Researchers at the University of California, Los Angeles have developed a new low-cost method of cooling buildings in the summer and heating them in the winter, using common building materials such as polypropylene, which can effectively manage heat flows between buildings and their environment.
A thermal infrared image of UCLA's Royce Hall shows radiant heat. The facade absorbs heat (white to pale red) from the ground (red color), while some of the ground/building heat is radiated to the cold sky (blue color). Raman Scattering Laboratory/University of California, Los Angeles
This innovative approach is based on the use of common building materials capable of absorbing or radiating heat, which allows for effective indoor temperature regulation without the need for expensive and energy-consuming air conditioning or heating systems. A team of researchers led by Aaswat Raman, an associate professor of materials science and engineering at UCLA, published their findings in the journal Cell Reports Physical Science. A key element of the new approach is the manipulation of radioactive heat — thermal energy carried by electromagnetic waves. Radiant heat affects the temperature of buildings as it travels between objects in the broadband spectrum at ground level and in the narrower infrared spectrum, known as the atmospheric transmission window, between buildings and the sky. This difference in spectra has long been a problem for efficient cooling and heating of buildings, as fewer skyward building surfaces make them vulnerable to heat trapping from the ground and nearby structures. This is especially relevant for buildings in urban environments, where densely built-up areas reduce the possibility of effective cooling due to limited access to the open sky.
Historically, some ancient cities such as Santorini in Greece or Jodhpur in India used white paint on their roofs to reflect sunlight, which helped cool the buildings. However, cooling walls and windows is a more difficult task due to the smaller surface area in contact with the open sky.
In recent years, researchers have made significant progress in using super white paint on roofs, which is able to not only reflect sunlight, but also radiate heat through the atmospheric window. This technology became the basis for a new approach, which involves covering walls and windows with materials that can more effectively manage heat flows.
One of the key materials that the researchers used is polypropylene — widely available household plastic. During experiments, it turned out that this material is capable of selectively emitting or absorbing heat in the infrared spectrum, which makes it ideal for regulating the temperature inside buildings. In addition, polypropylene has high scalability, which allows it to be used in mass construction.
Research has shown that materials capable of effectively radiating radiant heat through an atmospheric window can significantly reduce the surface temperature of buildings in summer and retain heat in winter. This makes it possible to reduce dependence on air conditioners and heaters, which not only saves energy, but also reduces carbon dioxide emissions, contributing to the fight against climate change.
The advantages of the new approach lie not only in energy efficiency, but also in its availability for wide application. The use of cheap and common materials such as polypropylene makes this method cost-effective even for low-income communities, which are often the most affected by extreme weather conditions. This is especially important in the face of global warming, where the need for affordable and sustainable temperature control solutions is becoming increasingly urgent.
Raman's team is now working to scale this technology to large buildings and areas that are most vulnerable to heat, such as Southern California. The researchers plan to demonstrate the effect on large facilities, as well as to calculate the real energy savings that can be achieved by using their approach.
In the opinion of the authors, the proposed methodology has great potential to change the approach to the construction and operation of buildings. in conditions of climate change. It can become an important tool in the fight against climate change and ensure energy efficiency at the global level.