Estimating ventilation rates in a window-aired room using Kalman filtering and considering uncertain measurements of occupancy and CO2 concentration

This paper describes a method for estimating ventilation rates in a window-aired room considering “in-use” conditions and uncertainty in occupancy (CO2 release) and in measurements of indoor air CO2 concentration. Estimates are drawn from indoor air mass conservation principles and an Extended Kalman Filter, serving as state observer. The modelling procedure is described and tested against synthetic time series generated from pseudorandom values of occupancy and ventilation rate. Additionally, data collected from a case study (a window-aired classroom) is used to illustrate how the procedure is applied and its practical interest. Test results confirm the state observer's tracking capability and confirm its ability to reconstruct ventilation rates in the presence of sudden changes caused by window opening/closing and intermittent occupancy. Results for the case study highlight the benefits derived from knowledge of ventilation rates in window-aired rooms.