Impact of unoccupied flats on the thermal discomfort and energy demand: Case of a multi-residential building

Abstract

Energy consumption and indoor thermal comfort are two major issues that always come into play in any building retrofit. Furthermore, if the impact of user behaviour and their social activities in buildings must be taken into consideration when defining renovation strategies, the importance of occupancy can also be very important for the performance of the building. This subject is of special relevance in the context of social housing, where the number of unoccupied flats is sometimes quite expressive due to their temporary and intermittent use. A multi-residential social housing neighbourhood was used as a case study to assess the impact of occupancy of different flats on the overall energy savings and indoor thermal comfort of the building. The indoor environment (air temperature and relative humidity), the envelope airtightness (blower door test) of occupied and unoccupied flats and the tenants’ habits were assessed during 7 weeks. The exterior weather data was collected from a local weather station. This data was used to calibrate a numerical model created with EnergyPlus software. The model was used for a sensitivity analysis where the importance of occupancy was evaluated. The occupied and unoccupied flats position (under, over and adjacent) within the building was changed, to assess the impact on the indoor thermal comfort of the occupied flats (according to EN 15251). The results confirmed the importance of occupancy as a decrease of the thermal discomfort rate up to 34.3% for the winter period and an increase up to 85.3% in the summer period were found.