Impact of behavioural patterns on the energy use of a residential nearly-zero energy building

Occupant behaviour (OB) is one of the most significant sources of uncertainty in the prediction of building energy use by simulation programs. Extended literature reviews confirm that the accurate evaluation of occupant behaviour is a key factor for bridging the gap between predicted and actual energy performance of buildings. Indeed, occupant behaviour affects the real building energy use directly and indirectly by regulating the heating and cooling set point, the ventilation rate, the window blind position, turning on/off or dimming lights, turning on/off equipment, and setting indoor thermal, acoustic and visual comfort criteria. Previous field studies measured the impact of occupant-driven parameters on energy consumptions in residential buildings means to data gathering set ups and monitoring campaigns. The outcomes showed large discrepancies in the effect of occupant behaviour among houses in a community and across communities, with corresponding large impacts on energy use. In detail, some studies have shown that the behaviour of the household members may lead to differences in energy consumptions of over 300%. In second place, in the past twenty years, more stringent energy codes and environmental standards have led to many high performance building designs that use less energy. In these kinds of buildings, once optimized the envelope and building systems, the unpredictable loads generated by the occupants gain greater influence than in a house whose envelope-driven loads dominate the consumption profile. Indeed, the success of high energy performing design strategies is now heavily dependent on how occupants interact with the building. This study employs and compares building simulations carried out in (i) IDA ICE (4.6.2)and (ii) Energyplus (version 8.4) to demonstrate the potential impact of occupant behaviour lifestyles on energy use in a residential nZEB under-construction, the so-called CorTau House in North Italy. In detail, occupant behaviour was classified into three lifestyles: low consumer, standard consumer and high consumer. The analysis considered energy-related behavioural patterns (regulation of heating and cooling set points; energy use for equipment, lighting and DHW; ventilation rates; regulation of window blinds) and highlighted key variables, which need to be addressed by decision-makers of behavioural change programs for conscious use of nZEBs. The results obtained in this study reveal that the energy-related occupant behaviour lifestyles significantly influence the energy performance of the analysed residential nearly-zero energy building. Thus, a building can only be considered a nearly-zero energy building if zero-capital actions related to the behavioural change of the occupants become as important as technological high performing solutions for the building features. Indeed, if the behaviour of the inhabitants is energy wasting, it might be unmanageable to reach the nearly-zero energy target, even if the building itself is defined “high performing”; the occupants need to be proactive in saving energy as well. The most influencing occupant driven variables on final energy consumptions are related to the equipment use in first place and secondly to the lighting use. Indeed, the unpredictable loads related to these variables gain greater influence than in buildings whose envelope-driven loads dominate the consumptions profile. Finally, the comparison of the abovementioned simulation softwares showed that the overall results for the different final energy uses were slightly higher in IDA ICE than in Energyplus (Figure 1). It is worth noting that the final energy use for domestic hot water was calculated separately in the Energy Plus model and this led to significantly lower values related to the “Heating+DHW” energy use with respect to the IDA ICE model.