Comparison of daylight simulation methods for reflected sunlight from curtain walls

Curtain walls are more and more commonly used as building facades. They allow a better daylight availability and a direct connection to exterior environments. Meanwhile, due to the high specular reflections, they may also introduce negative impacts, such as glare and urban heat island effects, to the surround, especially in dense and urban environments. Therefore, it is important to effectively characterize the reflected sunlight from curtain walls. This study aimed to compare how different simulation methods can be used to characterize the reflected sunlight from curtain walls. It was found that the modeling of the sun and sky, ambient calculation, and the modeling of the building facade significantly affected the simulation results. A combination of forward and backward ray-tracing is recommended, with forward ray-tracing for identifying the curtain wall areas reflecting sunlight and backward ray-tracing for calculating illuminance due to reflected sunlight. A follow-up work is planned to investigate how different parameters will affect the simulation results and which method can produce similar results as field measurements.