Simulation-based Assessment of Two Different Daylight Requirements: Daylight Factor and LEED 2.2

Daylighting is an essential technique for realizing green and sustainable building design to ensure occupant comfort. Although the benefits of daylight are widely acknowledged, daylight-related issues have not been addressed in preliminary building design. In order to assess and predict daylight performance, we can select two different requirements: daylight factor (DF) and LEED 2.2 daylight requirement. The minimum recommended DF is over 2% and LEED 2.2 requires that a minimum daylight illumination of 25 footcandles (FC) be achieved in at least 75% of all regularly occupied areas. Therefore, in this paper, we provide a simplified method to evaluate the daylight performance necessary to meet these two daylight requirements. Based on a series of computer simulations using RADIANCE, the main results obtained contained fenestration criteria to meet daylight requirements including DF and LEED 2.2 (area percentage over 25 FC). Moreover, regression models and simple evaluation tools can be developed to correlate the two daylight requirements and fenestration parameters such as window area, visible transmittance (VT), and regularly occupied area. This can be used as a pre-design tool not only to obtain more credits in LEED 2.2 green building rating systems but also to evaluate DF that meets the recommended level.