Case study for deriving appropriate light shelf specifications based on indoor space depth

The light shelf, a natural lighting system, is widely studied for its efficiency. However, previous studies have focused on light shelf variables, with only a few considering room size during installation. This study aims to establish basic data for light shelf design through performance evaluation based on indoor space depth and light shelf variables. Radiance, a well-known ray-tracing software package, was used to derive illuminance distribution and indoor lighting uniformity ratio. Optimal efficiency was achieved with light shelves in indoor spaces deeper than 5, 7, or 6 m during the summer, winter, and middle seasons, respectively. Increasing the light shelf width and angle increased the incident light amount and improved lighting performance in the summer and middle seasons, but a light shelf was unsuitable for enhancing lighting performance and indoor lighting uniformity ratio in winter. Notably, during winter, and middle seasons, the light shelf angle was found to degrade lighting uniformity due to direct natural light entry and non-reflection of ceiling surface. In addition, because appropriate light shelf dimensions are season-specific, movable light shelves with controllable angles were effective. However, for winter, removable light shelves were more appropriate to avoid blocking the sun's rays and increasing heating energy. Overall, this study provides basic data for light shelf design considering various space depths and light shelf variables, but future research is needed to address the limitations of specific performance evaluations.