A methodology to integrate advanced lighting and thermal analyses for building energy simulation

It is well known that an appropriate daylighting design can influence the global energy performance of a building as well as the visual and thermal comfort for the occupants. Furthermore the increasing awareness of the potential benefits of daylight has resulted in an increased need for objective information and data on the impact that different design solutions can have on the daylighting condition within a space, in relation with the architectural features. This kind of analysis is becoming more and more requested, during all stages of the design process. The purpose of this paper is to describe a reliable simulation approach to consider daylight when assessing the energy performance of a building. The methodology is based on the use of both Daysim and EnergyPlus which were employed in synergy for a parametric study to assess lighting and energy performances of rooms with different architectural features: orientation, window size and glazing visible transmittance, room depth, external obstruction angle and site. Daysim was chosen to perform daylighting analyses since it allows us to accurately estimate the annual amount of daylight in a space and calculating climate-based daylight metrics as well as the annual electric lighting use for different lighting controls. The Daysim output file that describes the status of all lighting and shading groups in the space during the year was then used as input in EnergyPlus to estimate the influence of the daylighting and artificial lighting design on the global energy performance of a space. The paper presents some considerations on the simulation approach adopted in the study and the most important results that were obtained in terms of daylighting conditions and energy demand for lighting, heating and cooling, to demonstrate the substantial influence of daylight harvesting on the reduction of the global energy performance.