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Nonresidential Air Distribution

Measure Description

This CASE Report will reduce the energy consumption of space conditioning fan systems in nonresidential buildings by both reducing static pressure in air ducts and adding a new metric that allows for more efficient fan selections. This includes three submeasures: high performance ducts/updates to fan power limits, improved fan efficiency metric, and expand duct leakage testing. Measures are modeled after standards developed, or in consideration, by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE).

High performance ducts/updates to fan power limits

The fan power limits were updated in Title 24-2019 and will take effect January 1, 2020. This measure proposes to reform fan power limitmethodology and increase the stringency of prescriptive efficiency requirements for fan systems in nonresidential buildings. Reduced fan power consumption can be achieved by reducing the static pressure in air duct systems, (2) reducing pressure drop through system components, such as filters, or (3) employing higher efficiency fans, motors, and transmissions.  

In this proposal, the Statewide CASE team improves the fan power limits by: 

  1. Including fan transmission and motor efficiency by changing input measurement from fan brake horsepower to fan electrical input power. The budget fan electrical input power calculation is based on the Air Movement and Controls Association (AMCA)-208-18, and budget pressure losses to determine budget fan power for each fan system. 
  2. The boundaries of fan systems are clearly defined with the addition of definitions for: 
    • Supply fan systems 
    • Exhaust/Return/Relief fan systems 
    • Transfer fan systems 
  3. Clarifies the requirement to use VAV system pressure drop values. 
  4. Reduces the threshold for fan system compliance to 1 kW fan electrical input power from the current 5 shaft brake horsepower. 

Fan Energy Index

This submeasure proposes to implement a new efficiency metric for certain fans in the Title 24, Part 6 code language by requiring certain fans meet a minimum Fan Energy Index (FEI) at the design conditions. This measure is based in part on the recently adopted Addendum AO to ASHRAE Standard 90.1-2016 which sets an FEI of 1.0 for most fans generally not in packaged equipment (e.g. supply, exhaust fans, etc.) and an FEI of 0.95 for variable air-volume fans.  The CASE Team is also considering higher FEI levels, such as those currently being considered in the ASHRAE 189.1 standard process where the FEI for most fans would be 1.1, or 10% more stringent than the 90.1 language. The FEI is an efficiency metric created by the Air Movement and Control Association (AMCA), an organization that sets standards for commercial and industrial air movement equipment. The metric and subsequent standards to develop FEI ratings have been pursued in collaboration with the Department of Energy and energy efficiency advocates, which started during a now-stalled federal rulemaking to develop commercial and industrial fan efficiency standards. FEI addresses a longstanding problem in characterizing fan efficiency; a fan’s peak efficiency is often poorly correlated with its actual efficiency in typical operating conditions. The FEI metric is an easy method to encourage mechanical designers to make fan selections closer to a fan’s peak efficiency, where the higher the FEI, the less energy is consumed.  

Expand Duct Leakage Testing

New prescriptive duct leakage requirements for nonresidential buildings that utilize VAV supply-air systems running through ceiling-plenum returns, toilet exhaust systems, and general exhaust systems. In all three cases, ductwork will be required to meet Sealing Class A. VAV supply-air duct systems will be required to not exceed leakage rates of 4 percent upstream, plus 4 percent downstream of the VAV boxes. Exhaust duct systems will be required to not exceed leakage rates of 6 percent. Testing requirements will be based on either ANSI/ASHRAE Standard 215-2018: Method of Test to Determine Leakage of Operating HVAC Air Distribution Systems or the SMACNA System Air Leakage Test (SALT) Manual for VAV supply-air systems and ASTM E1 554, SMACNA SALT Manual, or SMACNA Air Duct Leakage Test (DALT) Manual for exhaust systems.

Provide Feedback

Participate in the Utility-Sponsored Stakeholder meeting for this topic on November 5, 2019 ! View the event here.

This measure description will be updated as research is developed to support the 2022 code cycle. For questions or suggestions, email Include the measure name in the subject line.


Relevant Documents

Measure proposals, supporting documents, and other outside references will be made public as they become available.


Give Us Your Feedback

The Statewide CASE Team values input from all stakeholders engaged in the Title 24, Part 6 code change process. We encourage the open exchange of code change comments and concerns.

  • Use the form above to provide feedback on this measure.