The importance of software's and weather file's choice in dynamic daylight simulations

The prediction of daylight availability in indoor environments is nowadays an extremely relevant topic in the design practice for many reasons: it affects the design of the electric lighting system and therefore the calculation of the related energy consumption; it also has an impact on evaluation of comfort. Dynamic daylight simulations are a helpful tool to predict daylight availability in indoor environments and consequently to evaluate the possible reduction in energy consumptions. However, there are different software packages that perform dynamic daylight simulations and they use different engines and calculation methods which may be a source of differences in the results. Moreover this type of analysis requires a weather data file of the building's location to be performed. Since there are many of them available, which are developed from historical sets of weather measurements using different methods, the use of one or another can affect the simulations' results. Therefore in this paper an example of the impact on dynamic daylight simulations' results of different weather data files (IWEC, Meteonorm, TRY and Satel- Light) and different software (Daysim and 3ds Max Design®) will be reported.