Paper Conference

Proceedings of BSA Conference 2015: Second Conference of IBPSA-Italy


A new climate-based daylight metric for hot climates

Islam Ayman Mashaly, Yussra Mohamed Rashed, Muhammad Adel, Khaled Nassar

Abstract: Daylight performance metrics are moving away from the traditional daylight factor and average illuminance to more climatic-based metrics such as Daylight Autonomy (DA) and Useful Daylight Index (UDI). These metrics offer a better measure of the daylight performance throughout the year and incorporate the varying weather conditions and as such are dubbed climaticbased metrics. However, in hot climates where the ratio of direct to diffuse is highest, achieving these metrics may result in over-heating the spaces. Achieving acceptable climatic-based metrics for the space may result in unacceptable heat gains. The Daylight Autonomy and the Useful Daylight Index do not account for the total amount of lux-hours achieved throughout the year. The solution thus far has been to run coupledenergy and daylight simulations in order to assess the effect of achieving certain climatic-based metrics on the heat gain and thermal performance of the space. In this paper a new metric is proposed that takes into account the total amount of lux-hours achieved throughout the year and the irradiation for different time steps into a single measure. Details about the measure and sample test cases are presented.
Pages: 155 - 162