Suitable transition temperature on thermo-adaptive reflectance for opaque facades: Influence of climate, solar orientation, and facade material

Abstract

Thermo-adaptive reflectance (TAR) opaque facades change their solar reflectance in response to temperature variations. This behaviour can be optimised to improve indoor thermal comfort by tailoring the transition temperature (TT), i.e., the temperature in which the solar reflectance changes. The study aims to identify which factors influence the suitable transition temperature (STT), i.e., the transition temperature that enables achieving the lowest total degree hour, and the magnitude of the benefits of applying TAR concept to opaque facades. A 3D model was created to assess indoor thermal comfort by running dynamic thermal simulations. Resorting to the energy management system, the solar reflectance variation based on the external face’s temperature was possible, enabling thermo-adaptive reflectance emulation. A parametric study was conducted, considering three solar orientations, four density facade categories and four different climates. For each scenario, the STT for TAR on opaque facades was determined by considering the lowest total degree hour. Two multiple regression models were generated using the sample comprising the case studies in which the most STT was used. The entities (case studies) were characterized by variables covering the climate, facade solar orientation, material, and comfort subjects. The analysis identified climate as the primary influencing factor on the STT, followed by facade material and solar orientation. The impact of TAR on the relative total degree hours improvement was significantly influenced by the facade material, followed by climate. Concluding that TT prescription is mandatory for each facade, even within the same building, and that TAR concept application is not universal.