Modeling windows in EnergyPlus

We give an overview of how windows are modeled in the EnergyPlus whole-building energy simulation program. Important features include layer-by-layer input of custom glazing, ability to accept spectral or spectral-averaged glass optical properties, incidence angle-dependent solar and visible transmission and reflection, iterative heat balance solution to determine glass surface temperatures, calculation of frame and divider heat transfer, and modeling of movable interior or exterior shading devices with user-specified controls. Example results of EnergyPlus window calculations are shown.