How to model gravity ventilators in Design Builder

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We have a set of building plans that show a very large exhaust fan and gravity ventilators installed. I believe the design intent here is for the exhaust fan to run and create negative pressure, and the gravity ventilators would open to allow fresh air to infiltrate the building. Are there any recommendations for how to model gravity ventilators in DesignBuilder? I was thinking of using roof vents and having the schedule match the exhaust fan schedule, but I am not sure if this is the correct approach (and whether DB accounts for pressure with natural ventilation setting turned on). I have never turned natural ventilation on before...