Evaluation and Analysis of the Efficiency of Dynamic Metrics Evaluating Daylight Performance (Daylight Autonomy and Useful Daylight Illuminance) through Sensitivity Analysis; Case Study: Elementary Classroom in Tehran

To achieve sustainable, low-energy buildings, it is required to further emphasize on accurate evaluation of daylight performance. To this end, over the last few years, researchers have considerably developed more advanced dynamic metrics to overcome the limitations of static metrics. Nowadays, Daylight Autonomy (DA) and Useful Daylight Illuminance (UDI) metrics and those metrics developed based on these two are the most well-known dynamic daylight performance metrics, which do not have the same credit in terms of efficiency among different experts. The present study aims to compare the abilities of these metrics to be used in evaluating daylight performance in educational buildings. To this end, a parametric analysis is performed through simulation in Grasshopper software using Ladybug and Honeybee plugins. This analysis is performed to show the relationship between UDI, sUDI, DA, sDA, cDA metrics by examining the effects of the variations of Window-to-Wall Ratio (WWR) on them in a typical Classroom of an elementary school in Tehran. The results show that the lack of a high limit for DA and DA-based metrics, i.e. sDA and cDA, eliminates their correlations with the components related to the occupant comfort. Among various daylight metrics, UDI, due to its correlation with glare and energy consumption, can indicate the propensity for the occurrence of occupant discomfort as well as the energy consumption. Also, among UDI-based metrics, sUDI needs to increase the density of sensor points in the grid to achieve the same accuracy as UDIavg, significantly increasing the computation time. Therefore, the UDIavg metric is more suitable to use for small spatial units where the number of sensors is quite limited.