Exploring the impact of opening ratio on indoor thermal environment: A study on natural ventilation design

The utilization of natural ventilation to reduce thermal load and enhance thermal comfort in buildings is on the rise. Furthermore, in light of the COVID-19 impact, natural ventilation is gaining prominence as an increasingly vital technology. However, it is crucial to address potential challenges associated with natural ventilation, particularly its impact on the indoor thermal environment. This study aimed to examine and offer insights into natural ventilation design and operational strategies for office buildings. We initially summarized the criteria and effective opening area of natural ventilation openings (αAi) in Japanese naturally ventilated buildings. Among the 37 investigated office buildings, we found a positive correlation between the natural ventilation room area and the αAi. Approximately, 25 buildings maintained a ratio of αAi to the natural ventilation room area ranging from 0.1%–0.5%. Additionally, we conducted measurements of the indoor thermal environment, focusing on the opening ratio of natural ventilation openings. The difference of indoor and outdoor temperature showed a strong negative correlation with the opening ratio, while wind direction and global solar radiation exhibited significant correlations as well. These research findings provide valuable insights for future natural ventilation designs and the incorporation of opening ratio concepts into operational methods.