Passive Design Involving Multi-Performance Optimization and Cascading Optimization of Active Airflow Mode for the Sentry Box Buildings

Sentry box buildings present excessive energy consumption and poor thermal comfort due to the lightweight envelope. Therefore, a framework integrating passive design with multi-objective optimization and cascading active airflow mode optimization for sentry box buildings was developed in the study. First, a parametric model for the prototype of sentry box buildings in the cold zone of China was developed. The global sensitivity analysis based on the treed Gaussian process was employed to select key design variables. Furthermore, backpropagation neural network prediction models for the UDI, PPD, and EUI of sentry box buildings were developed based on the dataset, which was generated via Latin hypercube sampling and building performance simulation in Grasshopper. Subsequently, the NSGA-II algorithm was selected for multi-objective optimization, combined with entropy-weighted TOPSIS analysis, to determine the optimal values of the design variables for sentry box buildings. Finally, the optimal airflow mode and velocity of sentry box buildings for summer and winter were selected through cascaded CFD simulations. The results indicate that the window-to-wall ratio is the most influential design variable across the optimization objectives of sentry box buildings. The prediction models achieve high accuracy, with the lowest coefficient of determination R of 0.994 and the highest mean squared error of 0.001. The optimized design improved performance across all objectives compared to the prototype of sentry box buildings, with UDI increasing by 77.433%, and PPD and EUI decreasing by 18.282% and 28.668%, respectively. Interestingly, the sentry box buildings should adopt a horizontal attached airflow mode at 1.5 m/s in summer and a vertical attached airflow mode at 1.8 m/s in winter. In summary, a decision-support tool was introduced in the study for the early design stage to assist in selecting optimal design solutions for the sentry box buildings.