Impact of Different Luminous Efficacy Models on the Calculation of Lighting Energy Uses in Non-residential Buildings

Artificial lighting has a relevant impact on the electricity uses in non-residential buildings. The calculation method introduced in the relevant EN standards takes into account, only to some extent, the daylighting role on the lighting performances of buildings. An alternative method is under development for the Italian territory, which introduces a climate based approach to properly estimate the day light contribution. The method requires the implementation outdoor global and diffuse illuminance Typical Meteorogical Years (TMY), which calculated starting from solar irradiation data and luminous efficacy models. Different models can be used for this purpose, consequently these differences may lead to different estimates of daylight availability in buildings during the year. This paper explores the impact of different luminous efficacy models on the lighting energy uses in non-residential buildings. A typical office building is used for the study and calculations are carried out for three localities of the Italian territory. The outdoor luminous environment, the reference indoor visual task and the building daylight characteristics are taken into account. Results allow to compare the energy lighting performance of the building applying the different luminous efficacy models and, as a consequence, to select the most suitable model to be used in a climate based artificial lighting calculation method.