Jaue2025-023 Toward Improved Cooling: Field Investigation of Summer Thermal Environment in Classrooms of Hot Summer and Cold Winter Regions

Abstract

Teaching buildings in the Hot Summer and Cold Winter (HSCW) Regions commonly experience high temperature, high humidity, and insufficient ventilation efficiency during summer, particularly under conditions without active cooling. However, targeted investigations into the spatial distribution characteristics of indoor thermal environments and the auxiliary role of fans under such conditions remain limited. To explore the effectiveness of fan assistance in improving thermal uniformity under natural ventilation, this study selected university classrooms in Chengdu as the case study. Field measurements were conducted in two unoccupied classrooms during a representative teaching period in September, and indoor thermal parameters were continuously monitored under two conditions: natural ventilation (NV) and natural ventilation with fan assistance (NV + Fan). Particular attention was given to the vertical distribution characteristics at four heights: 0.1 m, 0.6 m, 1.1 m, and 2.6 m. The results indicate that, in the absence of active cooling, indoor air temperature fluctuations were significantly smaller than those outdoors, suggesting that the thermal inertia of the building envelope can mitigate the impact of short-term outdoor heat disturbances to a certain extent. Compared with the NV condition, the average indoor air temperature under the “NV + Fan” condition increased slightly, while vertical thermal stratification was substantially weakened, with the maximum temperature difference between the upper and lower layers reduced by approximately 30%. Meanwhile, the vertical relative humidity difference decreased from approximately 10% to 1%–5%, demonstrating that fan operation effectively enhanced indoor air mixing and improved the uniformity of temperature and humidity distribution within the classroom. The findings suggest that, although fans may not directly reduce indoor air temperature in university buildings located in the HSCW Regions, they can serve as an important auxiliary measure for natural ventilation by significantly optimizing the spatial thermal environment distribution of teaching spaces. This study provides practical implications for low-energy summer operation strategies in educational buildings.