• Energy Research

Abstract The implementation of occupancy-controlled and daylighting-dimmed lighting systems has an impact on the energy consumption of residential buildings. The BAC factor method of EN ISO 52120-1 estimates that 8% of the lighting energy can be saved compared to conventional manual control. However, it is assumed that their ability to potentially lower the lighting energy consumption is strongly related to external factors, such as the extent of daylight entrance and the behaviour of the inhabitants. By means of simulations in EnergyPlus, the performances of automated and manual lighting control are compared for an apartment and semi-detached building located in Brussels (Belgium) with variation in the occupant behaviour and orientation. It appears that an automated lighting control including 0-100% dimmer reduces the lighting energy demand for all investigated cases with savings up to 38.4%, whereas a similar control without dimmer does not necessarily reduce the lighting electricity demand. However, the results show a considerable variation, making prediction methods as the BAC factor method highly inaccurate. The actual relative energy performance depends on the automation system, type of building, orientation and occupant behaviour (i.e. number of inhabitants and occupancy rate). Hereby, the number of inhabitants has the most considerable impact on the relative energy performances with differences up to 50%, while the occupancy rate shows a significant correlation, especially for low numbers of inhabitants.

Abstract: Well-designed and properly implemented Building Automation and Control Systems (BACS) can contribute to a reduction of the energy consumption in buildings, while increasing comfort and convenience for the occupants. For design and planning purposes, there is a need to quantify the potential impacts of implementing BACS, especially related to their capability for reducing the operational energy demand of a building. The simplified BAC factor method defined in standard EN 15232 aims to provide a generic estimation of expected energy savings. Alternatively, dynamic energy performance simulations can provide more detailed insights on a particular building design. Comparing energy savings from BACS in different sources in literature reveals significant discrepancies between various studies and assessment methods. This paper aims to clarify and discuss the differences between the various assessments and to identify the parameters that could affect BACS (i.e. heating, domestic hot water supply, lighting and shading control systems) performance in residential buildings. It is concluded that simplified methods as the EN 15232 BAC factor method do not provide a reliable estimate of achievable energy savings. The results obtained by more detailed simulations reported in literature show a significant variation in BACS performance. Two main causes are identified. Factors such as building and installation design parameters, occupant behaviour, context (e.g. climate) and baseline energy demand affect the energy saving potential but are not explicitly taken into account in the BAC factor method. Next, a significant part of the variation in reported energy saving potential can be attributed to discrepancies in modelling methods.