Airside energy recovery is the process of transferring heat between a building's exhaust air to its ventilation air by passing it through an energy recovery device such as a rotating heat wheel or a fixed plate heat exchanger. In the summer, the temperature of the warmer, humid outside air is cooled before entering the air conditioning system, which reduces air conditioning system demand. In the winter, the cold outside air is warmed before passing through the air system heating coils, thus minimizing the heating system demand. All energy recovery ventilation systems require frost protection or defrost means in climates experiencing severe winter design conditions.


Airside Energy Recovery exists within the Air Systems page of loadmodeling.tool and can be modified within the Air System Details.

The Energy Recovery Type affects the frost control behavior of the system, along with the supply air outlet temperature control.

  • Rotary type heat recovery adjusts the rotation speed to control frost formation and the supply air outlet temperature.

  • Fixed Plate utilizes air bypass around the exchanger to control both frost and supply air outlet conditions.

The Frost Control parameter has four choices:

  • -- : stands for the default type, None

  • Exhaust Air Recirculation: dampers are used to direct exhaust air back into the system through the supply side of the heat exchanger when the supply (outdoor) air inlet temperature falls below a threshold temperature. When exhaust air is being recirculated, no supply (outdoor ventilation) air is being provided through the heat exchanger unit (which may not be acceptable depending on occupancy ventilation requirements).

  • Exhaust Only: this control cycles off the supply air flow through the heat exchanger for a certain period of time while the exhaust air continues to flow through the exhaust side of the heat exchanger. It is assumed that the supply air is bypassed around the heat exchanging.

  • Minimum Exhaust Temperature: the temperature of the exhaust air leaving the heat exchanger is monitored and the heat exchanger effectiveness is decreased (by slowing heat exchanger rotation or bypassing supply air around the plate exchanger) to keep the exhaust air from falling below the threshold temperature

Other Energy Recovery Inputs

  • Sensible Heating %: Effectiveness of sensible heat exchange at 100% capacity and ARI standard conditions for heating

  • Latent Heating %: Effectiveness of latent heat exchange at 100% capacity and ARI standard conditions for heating

  • Sensible Cooling %: Effectiveness of sensible heat exchange at 100% capacity and ARI standard conditions for cooling

  • Latent Cooling %: Effectiveness of latent heat exchange at 100% capacity and ARI standard conditions for cooling

  • Economizer Bypass: Yes or no. When yes, the recovery device is bypassed or off at times the air side economizer is active

  • Nominal Power [Watts]: The electrical power required to operate the energy recovery device. This can be for controls, and/or motors associated with the device

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