FEI: How Adoption of IECC 2021 and ASHRAE 90.1 2019 Impacts the Selection of Efficient Fans

The FEI (Fan Energy Index) Metric has been implemented into IECC-2021 and ASHRAE-90.1 2019 which was adopted by the state of Massachusetts in July of 2023. FEI measures the efficiency of the entire fan system, including the fan, motor, and drive using data from laboratory performance tests. By offering a range of complaint, operational efficiencies, FEI allows design engineers to make more precise, energy-efficient fan selections tailored to specific conditions.

Previous methods of selecting an efficient fan were based on the fan shaft input brake horsepower or the fan’s efficiency at a required duty point (CFM and static pressure). Neither of these methods considers the power loss due to the fan’s motor and drive inefficiency. If reducing electric energy consumption in fan applications is of concern, it makes sense to compare the electrical power input of one fan selection to another. The FEI metric assists you in doing just that—selecting the fan with the lowest input electrical power consumption. The FEI metric includes electrical power input to the fan system including the efficiency impact of the motor and drive.

Regulatory authorities such as the U.S. Department of Energy and local energy codes based upon current energy standards (IECC, ASHRAE 90.1, ASHRAE 189.1, IgCC, CEC Title 20, etc.) state that applicable fans have an FEI of 1.0 or greater. Manufacturers that have fans with FEI-certified ratings listed in accordance with AMCA 210 can present FEI data for several fan sizes with the same application duty point (flow, pressure) in tabular form.

In addition to overall fan efficiency, by optimizing FEI, the fan selection ends up being more central in the fan curve. This provides the design engineer more comfort against unforeseen static pressure impacts in the field. A less efficient fan may be selected closer to the max RPM line on the curve and could result in underperformance if the actual static pressure exceeds what was calculated during the design.

Lastly, you will notice that the FEI increases as the fan speed goes down. This can often translate to quieter fan operation as well. This is additional protection for the design engineer (and building occupants) against unwanted noise levels in sound-sensitive applications.

Greenheck includes FEI metrics on applicable fan products in eCAPS online product selection program and its suggested that design engineers incorporate FEI values on their fan equipment schedules.