Hi @MaxMarschall ,
Yes, the Ideal Air System will continue to supply the minimum outdoor air requirement even when the windows are open since there’s no guarantee that the windows are open enough to meet that requirement. You can tell the system to stop supplying that minimum outdoor air using a ventilation_sch_ and the HB Apply Room Schedules component. But, when the room is in between heating/cooling setpoints like that, the outdoor air isn’t heated or cooled when it’s brought in by the system so I would doubt that you’d see much of a change by using the ventilation schedule.
7% savings with a 24C cooling setpoint is actually pretty good in my experience and I’m almost a little surprised it’s that large when you aren’t changing the cooling setpoint. I would recommend that you change this cooling setpoint because we know that PMV does a poor job at evaluating thermal comfort in naturally ventilated buildings and, as the Adaptive Model illustrates, occupants will likely desire warmer indoor temperatures if the average monthly conditions are warm and they have the freedom to open the windows. If you ask me, I think this change in comfort models is where the vast majority of energy savings from naturally ventilated buildings comes from. As you see with your simulation here, if you don’t account for this comfort model change, the operable windows really aren’t much different than the air side economizers that we already put into most air-based HVAC systems these days.
Depending on the climate, I think you can boost the cooling setpoint up to something like 27C-29C if you want to account for the behavior and desires of occupants under the adaptive model.