Exploring the Potential of Egyptian Blue for Enhancing Visual Comfort and Passive Cooling

Enhancing energy efficiency of the building sector is a key element in the decarbonization process outlined by European policies. It is essential to mitigate the construction sector’s environmental impact, especially in relation to the building heritage, which constitutes a significant portion of the Italian building stock. Nevertheless, heritage buildings represent a major challenge, since they are often highly energy-consuming and subject to numerous restrictions, hindering the implementation of traditional energy efficiency measures. Therefore, defining technologies and strategies for optimizing historic buildings’ performance is crucial, particularly in relation to the transparent envelope, which contributes up to 50% of heat loss and to most of the solar heat gains. In this context, passive daytime radiative cooling (PDRC) strategies can effectively mitigate buildings’ surface temperature by regulating indoor conditions as well as decreasing urban ambient temperatures. Among them, photoluminescent films, with their ability to modify their chromatic and emission properties in response to external radiation, seem promising candidates for energy-efficient applications. Recently, Egyptian blue (EB), an inorganic pigment composed of CaCuSi4O10, has gained attention due to its stability, high Near-Infrared reflectance and photoluminescence. This paper provides preliminary analysis of the spectral behaviour of three commercial blue pigments, carried out to evaluate their potential implementation in promising new PDRC solutions. Results demonstrate that the most commercial and widely used option, Cobalt blue, is not the best performing compared to other commercial—yet more sustainable—options, namely a Han Chinese Blue and an EB, confirming the promising PDRC potential of the latter.