Evaluation of the impact of window use on the heating energy use and IEQ in dwellings based on simulations

Window opening behaviour can have an important impact on residential energy use, especially in energy efficient dwellings. A few studies indicated that the window use may be a habitual behaviour, meaning that the behaviour is performed without conscious thought as a consequence of frequently repeating this action. Verbruggen et al. (2021a) developed an event-based residential occupant behaviour model (EROB) based on habits as present in Belgian dwellings, including a window opening model. This habit-based approach has some advantages such as the prediction of inter-occupant diversity, easy implementation in Building Energy Simulation (BES) and the prediction of realistic actions that fit in the occupants' day-to-day life. 
However, for application purposes it can be questioned if the inclusion of these habits makes a significant impact on the energy use and indoor climate. Therefore, this paper explores the impact of the habit-based occupant behaviour model on the energy use and indoor climate predictions in dwellings. 
First, the modelling approach is introduced. One of the nearly zero energy houses (NZEB) in a case study neighbourhood has been modelled in the simulation environment Dymola-Ideas. In addition to the actual situation with NZEB performance, the house has also been modelled with a design reflecting a medium and poor energy performance. The library components and modelling assumptions are explained.  
The simulations are carried out for 30 different household profiles, generated using the EROB-model. The evaluation of the impact of user behaviour is based on three criteria: the net energy use for space heating, the CO2-concentration as a measure for IAQ, and overheating as a measure for thermal discomfort. The simulations are carried out for both the overall model and for a base-model including only one type of occupant behaviour, to evaluate which has the largest influence. Additionally, the importance of predicting realistic window use actions, one of the intrinsic characteristics of the habit-based approach, is assessed. 
The simulation results show a significant impact on the energy use and indoor climate predictions due to the inclusion of occupant behaviour, especially by the window use and especially in energy efficient buildings.