Improvement of light-shelf performance through the use of a diffusion sheet

Several studies have addressed the issue of increases in the energy consumption associated with lighting in buildings. The light-shelf is a natural lighting system that efficiently reduces the amount of energy consumed for lighting by drawing natural light into a room through reflection. However, the performance of the light-shelf is reduced as a result of external environmental factors, such as the solar azimuth, and it can also produce glare while drawing natural light into the room. The present study examined the use of a light-shelf with a diffusion sheet, with the goal of improving LED lighting efficiency and reducing glare, and set out to validate its efficacy by evaluating its performance according to the position at which the diffusion sheet was attached. As part of the present study, performance evaluation cases were configured according to the diffusion sheet application and attachment position, and evaluations were conducted using a full-size test-bed. It was found that a conventional light-shelf brought more light into a room than that with the diffusion sheet, but glare was generated at certain angles in each season. However, the proposed light-shelf with the diffusion sheet attached to the upper window glass was analyzed and found to be effective at reducing lighting energy consumption by 2% while improving the glare and uniformity compared to that of a conventional light-shelf. This study is meaningful since it establishes the basic data for future light shelf design by deriving relevant variables and considering lighting energy reduction and glare.