Assessing ventilation performance in schools using continuous CO2 monitoring: Insights from renovation projects

• Build-up and decay periods identification can be automated • Air change rates are significantly higher post-renovation • Daily maximum concentrations of CO 2 are significantly lower post-renovation • Continuous CO 2 measurements provide valuable information about indoor ventilation Well-functioning ventilation is critical for healthy indoor environments. In this study, carbon dioxide (CO 2 ) was continuously measured to assess ventilation performance before and after a major renovation campaign involving 48 school buildings. A novel method was developed to identify build-up and decay periods from the data. Two metrics were then investigated: air change rates (ACRs), which were calculated using build-up and decay periods, and daily maximum concentrations (DMCs) of CO 2 measured during school days. Multiple paired samples t-tests revealed statistically significant changes following the renovations: an increase of ACRs and a decrease of DMCs. This study highlights the feasibility, benefits, and scalability of continuously measuring CO 2 to investigate ventilation performance in schools.