The Fan Energy Index changes how we think about fans

Fans are everywhere in our buildings, but they mostly exist so we don’t have to think about them. When working properly, fans become the white noise of indoor spaces; we only tend to notice them when we’re uncomfortable.

Perhaps because we tend to ignore them, fans have historically felt a cool reception when it comes to energy efficiency. In much of our emerging technology research, we evaluate new, exciting gizmos and concepts to determine their potential energy savings. When it comes to fans, however, the technology hasn’t really changed. Motor, blades, rotation – that’s pretty much it. Technologies such as variable frequency drives do achieve some energy savings, but surely there are opportunities for fans to do better.

As it turns out, there are. Recently, the savings potential of standalone fans has heated up thanks to a new method in which we choose the proper fan to use in a situation.  As with other performance-based measures, we can achieve energy savings by setting a specific efficiency goal based on the building’s unique conditions. Once we know exactly what a fan needs to accomplish, we can select the best fan to meet that target.

Meet the Fan Energy Index

The improvement comes in the form of the Fan Energy Index (or FEI), a metric first developed by the Air Movement and Control Association. Under the new metric, a fan manufacturer provides a matrix of various FEI numbers, each based on the combination of factors such as pressure (PSI) and flow rate (CFM). Some fans might excel in low-pressure, high-flow situations, but that doesn’t mean they’ll work as efficiently under high pressure. The Fan Energy Index tells you the situations in which a fan might excel and, likewise, when a different fan might be a better choice.

Conversely, under the most common existing metric, known as the Fan Efficiency Grade (or FEG), a designer might select a fan based on a set efficiency metric at a condition that may not apply. For example, let’s say a designer chooses a fan based on its standard FEG, which says it is 92% efficient. However, when applied to the actual conditions of the building, the fan only operates at 80% efficiency.

The Fan Energy Index seeks to correct this problem by tackling the problem in reverse. Under FEI, a designer looks at the application intended for the fan and, based on the pressure and flow rate, selects a fan with a FEI that meets those specific conditions. This time, the fan does indeed operate at 92% efficiency – all because we selected the fan based on the building’s specific needs.

What’s next for the Fan Energy Index?

In 2021, the Fan Energy Index will likely find its way into building codes. We expect the new codes around standalone fans to be made public in the summer of 2021, after which it will be up to jurisdictions whether to adopt them.

At Slipstream, we have been conducting research for a major Midwest utility to evaluate the Fan Energy Index and determine the applications in which it can make the biggest impact on energy efficiency. Combining our technical experience with data analysis, we aim to provide practical guidance around FEI implementation, including:

  • The best FEI applications to make the biggest energy-savings impact
  • Advice for designers who are selecting the fans
  • Advice for fans distributors and vendors
  • Which building sectors have the most promise
  • What the typical cost might be for building owners

When our research is complete, we expect to use these results to help developers, designers, and utilities prepare to put the FEI into practice. For now, we feel it’s important to educate building operators, facility managers, and designers on the big changes that will soon be blowing their way.

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