2016 Volume 81 Issue 727 Pages 1917-1927
This paper studies the characteristics of indexes and criteria related to the daylighting evaluation which is applied to architectural design in Japan. The paper further on clarifies the current situation of daylighting evaluation and the prospects for the future.
As for the index concerning daylight acquisition and discomfort glare, this paper illustrates their historical development from its very first introduction to the most recent. By tracing it's development in chronological order, the paper demonstrates the extension of the evaluation contents and enables to distinguish one index from another. Although none of the existing index is perfect, understanding its limitations and characteristics can influence the architectural design. Regarding daylight acquisition, several indexes such as DA and UDI, which are based on annual simulation, had been introduced. These indexes contribute towards designing efficient lighting system including automated blind control and artificial lighting in response to the fluctuation of natural daylight. As for the measurement of discomfort glare, indexes such as PGSV and DGP had been introduced to control the real-time automated blind control system in response to signals from sensors and the image analysis technology. By looking at the development process, the evaluation methods are generally upgraded over time as the indexes are modified in accordance with the introduction of new technology. However, the latest indexes lack numerical standards to evaluate the performances of buildings and thus it is crucial to set up the standard for these indexes.
As for the criterion, this paper clarifies the current evaluation system for daylighting mainly focusing on Japanese laws, standards, and the green building certification programs. The current Japanese Building Code regulates the minimum daylight acquisition, but other standards used in Japan, such as the JIS and AIJES are not adequate enough for a comprehensive evaluation of daylighting and visual comfort. The green building certification program, CASBEE does not have the appropriate system to evaluate performance by the computational simulation compared to other foreign leading green building programs like LEED or BREEAM. The standards must change in the near future to represent clear criteria for a comprehensive evaluation of daylighting and visual comfort. The criteria and evaluation must also include the daylight acquisition and the discomfort glare, and must be able to present designers with an appropriate numerical goal. In regard of CASBEE, it is strongly desired to keep up the rapid development of analysis technology, sensing technology and the evaluation indexes, by revising constantly and consistently.
