Why exhaust fan use causes heating and cooling energy needs?

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Hello! I am trying to simulate an exhaust fan in a single-zone building. Infiltration is used to compensate for the exiting air. The building has also an ideal load air system, whose internal node is used as an inlet node for the exhaust fan object. However, despite keeping the heating and cooling off (by setting proper thermostat values), output variables "Zone Air System Sensible Cooling Energy" and "Zone Air System Sensible Heating Energy" present positive values. Any ideas why this happens and how to override it?