Why in Natural Ventilation is there "fan efficiency" ?
Hi there! I'm in OpenStudio -> Thermal Zones -> Zone Ventilation Design Flow Rate -> Natural Ventilation. I'm mooving this natural ventilation to the "zone equipment" of each thermal zone. Now, for this natural ventilation I'm setting data like schedules and air change per hour. My qyestion is: why are there in this section data like "fan pressure rise", "fan total efficiency"? I know that natural ventilation is just something like opening windows, why are there data to fullfill about fans? thank you