Abstract
Ventilation of office buildings affects the indoor air quality IAQ perceived by the occupants, their wellbeing, as well as their task performance. Although many offices are equipped with mechanical systems, new complex and hybrid solutions have been under consideration since the pandemic, combining for instance mechanical and natural ventilation with portable air-purifiers to ensure high IAQ and energy performance. In this context, this research proposes a framework aimed at defining an optimized hybrid ventilation strategy by prioritizing, when convenient, the utilization of outdoor airflow, combined with mechanical ventilation and an optimized use of air-purifiers. As a proof of concept, the presented framework is applied through a calibrated multi-zone building energy model representative of public office buildings designed and constructed in the 1990s in Bolzano, Italy. Mass flow rates among the zones of the building, calculated by the simulation model, are used to estimate the pollutant concentrations. The fresh air change rate, required to maintain the pollutant concentrations below the law thresholds, is determined thanks to a mass balance model, prioritizing natural ventilation by opening windows. In the case of unavailability or inefficacy of natural ventilation, to keep adequate IAQ, priority is given to the least energy consuming option between the use of air-purifiers and the mechanical system. Finally, the application of the proposed framework as an advanced control logic, such as a model predictive control strategy, is discussed, considering also its potential implementation to other office buildings.