Membrane Structures as a Shelter Solution for Privately Owned Public Spaces: Evaluating Heat-Related Risk During Disasters and Daily Thermal Comfort via Simulation

This study evaluated whether membrane structures can enhance thermal comfort and reduce heat- and cold-related health risks in privately owned public spaces (POPS) under representative seasonal peak conditions. Based on previous in situ measurements revealing severe summer heat stress and winter cold discomfort in two POPS in Tokyo’s Minato-ku Shibaura district, a membrane-based shelter solution is proposed and systematically assessed. Their thermal environmental effects were numerically simulated using a coupled surface energy balance (SEB) and computational fluid dynamics (CFD) model, with evaluations focusing on human health risks and thermal comfort. Results demonstrated that in summer, membrane structures effectively improved thermal comfort by reducing the standard effective temperature (SET*) by 1.9–3.9 °C, although these SET* values still remained above the thermal comfort range. Notably, heat stress-related health risks were significantly mitigated, as deep body temperature (DBT) decreased by 1.2–1.6 °C, falling below the 38 °C heatstroke risk threshold. In winter, although the overall improvement was limited, the membrane structures still reduced cold-related health risks and extended allowable exposure duration (AED). Furthermore, auxiliary measures (e.g., mist sprays for summer and supplementary heating for winter) are recommended to further enhance thermal comfort in POPS.