releasing thermal radiation through a part of the atmosphere known as the 8 to 13 micrometre atmospheric window. Because some infrared radiation can pass through this window and escape toward the extremely cold environment of space, the surface can become cooler than the surrounding air.

The key difference is that the material does not need a compressor, refrigerant or electric motor to produce this cooling effect. Instead, scientists engineer the material's optical properties so it absorbs as little solar energy as possible and emits heat efficiently in the relevant infrared wavelengths. Depending on the design and weather conditions, this can allow a surface to reach temperatures below the surrounding air.

How Do Radiative Cooling Materials Work?

A typical radiative cooling surface performs two important jobs at the same time. First, it reflects a large proportion of sunlight so that solar radiation does not heat the building surface. Second, it emits the surface's thermal energy as infrared radiation that can escape through the atmospheric window toward space.

Scientists can create this effect using different materials and structures, including specialised paints, polymer films, coatings, porous materials and engineered surfaces. Some designs use microscopic structures that scatter sunlight, while others are engineered to have high infrared emissivity. Research published in 2026 also shows continuing efforts to develop stronger, recyclable and scalable radiative cooling materials for real-world applications.

Can Radiative Cooling Work During the Day?

Yes, although daytime cooling is more difficult than nighttime cooling. A daytime radiative cooling material must reject the intense energy arriving from the Sun while still emitting enough infrared radiation to lose heat. That is why researchers place such strong emphasis on high solar reflectance combined with carefully controlled infrared emission.

Recent research demonstrates how far the technology has developed. In a 2026 study, researchers reported a wood-derived radiative cooling biocomposite that achieved a measured cooling power of 106 watts per square metre and produced an 8.8°C temperature reduction below ambient conditions during outdoor daytime testing under strong sunlight. Such results are promising, but laboratory or field-test performance should not be interpreted as a guarantee that every building will achieve the same temperature reduction.

Where Can Radiative Cooling Materials Be Used?

Buildings are one of the most important potential applications because roofs and exterior surfaces can receive large amounts of solar radiation. Radiative cooling materials can be incorporated into roof coatings, building envelopes, windows, films and other surfaces to reduce heat entering buildings. They are also being investigated for applications involving solar panels, electronics, textiles, power infrastructure and water harvesting.

The technology could become particularly valuable as cooling demand increases with rising temperatures. A 2026 review in Nature Reviews Clean Technology notes that passive cooling approaches can reduce cooling-related energy consumption, although their effectiveness depends on factors such as climate, timing and atmospheric conditions. This makes radiative cooling potentially useful as part of a broader building-cooling strategy rather than a universal replacement for air conditioning.

Why Does Weather Matter?

Radiative cooling works best when the atmosphere allows thermal radiation to escape efficiently. Clouds can block or absorb some of the outgoing infrared radiation, while high humidity can reduce the effectiveness of the atmospheric window. Researchers therefore continue to study how radiative cooling materials perform under different climates and real-world weather conditions.

This limitation is especially important in hot and humid regions. A material that performs extremely well under clear, dry conditions may produce less cooling under cloudy or humid skies. Future systems may therefore combine radiative cooling with other passive methods, such as shading, ventilation, reflective surfaces and evaporative cooling.

Can Radiative Cooling Replace Air Conditioning?

Radiative cooling is unlikely to eliminate air conditioning everywhere, but it could reduce how much mechanical cooling buildings require. A roof or exterior coating that prevents heat from accumulating can lower the thermal load that an air-conditioning system must remove. That could reduce electricity consumption while also helping buildings remain more comfortable during periods of extreme heat.

The bigger opportunity is combining passive radiative cooling with other energy-efficient building technologies. Instead of depending entirely on electricity to fight heat after it enters a building, designers can reduce solar heat gain and release some thermal energy before it becomes an indoor cooling problem. This approach could become increasingly important as cities face hotter temperatures, higher cooling demand and pressure on electricity networks.

What Is the Future of Radiative Cooling?

Radiative cooling is moving beyond an interesting physics concept toward practical materials that can be manufactured, installed and tested in real environments. Researchers are now working on durability, affordability, colour, mechanical strength, scalability and performance under changing weather conditions. A 2026 review also highlights the need for better evaluation methods because different radiative cooling materials can be difficult to compare consistently.

The most promising future may not be a single miracle coating, but buildings designed around several passive cooling techniques working together. Radiative cooling materials could help roofs and exterior surfaces reject heat, while insulation, shading, ventilation and efficient cooling systems handle the remaining thermal load. As research continues, the technology could offer a practical way to cool parts of the built environment while using little or no electricity.

Read More: What Is Everything-to-Grid Energy and How Could It Change the Power Grid?

Conclusion

Radiative cooling materials work by reflecting solar energy and sending thermal radiation through the atmosphere toward space. They can cool surfaces without compressors, refrigerants or direct electricity consumption, although weather and material performance strongly affect the results. As researchers develop stronger, cheaper and more durable materials, passive radiative cooling could become an important part of how buildings manage heat in a warming world.

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