Daylight Prediction: An Evaluation of Daylighting Simulation Software for Four Cases

July 29, 2015
Poster Session — President’s Hall 2
4:00 pm  -  7:00 pm

The use of daylighting to supplement and offset artificial lighting requirements in interior spaces is an important step in achieving California’s current and future energy goals. The analysis of daylighting is not only difficult for lighting designers, but also the results are not always accurate. Four popular lighting analysis software programs (AGi32, Ecotect/Radiance, Rhino/Diva, and Rhino/Grasshopper/Honeybee) failed to provide results that matched the data gathered in physical models and from calculations based on the laws of physics for the Specular Reflection Test, Reflectance Test (Namburi 2006) and Luminous Flux Conservation Test (CIE 171:2006).The results recorded for most of the simulations have shown more than 20% variation (the threshold for validation tests according to CIE), between the software packages and real data.

Additional parameters, such as the clarity of the Graphical User Interface (GUI), time and training required for full use, quality of scene renderings, ability to calculate climate-based metrics and code compliance, and interoperability with other software have been compared across the same software programs and the results tabulated. The tabulation also lists the critical nuances for daylighting simulation in each of the four software programs. This together with a narrative describing the change of metrics used in digital daylight simulation will help designers analyze their buildings more accurately.

Hypothesis: AGi32, Ecotect/Radiance, Rhino/Diva, and Rhino/Grasshopper/Honeybee cannot consistently and accurately simulate the physical properties of daylight for Specular Reflection, Reflection, and Luminous Flux Transmission Test.