Thermochromic and cool coatings for buildings

What is it about?

Cool coatings show high solar reflectance and have been proposed to decrease the building energy demand by reducing solar heat gains. However, cool coatings may have a negative effect during cold seasons when solar gains would be beneficial. Thermochromic coatings, thanks to their ability to change their solar reflectance at different temperatures, have been proposed to reduce the heating penalties during colder seasons of traditional cool coatings. In this work, four different thermochromic pigments have been used to create façade paints. The solar reflectance and thermal emissivity of these paints have been evaluated experimentally. A significant change of 0.37 in the reflectance of the four paints was registered in the visible range. These products are hence compared with common cool coatings available on the market. In order to evaluate the potential energy savings of thermochromic paints, an office building in downtown Toronto (Ontario, Canada) and the surrounding area have been modeled in Energy Plus. Different scenarios have been simulated and compared among conventional, cool, and thermochromic coatings applied on the roof or on the building facades. The study also evaluates the different new coatings under several climate change scenarios. Overall results show that for the context of analysis, thermochromic paints can provide an 8.9% decrease in the cooling demand, while limiting the winter penalties to 1.7%, compared to the heating penalties of 2.6% resulted using A cool coating. Despite the limited heating penalties, the annual energy demand for all the simulated scenarios is comparable. Similar results were also obtained when the inter-building effects were taken into account in the analyzed context. Finally, thermochromic paints proved to be more beneficial considering future climate conditions as Canada is projected to show significantly higher cooling energy demands.

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Photo by Anders Jildén on Unsplash

Photo by Anders Jildén on Unsplash