Abstract
There are so much of researches underway in order to find out the solution to 22% higher lighting energy consumed by a building. In particular, many studies on light shelves are ongoing due to the merits such as guiding light inflow into deep inside a building as well as allowing excessive shading. The existing literatures fail to provide adequate basis in designing light shelves for various sized space, as they are limited only to performance evaluation on variables of light shelves. In this study, performance evaluation on light shelves was performed by dividing space depth at the interval of 1m for 3-8m, to draw a conclusion as follows: 1)First, the analysis resulted in 6m, 4m and 3m of space depth that entirely meets standard intensity of illumination 400lux, with light shelves not installed for Winter Solstice, Summer Solstice and Spring/Autumnal Equinox Day, while it showed 4-6m, 3-4m and 3-4m with light shelves installed in depth and at angle as specified by this study, telling us there was no Daylighting Efficiency by changes in space depth except Summer Solstice even with light shelves installed. 2)The performance of light shelves depended on, in order, the specular surface of light shelves, the reflection of ceiling and the position of third reflection to be changed by space depth which have to be considered as an element in designing. Especially in the cases of at the angle of $20^{\circ}$ during Winter Solstice and angle of $30^{\circ}$ during Spring/Autumnal Equinox Day, extra care should be paid while designing a light shelf that will directly guide light inflow to indoor through its specular surface. 3)As the depth of light shelf increased, the shade size caused by light shelfrose along with higher uniformity ratio of illuminance, while it reduced with less uniformity ratio of illuminance as the angle of light shelf increased. 4)Considering the space depth set by this study, light inflow and reflection type through light shelf and uniformity ratio of illuminance, the adequate proposals were drawn as an external light shelf of $10^{\circ}$ and 0.3m in depth, an external light shelf of $20^{\circ}$ and 0.3m in depth, and an external light shelf of $30^{\circ}$ and 1.2m in depth, for Winter Solstice, Spring/Autumnal Equinox Day, and Summer Solstice, respectively. However, for Summer Solstice, it was determined that the most appropriate proposal was an external light shelf of 0.3m in depth, considering the fact that an external light shelf with the angle of $30^{\circ}$ is efficient in general and that the angle of a light shelf is changed by operation. This study provides meaningful performance evaluation on light shelf by space depth. Further multilateral studies will be required in consideration of the height and the depth of space as the element of space size.
