In an era where sustainability is paramount, the 2021 International Energy Conservation Code (IECC) introduces stringent guidelines to enhance the energy efficiency of buildings. One of the key components of this code is Section C403.5, which pertains to economizers. Economizers play a pivotal role in regulating cooling systems in buildings, contributing to energy savings and environmental conservation.

The 2021 IECC is more than just a set of rules; it's a commitment to a greener, more energy-efficient future. Section C403.5 of the code focuses on economizers, a crucial element of heating, ventilation, and air conditioning (HVAC) systems. In this blog post, we'll delve into the specifics of economizers as outlined in the code, their significance, and when they are required.



  • Chilled Water Systems: If your building employs chilled water systems, an economizer is required based on the total cooling capacity, minus the capacity provided by air economizers. Consult Table C403.5(1) for capacity thresholds.
  • Individual Fan Systems (Non-Group R Occupancies): For individual fan systems with cooling capacity equal to or exceeding 54,000 Btu/h (15.8 kW), economizers are obligatory.
  • Standards Compliance | Execution Plans | Constructability Reviews | Best Practices Review/Implementation
  • Limit on Supply Capacity: There's a cap on the total supply capacity of fan cooling units without economizers. It should not exceed 20 percent of the total supply cooling capacity in the building or 300,000 Btu/h (88 kW), whichever is greater.
  • Integration and Automation of Process | Customization | Documentation | Steel Framing


  • Climate Zones 0A, 0B, 1A, and 1B: Buildings in these climate zones are exempt from economizer requirements.
  • Limited Operation: Systems expected to operate less than 20 hours per week are exempt.
  • Heat Recovery Systems: Systems equipped with heat recovery mechanisms in accordance with Section C403.10.5 are exempt
  • VRF Systems: Variable Refrigerant Flow (VRF) systems installed with dedicated outdoor air systems do not require economizers.