| Summary: | Daylight plays a significant role in achieving energy saving and comfort in buildings. It is in accordance with the human circadian rhythms and allows the best visual conditions in work environments and residential buildings. Recently, numerous researchers have focused their attention on the performance of technological devices able to increase natural light availability in interior areas of buildings. Among them, light shelves are commonly used with the aim of improving the depth of daylight penetration, trying to reduce the non-uniform diffusion of light entering from vertical windows. In this paper, the authors propose six different configurations of an internal-external light shelf and analyse their performance using the experimental scale model approach under real sky. Although the method is not very accurate as deduced from literature on this topic, the authors still demonstrate its usefulness in examining different geometric configurations of light shelves. In fact, even if the results highlight inaccuracies in the method used, which are accentuated under direct sun light, they are useful for considerations in the comparative analysis, particularly in regard to data logged under partially completely cloudy skies albeit with the awareness that light shelves’ effectiveness is improved under direct sun light. Despite its limits, the method is simple to use and can be considered efficient in allowing the authors to carry out considerations regarding the performance of the system analysed. Among the six different configurations proposed two seem to be the most efficient and are characterized by the presence of an internal highly reflecting surface applied on the ceiling and an external one with two different inclination angles (10° and 20°).
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