It sounds as though you are using the correct “tools” in EnergyPlus.
Report the zone temperatures during the unoccupied periods and compare to the zone setpoint. If the temperature does not exceed the setpoint in the cooling season or fall below the setpoint in the heating season, then the fan should remain off.
p.s., EnergyPlus assumes that a zone is in the “occupied” period whenever any people are present. If your People object schedule shows non-zero values (e.g. 0.02), then it is an “occupied” period.
James V Dirkes II, PE, BEMP, LEED AP
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