Simulation of modern passive stack ventilation in a retrofitted Nordic apartment building

Some heritage or protected residential buildings in Nordic conditions require retrofit; however, having limited or no access to the reconstruction of the ventilation system; thus, the native natural ventilation system must be preserved. Some retrofitted buildings are then equipped with modern passive stack ventilation systems implemented with self-regulated supply inlets. Although natural ventilation strongly depends on climate conditions, creating challenges in the design phase as the indoor air quality can not be guaranteed. In this study, such a building was modelled, and a novel self-regulated inlet component was created and applied to the simulation model of the multi-storey residential building with natural ventilation in the Nordic conditions. This IDA ICE model is implemented with a self-regulated inlet model with outdoor temperature control and simulates the yearly performance of a ventilation system, considering the effect of outdoor conditions, such as air temperature and wind direction. The self-regulated device is represented as a one-direction opening based on power-law with variable internal airflow resistance, calculated based on the outdoor simulation temperature. Several case scenarios of the multi-storey residential building with passive stack and windows opening ventilation were created for the analysis. The cases present possible maintenance issues, such as inlet device dirty filter and passive stack ducts, structural differences, such as envelope airtightness level and occupant behaviour, such as internal apartment doors and windows operation. The resulting CO2 concentration, indoor air temperature and air change rate were analysed and compared against indoor air standards. Overall, the building model simulation results coincide well with studies in comparable conditions; the novel self-regulated inlet device was simulated according to the manufacturer data. The resulting simulation model could be used to assess the performance of modern passive stack ventilation under different climatic conditions.