Efficient Calculation of Annual Daylighting Performance Metrics Using the Klems Grid

Natural lighting (daylight) plays a decisive role in energy saving and building maintenance. An important aspect is the comfort of the premises. Modern building design requires computer analysis of indoor illumination in accordance with the green building certification program, the main indicators of which are spatial daylight autonomy (sDA) and annual sunlight exposure (ASE). Calculation of these metrics requires thousands of simulations of global illumination for various time moments throughout the year. Well-known methods of lighting simulation are not effective here. We propose an original approach that uses precomputed data and its fast interpolation on a Klems grid to iteratively simulate the lighting distribution. The method was compared with classical stochastic ray tracing and existing solutions based on the radiosity method. The efficiency of calculations has increased significantly (and sometimes orders of magnitude) while maintaining high accuracy of the results. The ability to calculate metrics in tens of minutes on a regular computer, provided by our method, allows an architectural design to be continuously checked for compliance with the green buildings program.