How to model both natural ventilation and HVAC system in the same building on OpenStudio?

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In DesignBuilder your primary control for preventing simultaneous heating/cooling/venting is via your indoor environmental set point controls i.e. set an appropriate dead band between your heating, cooling and natural ventilation temperature set points. There are additional options to fine-tune the mixed-mode control strategy such as placing limits on outdoor temperatures (too hot or too cold) for natural ventilation or to switch between simultaneous and changeover control types. I presume it works in a similar way in OpenStudio as both use EnergyPlus. There is a free online tutorial on these controls in the "calculated natural ventilation" tutorial on the DesignBuilder website here which might give you a better insight: https://designbuilder.co.uk/training/...