Abstract

Indoor air quality (IAQ) modeling is essential for evaluating and optimizing modern buildings' ventilation systems, pollutant dispersion, and occupant health. Accurate IAQ predictions rely on calibrated models that effectively represent real-world conditions. This study focuses on calibrating the CONTAM multi-zone airflow model using two advanced methodologies: the Ensemble Kalman Filter (ENKF) and the Genetic Algorithm (GA). To improve the model's predictive accuracy, calibration efforts targeted key parameters, including initial CO₂ concentrations, generation rates, and occupancy counts. These methods were validated using CO₂ tracer gas experiments conducted across multiple test scenarios, including room-to-floor and floor-to-floor dispersion dynamics. Results demonstrate that ENKF calibration achieved RMSE reductions of approximately 25% in complex multi-zone airflow scenarios, with CVRMSE consistently below the ASHRAE-recommended threshold of 15%. The GA method performed similarly in accuracy but required higher computational resources, making it more suitable for static or offline calibration processes. The calibrated models were subsequently applied in a case study to analyze CO₂ quanta dispersion in an experimental building with controlled ventilation strategies. This study investigated the effects of varying fresh air percentages (10% to 100%) and stairwell pressurization on contaminant transport. Results from the calibrated models revealed critical insights, such as the effectiveness of high fresh air intake in mitigating pollutant concentrations and the impact of pressurization strategies on inter-zone airflow. These findings highlight the practical value of calibration in refining IAQ predictions and informing operational strategies. This research underscores the importance of hybrid calibration techniques for improving the reliability of multi-zone IAQ models and their application in dynamic building environments. By integrating calibrated models into operational planning, stakeholders can optimize ventilation performance, reduce energy consumption, and enhance occupant safety in diverse building types.