Multizone representation of time-varying airflows in naturally ventilated dwellings: Occupant-generated CO2 approach

Accurate measurement of air exchange-rates (AERs) is crucial in naturally ventilated dwellings. AER calculations must take into account the multizone and time-varying aspects to avoid significant deviations from reality. To address the issues of invasiveness, high cost, and inability to track real-time changes in airflow and to represent real airflow patterns associated with the multiple tracer gas methods, this study proposes a practical and feasible approach, belonging to the occupant-generated CO2 methods, for the multizone representation of time-varying airflow in naturally ventilated dwellings. In this approach, the idea of state traversal is introduced to account for all possible airflow patterns. For each airflow pattern, the transient indoor CO2 mass balance equation associated with Kalman filter, and the dynamic simulation of indoor temperature are applied to successively determine the airflow pattern that is closest to the actual pattern. The approach's reliability for multizone representation of airflow is validated in controlled multizone environments, and its applicability to natural ventilation of real residential situations is also evaluated. This study further examines the zoning criterion and the approach's correction capability, while also providing a detailed analysis of its strengths and weaknesses.