Control logics of natural ventilation for indoor air quality: an experimental approach

The control of natural ventilation in winter, generally limited to achieving adequate levels of Indoor Air Quality (AIQ), is of particular interest for the pursuit of energy efficiency targets in working environments and/or for those with high degree of crowding. The building automation systems and the control logics of natural ventilation present on market are usually based on presence sensors and indoor air pollution, but they do not modulate adequately the air flow in function of the pollutant production rate and of the other boundary conditions. Therefore this work focuses on the building's response to the different window opening configurations and for different climatic conditions. For this purpose, a calculation procedure of air flow for natural ventilation is defined, based on the monitoring of the indoor carbon dioxide (CO2) produced by the occupants and assumed as tracer gas. The calculated flow rate is used for defining the building's response in function of wind characteristics and of the thermal gradient between the indoor and the outdoor. In the second phase, an algorithm is defined to control window opening in order to 1) predict the evolution of the indoor pollution rate, 2) prevent the possible overcome of CO2 acceptability thresholds and 3) manage the window opening degree to guarantee the strictly necessary flow rate. This work presents the first results of the experimentation conducted at Polytechnic University of Bari.