Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
In DOE-2, operable windows are modeled as natural ventilation in SYSTEM using the Sherman-Grimsrud Infiltration Model (when I asked the author Max Sherman whether this was an acceptable use of his model, Max said it was actually better suited for large bulk flows than through small cracks and leaks!). S-G is a single-zone model, so there's no capability to model air flow from zone to zone, as is possible with network models. However, at the single-zone level it uses similar physics with a wind-driven and a temperature driven component. For many years, natural ventilation was allowed only with the RESYS (residential) system, but starting with 2.1E it was also made available to other air systems. The amount of window openings is entered as a FRAC-VENT-AREA, and controlled using either the temperature or enthalpy difference between indoors and out. One thing I've like about the control is that it first tests if natural ventilation can hold the setpoint, and if not, it then models the windows as closed and simulates the A/C.
