The Impact of Exterior Surround Detail on Daylighting Simulation Results

ABSTRACT The accuracy of daylighting simulations for the built environment strongly depends on the modeling of the exterior surround. The practice of modeling a space with a flat ground surface with little or no external architectural or landscape elements, particularly early in the design phase, is often applied. In this study, this approach and a number of different levels of detail for modeling the exterior surround were investigated by comparing real-life empirical measurements with their corresponding simulation results. A total of 13 different exterior views were studied under 15 different sky/seasonal conditions to investigate the contribution of the surrounding features to the daylight delivered inside a small office. These features were classified into one of four different groups – sky, architectural structures, standing vegetation, and horizontal ground. Five of these locations were chosen for further simulation by applying six levels of detail to the exterior surround in a simulation model. The results reveal that ignoring exterior surround objects (common practice for some) yielded an average error of 67.9%, while a high level of detail (which applied high polygon vegetation representations) resulted in an average error of only 11.3%. A detailed model of the surround with the IES LM-83 suggested method of modeling trees resulted in an average error of 22.8%.