An HVAC system for a building includes an airside economizer, a plurality of sensors, and a controller. The airside economizer includes a first air intake configured to receive return air from within a building, a second air intake configured to receive outdoor air from outside the building, and an air discharge configured to provide discharge air to the building. The controller is configured to identify a wet coil condition or a dry coil condition, calculate an enthalpy of the return air and an enthalpy of the outdoor air, select either a normal cooling mode or free cooling mode based on the calculated enthalpy of the return air, the calculated enthalpy of the outdoor air, and the identification of the wet coil condition or the dry coil condition, operate the airside economizer to provide the return air to the building as the discharge air in response to selecting the normal cooling mode, and operate the airside economizer provide the outdoor air to the building as the discharge air in response to selecting the free cooling mode.