Daylight Performance Evaluation of Atrium by Transformation in Freeform Type

The aim of this research was to examine the correlation between the performance of daylight and geometry of FREEFORM atrium. In consideration of the solar environments that have the greatest effect on the atrium, categorized and classified types of transformations were introduced. Atrium classification defined by vertical axis, plan scale and rotation is used to determine the transformation and the type. Several atrium cases, characterized by a different form or shape, were analysed by simplified methodology to predict DF(daylight factor), direct sunlight area and Uniformity Ratio on the atrium floor, through computer simulation by Ecotect and Radiance. Simulation programmes were used to simulate square, four-sided, top-lit atria under overcast and clear sky conditions. This study has investigated the effect on daylight performance of the geometric characteristics of atrium such as PAR, distance, translation vector, types of curve, height and angle. From the results, the design guidelines are proposed as follows. All types show a decrease of light influx and increase of UR as the atrium height increases. The height of atruim, therefore, should be considered first regardless of form class or the variables of atrium. Performance shows a big difference according to the light direction if certain transformation is made along a direction. It is maximized when the transformation aligns to the direction of light and converges to the rectangular shape with low PAR. There is a decrease in performance under the environment of lights from all directions like Overcast sky.

아트리움의 비정형적 변형에 따른 채광성능 평가에 관한 연구