Visual discomfort and glare rating assessment of integrated daylighting and electric lighting systems using HDR imaging techniques

The integration of daylighting and electric lighting systems within buildings (also designated as ‘green lighting’) is a recent issue for the lighting research community: it allows achieving better lighting conditions for building occupants, in particular within office rooms. Besides the substitution of electric light, daylighting can contribute in a significant way to improve the users' visual comfort and performance, with a large variety of novel daylighting systems and components being developed in recent years. In order to demonstrate this, an anidolic daylighting system combined with several electric lighting fixtures was set up in an office room of the LESO solar experimental building located on the EPFL campus in Lausanne (Switzerland). Three different electric lighting modes, involving recessed luminaries (direct lighting), floor lamps (indirect lighting) and desk lamps (task lighting), were considered for that purpose. Luminance contrasts and glare indexes in the occupants' view field were monitored and compared in the office room, both in the presence and absence of daylight and for different sky conditions; the latter was achieved through luminance mappings based on high dynamic range imaging techniques. The energy performance of electric lighting systems was also considered, together with the qualitative aspect of lighting, in order to outline the main features that characterize an optimal integration of daylighting and electric lighting systems.