The role of weather data files in Climate-based Daylight Modeling

• IWEC, Meteonorm and Satel-Light weather files determine similar outcomes.
• TRY weather data always produces considerably lower values.
• Results’ differences appear more significant for Annual and Monthly Light Exposures.
• Results’ differences decrease when analyzing dynamic daylight metrics.
• IWEC, Meteonorm and Satel-Light have very similar global horizontal irradiance values.

This paper illustrates the results of daylight simulations of a simple standalone office carried out using different weather data files (IWEC, Meteonorm, Satel-Light and TRY), for five European locations (Copenhagen, London, Milan, Nancy, Rome).The aim was to analyze the impact of choosing one weather file or another on the prediction of daylight availability in an indoor environment. Results were analyzed both in terms of Annual and Monthly Light Exposures and dynamic daylight performance metrics.It was demonstrated that IWEC, Meteonorm and Satel-Light weather files determine similar outcomes, instead TRY weather data always produces considerably lower values. Moreover the differences between the results obtained with the different weather files appear more significant considering Annual and Monthly Light Exposures, whereas they decrease when analyzing illuminances with a statistical approach (DA, DAcon, UDI).