Fan Energy Index Comes to 2021 International Energy Conservation Code

In the 2021 edition of the International Energy Conservation Code, fan energy index replaces fan efficiency grade as the metric for fan-efficiency provisions.

The ratio of the electrical input power of a reference fan to the electrical input power of an actual fan at a given duty point (airflow, pressure and air density), FEI considers motors and drives, not just fans, which makes it consistent with new efficiency metrics for pumps and air compressors. The higher the FEI rating, the more efficient a fan will be for a given duty point. This allows engineers to perform return-on-investment analyses for different fan types, sizes and motor/drive combinations when designing systems.

The 2021 IECC requires that FEI ratings be third-party certified. AMCA International, which formalized FEI in ANSI/AMCA Standard 208-18, Calculation of the Fan Energy Index, has been certifying FEI ratings since 2019. Nearly 300 fan models are FEI certified, mostly through AMCA certification of manufacturer sizing and selection software.

FEI previously replaced FEG in ANSI/ASHRAE/IES 90.1-2019, Energy Standard for Buildings Except Low-Rise Residential Buildings. Like that standard, the 2021 IECC increases the scope of the fan-efficiency provision by lowering the minimum size of covered fan systems from 5 horsepower to 1 horsepower and removing the exemption for powered roof ventilators. For more information, visit

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