Analytical tests for investigating the accuracy of lighting programs

To help potential users test and compare lighting computer programs, this paper defines some basic reference test cases with analytical solutions. These can be used to verify the accuracy and the capacity of lighting programs to correctly simulate different aspects of lighting calculations; daylight entry inside buildings, influence of incidence angle on glass transmittance, light distribution from luminaires having photometric files, inter-reflections between diffuse surfaces with influence of surface transmittance and finally daylight factor calculations under CIE overcast sky. To illustrate the use of these tests they were conducted with a software package available on the market, and the results compared with the analytical solutions. The tests demonstrate the software capabilities and limitations with regard to inter-reflection calculations, to simulation of luminaries and to daylight penetration through unglazed or glazed apertures.