Effect of Perimeter Balconies on Daylighting in Atria

Designers who predict daylighting performance usually assume that the space is empty and uncluttered. A careful understanding of the light reduction due to major architectural obstructions is necessary not just for providing optimal light level for intended tasks but for safety in the spaces. In the initial stage of the daylighting design process, the effect and light attenuation caused by major interior obstructions should be carefully considered in order to determine whether the light condition in spaces is adequate for the required tasks in a quantitative and qualitative manner. Atrium design must typically confront several specific issues concerning aesthetics, thermal conditioning, and lighting. From the viewpoint of the daylighting, the atrium concept allows the exploitation of daylighting by bringing natural light into the center of the buildings, thus enhancing a more even distribution of daylight. The configuration of perimeter balconies, however, are determined on the basis of the purpose of the perimeter space and the use of the building, which may defeat the primary daylighting advantages inherent in the atrium concept. The authors have developed insights and design guidance regarding the critical daylighting performance factors by evaluating the relative effect of various perimeter balcony configurations on illumination level and its distribution with different atrium geometries and wall reflectances. For these, parametric measurements of illumination level with a scale model of a four-sided atrium building and various perimeter balcony configurations have been conducted under diffuse sky conditions within the sky simulator at Texas A&M University. This paper represents the atrium performance results in terms of Daylight Factor, well index, balcony well index, the configuration of perimeter balcony, and perimeter reflectance; and the results are compared with basecase atria without any perimeter balcony.