Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
Sounds like you need to model an exhaust only ventilation system. You can add a zone exhaust fan, and set it to run when air speed is zero with a Schedule:File object that you calculate from the weather file, or alternatively, if you want to do this for several buildings / weather files, write some EMS code to toggle the fan availability based on an outdoor air speed sensor.
For natural ventilation if your project is more than one zone (airflow happens across multiple zones), you'll need to use the Airflow Model Network objects, which are documented here
