A study on daylighting performance evaluation of light shelf based on the spatial form of inclined ceiling

Abstract

As the lighting energy usage accounts for a big proportion of the total energy usage in buildings, there have been diverse researches and technological developments on solutions. As a solution to such a problem, light shelves as one of the lighting systems have been researched after being recognized its efficiency. However, the existing researches on light shelves focused only on the variables of light shelves and failed to reflect the consideration on spatial form, which is a variable of indoor spaces. In this regard, this research aimed to establish basic sources for light shelve design by obtaining optimal values for light shelves based on the performance evaluation on light shelves on inclined ceiling, a kind of the spatial forms. The research results are as follows: 1)As the spatial depth meeting the standard indoor lighting level of 400 lx is equally seen regardless of the establishment of light shelves, there are no improvements in efficient lighting performance but improvements in lighting performance when the maximum ceiling height of the inclined ceiling increases. 2) The indoor average lighting level is lower with the light shelves established in the spatial form of inclined ceiling, than without the light shelves, which is considered to be caused by the awnings of the light shelves. In addition, the increase in angle and the decrease in width tend to raise the average indoor illuminance level by reducing the awning surface. 3) The increase in the angle of light shelves increases the reflective surface, and this is helpful to improve lighting performance, as the increased angle tends to raise the uniformity ratio of illuminance by growing the amount of light flowed deep into the indoor space. 4) The optimal standard for light shelves on inclined, considering the winter solstice and vernal/autumnal equinox, is the width of 0.3m of active light shelves. This research is relevant as it established basic sources by conducting performance evaluation on light shelves in terms of the inclined ceiling form, winter solstice, and vernal/autumnal equinox. It is considered that further performance evaluations are required on various spatial forms.