Since this is an early stage to schematic design tool, splitting into zones does not make sense since interior program is assumed to have the same temperature. Many academic papers have shown the conclusions from simulations of single zone vs perimeter/core are the same for this level of detail. Not having zones allows us to accept geometry that is not 100% closed, allowing messy models from conceptual design to be analyzed easily. We have observed that many typical Revit, Rhino, and Sketchup models are not constructed with closed rooms making many geometry exporters send over bad data into an energy modeling tool. Our goal is to have the most accurate method with the least junk data to make the best decisions.