Cooling Paints
Cooling paints, also known as heat-reflective paints or thermal barrier coatings, are a remarkable innovation in the world of surface coatings. These paints are specifically formulated with special ingredients and technologies to provide a cooling effect on the surfaces they are applied to by reflecting a significant portion of the sun's heat away from the surface. This is achieved through the inclusion of specialized pigments, additives, or microscopic reflective particles in the paint formulation. These components work together to create a barrier that reflects solar radiation, preventing it from penetrating and heating up the underlying surface. By reducing heat absorption, cooling paints help to maintain lower surface temperatures, even under intense sunlight.
While regular white paints do reflect a lot of visible light, it still absorbs ultra-violet and infra-red rays which warm the surface they are painted on. Since paints and other films and covers that shield surfaces is an effective way to combat a lot of the heat dissipated to the surroundings in urban areas, there has been several efforts already in place to tackle this issue.
Some currently available efforts and technologies are:
Researchers from Columbia University were researching the reflectivity of air voids in plastic and found out about a certain phenomenon in a polymer that forms a number of air pockets in the film when it dries, which very effectively reflects light and heat. They then recreated this idea in other polymers, and managed to create a paint that can be painted or sprayed on surfaces and proved to have kept them cooler by up to 6°C in the heat of Arizona (https://www.science.org/doi/full/10.1126/science.aat9513)(https://www.sciencedirect.com/science/article/pii/S2542435120301793). This paint can also be dyed to make new colors (https://www.science.org/doi/full/10.1126/sciadv.aaz5413).
Radi-cool - Passive radiative cooling requires a material that radiates heat away while allowing solar radiation to pass through. Zhai et al. solve this riddle by constructing a metamaterial composed of a polymer layer embedded with microspheres, backed with a thin layer of silver (see the Perspective by Zhang). The result is an easy-to-manufacture material near the theoretical limit for daytime radiative cooling. The translucent and flexible film can be made in large quantities for a variety of energy technology applications. This is not a paint, but a material of film that can be laid on walls and rooftops which uses passive radiative cooling to dissipate heat from the object it covers, hence cooling the surroundings. Using this can decrease AC use in households.
SkyCool Systems - A team of scientists working to develop different technologies to promote cooling of surfaces and finding ways to make them happen. These examples include making a highly reflective surface using different layers of silicon dioxide and hafnium dioxide which stayed 5°C cooler than the surrounding air (https://www.nature.com/articles/nature13883). Once again, this isn’t a paint but this team has made a lot of efforts in decreasing solar radiation by utilizing different materials and films to be retrofitted on different surfaces, especially in buildings.
In this specific project we are using the “Solar Reflective Coating” developed by Creative Paving Solutions. This coating has been tested by researchers at Arizona State University (ASU), who found that using this paint can decrease temperatures in certain outdoor areas, decrease maintenance costs and energy consumption, and prolong the lifespan of the painted surface. As the research surrounding this paint specifically is still in its initial stages there is not any published material to explore. However, the research is being conducted by Dr. Kamil Kaloush of ASU who has already done a lot of work exploring cooling pavements and reflective materials and has also been looking into materials that will cool surroundings and mitigate the urban heat island effect. Some of his previous work can be found here:
Yang, J., Wang, Z. H., & Kaloush, K. E. (2015). Environmental impacts of reflective materials: Is high albedo a ‘silver bullet’for mitigating urban heat island?. Renewable and Sustainable Energy Reviews, 47, 830-843. https://doi-org.yale.idm.oclc.org/10.1016/j.rser.2015.03.092
Wang, C., Wang, Z. H., Kaloush, K. E., & Shacat, J. (2021). Cool pavements for urban heat island mitigation: A synthetic review. Renewable and Sustainable Energy Reviews, 146, 111171. https://doi-org.yale.idm.oclc.org/10.1016/j.rser.2021.111171
Gui, J., Phelan, P. E., Kaloush, K. E., & Golden, J. S. (2007). Impact of pavement thermophysical properties on surface temperatures. Journal of materials in civil engineering, 19(8), 683-690. https://doi.org/10.1061/(ASCE)0899-1561(2007)19:8(683)
Golden, J. S., & Kaloush, K. E. (2006). Mesoscale and microscale evaluation of surface pavement impacts on the urban heat island effects. The international journal of pavement engineering, 7(1), 37-52. https://doi.org/10.1080/10298430500505325
The Solar Reflective Coating is more commonly used on flat surfaces and pavements (namely rooftops and asphalt surfaces), as is the case with most common uses of this cooling paint. Hence, using it for this mural will be a novel method of use. Once this mural is installed, we can learn about whether these paints can be used for purposes including murals and other vertical wall applications and it will be able to guide future work of a similar scale. We are hoping to get to know the effects and possible limitations of using this paint and will be conducting experiments by taking the temperatures before and after installation to come to our conclusions.
In an era of increasing global climate adversaries, it is important to explore different ways in which climate change communications can be effectively relayed to the public, which is something that scientific research often struggles to do. This Cool Mural is a greatly effective way to reach the eyes of the masses is through public art while advocating for a great and important message.