Life cycle assessment of thermotropic glazing for a reference office room across three warm-climate cities in China

Smart window technologies can reduce building energy use, but their additional materials and manufacturing processes may increase embodied carbon. Thermotropic (TT) glazing is promising for reducing cooling demand in warm climates. Although previous studies have mainly focused on the energy performance of TT glazing, it remains unclear whether its operational carbon savings can offset the additional embodied carbon over the full life cycle. To address this gap, this study combines primary industrial inventory data with EnergyPlus simulations to evaluate the full life-cycle environmental performance of TT glazing. TT glazing was compared with conventional double glazing (DG) for a reference office room in Xiamen, Nanjing, and Chongqing, China, across the product, construction, use, and end-of-life (EOL) stages. Primary production data were obtained from a field investigation at Chongqing Hewei Technology Co., Ltd., and EnergyPlus-simulated energy use was used to calculate operational carbon emissions. The production-stage carbon emissions of TT glazing were 62.93 kg CO₂e/m². Compared with DG, TT glazing had higher embodied carbon but reduced operational carbon emissions by 14.0%, 7.6%, and 2.0% in Xiamen, Nanjing, and Chongqing, respectively. Based on curing-process and simplified grid decarbonization scenarios, the carbon payback period (CPP) ranged from 0.4 to 6.2 years, remaining below the assumed 30-year service life. ReCiPe 2016 results further indicated lower environmental impacts for TT glazing under the studied scenarios. These findings suggest that TT glazing has the potential to reduce life-cycle environmental impacts under the modeled single-room, south-facing façade, and landfill-only assumptions.