Staying cool is one of the most energy-intensive things that our buildings are tasked to do. On a hot day, which there seems to be a lot more lately, buildings get heated by the outside air as well as the sun. That means that in order to stay cool, the outsides of buildings, particularly the roofs which are in direct sunlight, need to be not only good at reflecting the warming UV rays of the sun but also be able to dissipate heat into the air around it.
Creating a material that can do both of those things, as well as be resilient enough to be exposed to the elements for decades without needing to be replaced, has eluded the scientific community for some time. But last week a paper was published in Science that shows a breakthrough in material science that could help buildings be much more energy efficient.
A team from the City University of Hong Kong has used a composite of silica and alumina to create what they are calling cooling ceramic. By mimicking the whiteness of a Cyphochilus beetle, the team was able to create a material that reflects a record 99.6 percent of light. It also gives off heat in a long wavelength form that is not easily reabsorbed or reflected back. The ceramic is made of easily available materials, easy to produce, weather-resistant, and fireproof up to 1,000 °C. It also prevents “The Leidenfrost effect,” a phenomenon where water forms a vapor barrier around a hot surface, thereby preventing its ability to transfer heat.
There have been a lot of attempts to reflect the sun away from roofs in order to lower the energy needed to cool a building, often by applying white paint. But this ceramic seems to be much more effective. One of the researchers predicted a significant reduction in cooling when the material was used for a roof: “Our experiment found that applying the cooling ceramic on a house roof can achieve more than 20 percent electricity for space cooling, which confirms the great potential of cooling ceramic in reducing people’s reliance on traditional active cooling strategies and provides a sustainable solution for avoiding electricity grid overload, greenhouse gas emissions and urban heat islands.”
There is still a long way to go between this scientific discovery and being able to purchase roofing made with this material. But if it works as well as its creators suggest, the development and production of cooling ceramics will be fast-tracked and the adoption rapid. Before long, we might think back to a time when roofs would heat buildings up rather than cool them down.
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