Section C403.7/Energy Recovery Ventilation Requirements
IECC C403.7 requires energy recovery ventilation (ERV/HRV) systems where outdoor air intake exceeds specified thresholds, recovering energy from exhaust air to reduce heating and cooling loads.
Energy recovery is required on fan systems with both mechanical supply and exhaust where the design outdoor air supply rate exceeds the threshold in Table C403.7.1, which varies by climate zone and percentage of outdoor air. In climate zones 3B through 8, systems with 5,000 CFM or more of outdoor air at 70% or more outdoor air require energy recovery. In climate zones 4 through 8, systems with 5,000 CFM or more at 30% or more outdoor air require recovery. The energy recovery device must have a recovery effectiveness of at least 50% of the difference between the outdoor air and return air enthalpy (or temperature for sensible-only recovery). Section C403.7.1 provides exceptions for systems with economizers and for systems where energy recovery is not cost-effective based on the climate zone and heating/cooling degree days. The recovered energy reduces the heating and cooling load that the HVAC system must handle, directly reducing energy consumption. The energy recovery device is typically a total energy wheel (rotary enthalpy exchanger), a plate heat exchanger, or a heat pipe, installed between the outdoor air intake and the exhaust air outlet of the air handling unit.
Why this section exists
In buildings with high outdoor air requirements (hospitals, labs, assembly spaces, restaurants), the energy needed to condition outdoor air can represent 30 to 60% of the total HVAC energy use. Energy recovery captures a significant portion of this energy from the exhaust air, which would otherwise be wasted, and transfers it to the incoming outdoor air. In cold climates, this preheats the outdoor air; in hot climates, it pre-cools and dehumidifies it. The 50% minimum effectiveness ensures the recovery device provides meaningful energy savings. The threshold values target systems large enough that the device cost is justified by the energy savings, while exempting small systems where the payback is unreasonably long.
What plan reviewers look for
Plan reviewers check the mechanical equipment schedule for outdoor air CFM and the percentage of outdoor air for each air handling unit. They compare the outdoor air quantity and percentage against Table C403.7.1 for the project's climate zone. For systems that exceed the threshold, they verify an energy recovery device is specified on the mechanical drawings or in the equipment schedule. They verify the recovery effectiveness is at least 50%. They check for the economizer exception where applicable. They verify the energy recovery device is shown on the air handling unit schematic with the supply and exhaust air paths. They confirm compliance with ASHRAE 62.1 ventilation rates are maintained through the recovery device.