Applications of thermochromic material in opaque building envelopes: A comprehensive review

Solar radiation heat gain can lower the air-conditioning energy consumption and improve the thermal environment in winter while it is in summer. However, the traditional building skin material does not address the difference in thermal demand between winter and summer due to the constant solar reflectance. An innovative solution to this issue is the use of thermochromic materials (TCMs), which are capable of altering their colour and solar reflectance in response to temperature changes, thus aligning with the seasonal thermal requirements. Despite the potential of TCMs, a thorough analysis of their advantages and drawbacks to inform their practical application has been lacking in the literature. This review provides an overview of the classification and discolouration mechanism of TCM, performance measurement indicators and evaluation methods, and the main factors affecting the application efficiency of TCM. It provides a comprehensive account of the application efficiency of TCM in the thermal environment of urban buildings and building energy consumption. Finally, the review concludes with suggestions for future research avenues and potential applications, taking into account the limitations currently impeding the full realization of TCMs' efficiency.