Comparative Analysis of Prediction Accuracy from Daylighting Simulation Tools

ABSTRACT

In this article, a validation analysis of predictions from selected daylighting simulation capabilities is presented. The daylighting simulation tools considered in the study include EnergyPlus Detailed, EnergyPlus DELight, DAYSIM, and SPOT (Sensor Placement and Orientation Tool). The National Research Council of Canada provided detailed site and sensor data for an experiment recording daylight exposure throughout a side-lit private office space using various daylighting strategies. The site information provided included geometry of the space and daylighting test cases through detailed SketchUp models. Reflectivity and transmittance properties of experiment surfaces and windows were well documented to enable accurate replication in daylighting models. On-site weather data were also collected to allow the test environment to be repeated. Illuminance measurements at 5-min intervals at 12 sensor locations within the space allowed computer simulations to be thoroughly tested. The three daylighting test cases chosen for the validation study, no daylighting device, interior light shelf, and exterior horizontal blinds, were selected to test each software’s ability to model direct sunlight, interior obstructions, and exterior reflections. Through graphical observation and statistical measures DAYSIM was determined to be the most accurate overall. However, it is important for users to consider the intended application of the daylighting software selected. Depending on the daylighting conditions, facade construction, and sensor location, other software performed equally well. Each of the studied software also has other features such as photosensor modeling, integration with thermal simulations, and occupancy predictive models that must be weighted when selecting the appropriate daylighting software for your application.

KEYWORDS:

• daylighting simulation
• daylighting validation
• DAYSIM
• EnergyPlus DELight
• EnergyPlus Detailed
• SPOT