Analysis of the accuracy of the sky component calculation in daylighting simulation programs

The main aim of this article is to analyze the precision of several lighting simulation programs regularly used in daylighting studies for architecture, following the methodology established in the CIE test cases document. The 3DS Max Design 2014, Daylight Visualizer 2.6, DaySim 3.1b, Design Builder 3.0, Dialux 4.8, Ecotect Analysis 2011, Lightscape 3.2 and Relux Pro programs are analyzed. In order to establish the precision for each program, the sky component is measured at different points of study on the floor of a room, taking variable sizes and positions of openings into consideration. The results are contrasted with the analytical calculation of the sky component using Tregenza algorithms and the test cases established by the CIE, considering the models for Traditional and Standard Overcast Sky. Following the analysis of the sky component using the CIE test cases, it is concluded that the 3DS Max Design 2014 and Daylight Visualizer 2.6 programs present a maximum relative difference from the analytical model of close to 10%, while the DaySim 3.1b, Dialux 4.8 and Lightscape 3.2 programs show a margin of relative error lower than 30% in all case studies. Design Builder 3.0, Ecotect Analysis 2011 and Relux Pro show inadequate results.