Indoor air quality in school buildings: Experimental monitoring and model validation across different climatic zones

This paper presents the results of a comprehensive indoor air quality (IAQ) monitoring campaign in school classrooms equipped with CMV systems across two distinct Italian climate zones: Alpine (Bolzano) and continental temperate (Nereto, Teramo). Continuous monitoring of CO2, temperature, and relative humidity was performed over seven days in November 2025 at 1-minute resolution (10,021 and 10,079 valid records, respectively). Compliance was assessed according to EN 16798, which establishes Category I as the target for sensitive spaces such as schools. Results demonstrate that both sites achieve Category I conditions for 90.1% (Bolzano) and 89.1% (Nereto) of the measurement period, substantially exceeding recommended thresholds. Zero Category IV exceedances occur at either site, indicating that CMV systems maintain adequate reserve capacity despite operating at ~50% of design capacity. A TRNSYS building energy simulation model was developed, calibrated, and validated against measured data (CV-RMSE: 18.6 % Bolzano, 27.9 % Nereto), meeting ASHRAE Guideline 14-2023 acceptance criteria. Climate-dependent humidity management is critical: Bolzano exhibits problematic desiccation (33.6% RH), while Nereto achieves adequate conditions (50.2% RH). The validated model enables energy-IAQ optimization analyses and supports development of evidence-based school ventilation standards for diverse climatic contexts.