Study on ventilation issues in urban nursery facilities: Long-term field survey in Yokohama, Japan

Abstract

In many urban nursery facilities in Japan, daily ventilation behavior is restricted, and poor indoor air quality has been an issue of concern. However, the lack of specific common standards for indoor environments, including ventilation in nursery facilities, has left the issue unresolved in Japan. The purpose of this study is to clarify ventilation issues at nursery facilities in urban areas and indicate future measures. To this end, indoor air quality was analyzed using data from intermittent measurements taken between 2014 and 2022 at 21 nursery facilities in Yokohama City. As a result, the nursery facilities were classified into three categories based on nursery teachers’ ventilation behavior: “window-ventilation type,” “mechanical-ventilation type,” and “combined-ventilation type.” There was a significant difference (p-value <0.001) in the mean CO2 concentration between the window-ventilation type and the mechanical-ventilation type, and between the window-ventilation type and the combined-ventilation type, confirming the difference indoor air quality due to the difference in ventilation behavior. It was clear that the mechanical-ventilation type and combined-ventilation type had significantly lower compliance rates with the minimum ventilation rate required by the Japanese Building Standard Law (20 m3/h), which buildings must have at a minimum.