Sustainable and climate-resilient buildings are increasingly adopting passive cooling principles, reducing electricity consumption and relying on conventional cooling systems only when necessary. Researchers from Zhengzhou University in China and the University of South Australia have developed an innovative solution of this kind—a bioplastic cooling metafilm (BPCM).
Thanks to its thin, lightweight structure and ease of installation, the film can be easily adapted to various surfaces – from roofs and façades to integration into building materials. Although such innovations are often associated with new construction, their characteristics can also be highly beneficial for older buildings, where extensive construction work is difficult or not cost-effective. In addition to cooling, the film reduces the load on the power grid during hot months, which is essential for preventing power shortages and mitigating the urban heat island effect, when buildings further heat up cities.
An additional value of the film lies in its biodegradable material, which makes it environmentally friendly and helps reduce plastic pollution, as it contains no petroleum-based plastics. The film is made from biodegradable PLA (polylactic acid) derived from renewable sources such as corn starch. It is specially engineered to contain microscopic crystals and pores that help reflect sunlight and release heat.
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How the Innovation Works
As a passive system, the film does not require electricity to operate – it functions independently. Instead of absorbing sunlight and allowing it to penetrate indoor spaces, the film reflects it back into space, creating a natural cooling effect. The bioplastic film has an exceptional reflectivity of 98.7 percent, meaning it repels most sunlight. In comparison, its high thermal emissivity of 96.6 percent allows accumulated heat to be efficiently released into space, further cooling the building. The microscopic structures within the film enable heat from the building to be emitted as infrared radiation that passes through the atmosphere and is radiated directly into space.
According to a study published in Cell Reports Physical Science, its structure allows buildings to remain up to 9 degrees Celsius cooler than the outside temperature during the hottest part of the day, while the average daily cooling effect ranges from 5 to 6.5 degrees Celsius. Even after prolonged exposure to UV radiation and acids, the film retains its efficiency, making it durable and reliable.
Simulations have shown that the film can reduce annual cooling energy consumption in warm cities by up to 20 percent. Currently, air conditioners and other cooling systems account for about 15 percent of global electricity use and contribute significantly to carbon dioxide emissions so that this innovation could help substantially reduce that impact.
Through this technology, passive cooling is no longer just a scientific experiment – it is becoming a practical solution for everyday life that saves energy, money, and natural resources while making cities more livable.
Although the film is not yet widely commercially available, early adopters in Phoenix and Las Vegas have reported cooling cost reductions of about 15–18 percent during the hottest summer periods. While the film alone cannot fully replace all cooling systems, when combined with renewable energy sources such as rooftop solar panels, it represents a sustainable solution for the future.
Prepared by: Katarina Vuinac
The story was published in Energy portal Magazine GREEN ARCHITECTURE
