Optimal transition temperature maps of thermotropic glazing in a reference office room of China considering the building performance

• Reference office room with 4 orientations of 203 cities in China was studied. • Performance of TT + Low-e H was compared with single TT and low-e double glazing. • The optimal transition temperature and potential improvements maps were plotted. • The optimal transition temperatures were compared by Köppen climate classification. Thermotropic (TT) glazing is gaining increasing interest due to their unique ability to regulate solar heat gain and visible daylight transmittance in response to temperature changes. Determining the optimal transition temperature and evaluating the potential improvements of thermotropic glazing in building performance are critical for its application in buildings. In this study, an experimentally validated building performance simulation model for thermotropic glazing was utilized to assess the performance of a reference office room across four building orientations, using typical meteorological year data from 203 cities in China. The optimal transition temperatures were determined, and the potential enhancements in building performance were evaluated through comparisons of single thermotropic glazing, low-e double glazing, and a combination of single thermotropic glazing with a low-e coating featuring high solar heat transmittance (TT + Low-e H). Additionally, spatial distribution maps illustrating the optimal transition temperatures of thermotropic glazing, as well as the potential for energy savings, daylighting, and thermal comfort improvements, were plotted. The results indicated that: (1) TT + Low-e H achieved energy savings of up to 9.5 % in Northern regions and 5.2 % in Southern regions, with the most significant savings observed on West-facing walls. (2) Additionally, TT + Low-e H improved daylighting comfort (sUDI 300∼3000lx, ≥50% ) by as much as 33 % in Northern regions and 32 % in Southern regions, while simultaneously reducing the excessive daylighting range (sUDI >3000lx, ≥50% ) by up to 66 %. (3) Furthermore, thermal comfort levels increased by up to 18.0 % in Northern regions and 13.7 % in Southern regions, with enhancements noted in 60.7 % and 61.4 % of cases. The findings from this study are expected to provide valuable guidance for the application of thermotropic glazing.