A Comparison of the Latest Window Modeling Methods in EnergyPlus

The accuracy and sensitivity of fenestration modeling in EnergyPlus (DOE 2019) is very important since fenestration is typically the dominant envelope load. New technologies, such as room-side low-E coatings and vacuum glazing, can challenge models that were developed before these technologies existed. In this report, we examine the sensitivity of EnergyPlus results to six available window models, including two simplified models that utilize known overall U and SHGC of the window (simple bulk properties) and creates layer-by-layer descriptions for fenestration system. One of these simplified methods also takes into account the type of frame and number of glazing layers if available. A range of window performance levels are modeled with the residential prototype buildings developed by Pacific Northwest National Laboratory, based on DOE's Residential Reference Building Models. Building models include high- and low thermal mass versions to understand the sensitivity of results to fenestration solar transmittance variations. Results from six window-modeling methodologies are compared, conclusions are drawn, and recommendations are presented.