Performance assessment of passive building envelope considering microclimate and shadows in urban context

The passive building envelope, incorporating radiative cooling or thermochromic technologies, has garnered growing interest for mitigating rising building energy consumption. However, most existing studies focus on individual buildings and overlook real-world urban microclimates and contextual shading, leading to discrepancies between simulated and actual performance. To address this, we developed a simulation framework that evaluates the energy performance of passive envelopes while accounting for the urban heat island (UHI) effect and shading from surrounding buildings. Using Guangzhou as a case study, four inter-building spacing scenarios were modeled based on local geographic and regulatory contexts. Results show that UHI effects raised the average ambient temperature by 1.13–1.36 °C, which in turn reduced the energy-saving potential of passive radiative cooling (PRC) and thermochromic window (TCW) to 90.9–93.0 % and 90.0–92.8 %, respectively. Contextual shading lowered building cooling load by 32.7–46.2 %, further reducing the energy-saving potential to 73.4–85.5 % for PRC and 15.2–41.1 % for TCW. When both urban impacts are considered, the energy-saving potential of buildings with PRC and TCW decreases by 62 %. This study highlights the importance of incorporating urban factors in the design and deployment of passive building envelope technologies to ensure their potential in real-world applications.