A COMPARISON OF WINDOW MODELING METHODS IN ENERGYPLUS 4.0
Peter Lyons, Justin Wong, Mahabir Bhandari
EnergyPlus Version 4.0 (U.S. Department of Energy, 2009) offers several powerful, alternative methods for defining windows and other fenestration systems in modeled buildings. Recently, a new ‘Simple Window Model’ was added to EnergyPlus. This tool allows the user to define a vertical window in an EnergyPlus building model using only the window’s whole-system U-factor, solar heat gain coefficient and (optionally) its visible transmittance. The Simple Window Model involves approximations which may lead to errors in some situations. This study presents a comparison and evaluation of several current, alternative methods for defining and modeling windows in EnergyPlus. We also briefly draw attention to the effect of using different weighting functions for the solar spectrum. In a case study, a simple 10-storey, 5-zone per storey, office building was modeled. Results from three window-modeling methodologies are compared, conclusions are drawn and recommendations are presented.
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