Lighting is typically the largest single energy use in a non-residential building—approximately one-third of the total. The design goal should be a building that uses daylighting with electric lighting as a backup. The analysis for the daylighting takes the weather file, glazing materials, adjacent surfaces and any overhangs, and adjacent ground reflectance assumptions and performs an hourly simulation of the natural daylighting potential for each space within the model with either windows and/or skylights.