The daylighting contribution in the electric lighting energy uses: EN standard and alternative method comparison

The standard EN 15193: 2007. Energy performance of Buildings. Energy requirements for lighting includes a comprehensive method, which takes into account the daylighting contribution in the calculation procedure. Such contribution is obtained through several approximations. An alternative approach is developed, where the daylighting contribution is based on the availability of outdoor illuminance data and an explicit procedure. The methods are tested on a standard office building, whose lighting requirements are calculated for different visual tasks, observation positions and climatic zones. The results show discrepancies among the methods and address the need of a more accurate estimation of the lighting energy service.