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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).

Fan Power Budget

This measure seeks to reduce energy used in building air distribution systems through reducing pressure drop in fan systems (through high performance ducts) and requiring minimum efficiency standards for certain types of fans. More specifically, the high-performance ducts and fan systems measure seeks to significantly revise the existing fan power limitations in Title 24 Part 6 and require a minimum Fan Energy Index (FEI) level for certain fan types. This measure largely adopts a recently adopted ASHRAE measure (Fan Energy Index, adopted into ASHRAE as Addendum AO in 2019) and an ASHRAE measure currently under consideration to revise the fan power limitations. Together, these two components of this measure will require most fan systems which move conditioned air be subject to a new fan power budget (prescriptive) and will require minimum FEI efficiency levels for certain fans (mandatory). The high-performance ducts component of this measure (via a new fan power budget methodology) will apply to new construction, alterations and additions in the same manner the existing fan power limitations currently apply within Title 24 Part 6 Section 140.4.  This will require changes to the ACM and the compliance software.  

These changes are summarized below.  

In this proposal, the Statewide CASE team proposes to replace the fan power limitations with a new fan power budget methodology. The significant changes include: 

  1. Changing the input measurement from fan brake horsepower or motor horsepower to fan electrical input power to capture transmission and motor efficiency losses. The fan power budget electrical input power calculation is based on the Air Movement and Controls Association (AMCA)-208-18. 
  2. Creates new budget pressure tables such that the pressure allowances are calculated for each fan system, where allowances are dependent on air flow and system design and included components in the air system.  
  3. Creating new definitions of various fan systems and clarifying that fan power budget calculation must be performed for each fan system: 
    1. Supply fan systems 
    2. Exhaust/Return/Relief fan systems 
    3. Transfer fan systems 
  4. Expands the scope of fan systems covered by code from 5 motor nameplate horsepower to 1 kW fan electrical input power from. 
  5. Requires each fan and fan array that is not part of a manufactured assembly (i.e. stand-alone fans) greater than 1.0 hp or with a combined fan nameplate electrical input power greater than 0.89 kW to have an FEI of 1.00 or higher, per AMCA 208. 
  6. Healthcare exemption is removed, meaning healthcare facilities will be subject to fan power requirements for the first time.

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 largely on the recently adopted Addendum AO to ASHRAE Standard 90.1-2016 and requires each fan and fan array that is not part of a manufactured assembly (i.e. stand-alone fans) greater than 1.0 hp or with a combined fan nameplate electrical input power greater than 0.89 kW to have an FEI of 1.00. T 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.  

The FEI component of this measure will be mandatory and will only apply to new construction, not alterations or additions. This measure will not require changes to the ACM and the compliance software.  

Duct Leakage Testing

During the first utility-sponsored stakeholder meeting, which was held on November 5, 2019, the Statewide CASE Team presented an potential code change proposal to require leakage testing of entire air distribution systems. As of January 1, 2020, the California Mechanical Code (CMC) requires substantial changes to Title 24, Part 4 controlling duct leakage. Both testing and allowed level of leakage for all ducted systems are established by Section 603.10.1 of the CMC. The section states, “Representative sections totaling not less than 10 percent of the total installed duct area shall be tested. If the 10 percent fails to meet the requirements, 40 percent shall be tested. If the 40 percent fails, 100 percent needs to be tested. The duct work must meet Leakage Class 6. The Statewide CASE Team is developing clarifying language in the reference appendices of Title 24, Part 6, detailing how the testing is to be executed, as well as compliance documentation.  

The Statewide CASE Team is also proposing mandatory requirements of Seal Class A for all ductwork and VAV box leakage certification by ASHRAE 130 or field testing by the SMACNA System Air Leakage Test Manuals. This proposal aligns with the sealing requirements in ASHRAE 90.1.  

Relevant Documents

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

Round Two Utility-Sponsored Stakeholder Meeting Materials

Round One Utility-Sponsored Stakeholder Meeting Materials

Provide Feedback

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.


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.

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