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Proposal Based on ASHRAE 90.1-2016

Nonresidential HVAC

Codes and Standards Enhancement (CASE) Report

The Statewide CASE Team is requesting feedback on the 2019 Title 24, Part 6 Draft CASE Reports. The CASE Report presents pertinent information that supports the code change proposal. Please email feedback to You may also submit written comments to the Energy Commission. See the agenda for Energy Commission pre-rulemaking workshop (available here) for instructions on how to submit comments to the Energy Commission’s docket.

Draft CASE Report: Proposals Based on ASHRAE 90.1t


Measure Description

This report includes the Statewide CASE Team’s recommendations to adopt requirements included in ANSI/ASHRAE/IES Standard 90.1-2016 — Energy Standard for Buildings Except Low-Rise Residential Buildings (ASHRAE 90.1-2016) in Title 24, Part 6. The Statewide CASE Team recommends that the seven measures described below are adopted into Title 24, Part 6.

Fan System Power (1 of 7)

The proposed Fan System Power measure will change the prescriptive requirements of Section 140.4(c) to harmonize with the calculation methodology to determine the allowed fan power with the methodology used in ASHRAE 90.1-2016 Section The ASHRAE 90.1-2016 calculation methodology was used as starting point for the California proposal, but adjustments were made to match the fan power allowance documented in the 2016 Title 24, Part 6 Nonresidential Alternative Compliance (ACM) Method Reference Manual. ASHRAE 90.1-2016 includes fan adjustment factors to allow for variability in allowed fan power for certain applications. The fan adjustment factors for process equipment will be incorporated into Title 24, Part 6.

Exhaust Air Heat Recovery (2 of 7)

The proposed Air-to-Air Heat Recovery measure will incorporate a new prescriptive requirement for exhaust air heat recovery. The proposed requirements for Title 24, Part 6 are based on the requirements in ASHRAE 90.1-2016 Section, but the minimum energy recovery ratio requirements in ASHRAE 90.1-2016 were adjusted to establish more appropriate requirements for California’s climate.

Equipment Efficiency (3 of 7)

The Equipment Efficiency measure will update the mandatory efficiency requirements for space conditioning equipment that appear in Tables 110.2-A through K of Title 24, Part 6. The revisions will harmonize the minimum equipment efficiency requirements in Title 24, Part 6 with the minimum efficiency requirements that were revised for the 2016 release of ASHRAE 90.1. Tables 110.2-A through K include efficiency requirements for a wide variety of space conditioning equipment and contain hundreds of unique efficiency values. The Statewide CASE Team is proposing that 19 values in these tables be updated. Most of these changes will update the minimum efficiency values for equipment that is already covered by Title 24, Part 6.

Federal law directs the United States (U.S.) Department of Energy (DOE) to review the federal minimum efficiency requirements for certain commercial and industrial equipment whenever ASHRAE 90.1 amends its standards for such equipment (42USC 6313(a)(6)(A)). As a result of the “ASHRAE Trigger” requirements, ASHRAE has taken the lead on updating equipment efficiency requirements for space conditioning equipment, and the DOE typically adopts ASHRAE’s equipment efficiency levels. States have a unique opportunity to adopt the equipment efficiency values that appear in ASHRAE 90.1 using a simplified process. The Energy Commission is not obligated to adopt ASHRAE 90.1 equipment efficiency values into Title 24, Part 6, but if Energy Commission chooses to do so, it can adopt the equipment efficiency values without conducting a cost-effectiveness analysis. The Energy Commission can adopt the efficiency values before the DOE completes their cost-effectiveness analysis and before the DOE adopts the standards. Given that the DOE rulemaking process is typically slower than the Energy Commission’s rulemaking process, this essentially means that California can adopt the equipment efficiency regulations several years earlier than the federal requirements will take effect.

Waterside Economizer (4 of 7)

Title 24, Part 6 requirements for waterside economizers have remained unchanged since 1998. The standards for waterside economizer are lacking in clarity/detail, and the economizer hours are lower than they should be for efficient operation. The proposed code changes are based on requirements in ASHRAE 90.1-2016, but some of the requirements in ASHRAE 90.1-2016 have been tailored so they are better-suited for California’s climate. The proposed code changes will provide more explicit requirements for waterside economizer, including:

  • Requiring integrated waterside economizer;
  • Establishing limitations on pressure drop of heat exchangers used for waterside economizing;
  • Adding a requirement that cooling towers must return to standard operation when not running economizer; and
  • Adding economizer requirement for chilled water systems that do not use large air handling units (affects passive “without fan” systems above a certain capacity).

The proposed requirements for Title 24, Part 6 will require more waterside economizer hours relative to ASHRAE 90.1-2016, a change that is intended to ensure economizers are utilized appropriately in California’s relatively dry summer climate. A maximum system approach of 5°F for waterside economizers is proposed, and a requirement that the system runs in full economizer mode at 49°F wet-bulb, compared to the previous requirement of 45°F wet-bulb.

Transfer Air for Exhaust Air Makeup (5 of 7)

This prescriptive measure will expand the existing Title 24, Part 6 requirement for kitchen exhaust transfer air to other types of exhaust systems, such as restroom and lab exhaust. This measure exactly matches the same requirement that was added to ASHRAE 90.1 in 2013. It is a prescriptive measure that applies to most spaces that have a process exhaust airflow rate that exceeds the airflow required for heating or cooling and that are adjacent to spaces that do not have high exhaust requirements. This will eliminate the wasteful practice of providing 100 percent outside air or 100 percent supply air to spaces with high exhaust rates while at the same time relieving air from other spaces in the same building, when the relieved air could have been transferred to the high exhaust space to reduce the total heating/cooling load

The payback for this measure is immediate because it reduces both first cost and energy cost compared to 100 percent supply air to spaces with high exhaust rates.

Demand Controlled Ventilation for Classrooms (6 of 7)

The proposed measure consists of several modifications to the existing mandatory requirement for demand control ventilation for high-density spaces. It applies to high-density spaces in most building types covered by Title 24, Part 6, such as offices, schools, universities, assembly spaces, churches, retail spaces, etc. Some spaces that were not previously covered by demand control ventilation (DCV), notably classrooms, would now be covered. The code change will modify the existing language in Section 120.1(c)3.

Occupant Sensor Ventilation Requirements (7 of 7)

The proposed measure is a modification of the existing mandatory occupant sensor ventilation control requirements in Title 24, Part 6. One of the main changes is that the existing requirements call for maintaining ¼ of the occupied minimum ventilation rate when the zone is unoccupied. The proposed requirement is to completely shut off ventilation if the space is unoccupied and the heating/cooling setpoints are satisfied. This change is facilitated by the fact that ANSI/ASHRAE Standard 62.1-2016 Ventilation for Acceptable Indoor Air Quality (ASHRAE 62.1) and the California Mechanical Code (CMC, Title 24, Part 4) now both allow “occupied standby mode” for selected spaces meaning that zero ventilation is allowed when the space is unoccupied. The proposed measure also modifies the zones to which occupant sensor ventilation control requirements apply.

Request for Feedback

The Statewide Utility Team encourages participation in the CASE Report development process through the submission of data—both primary sources and references to existing data. We are requesting data on areas such as energy savings, costs, market impacts, industry practices, barriers to code compliance, etc. from stakeholders. The data will inform the energy savings estimates, cost-effectiveness analysis, compliance and enforcement, and market impacts that will be presented in CASE Reports.

Do you have feedback or data to share? Send us an email at

California Statewide Utility Codes and Standards Program

This program is funded by California utility customers and administered by Pacific Gas and Electric Company, Southern California Edison, San Diego Gas and Electric Company, Southern California Gas Company, Sacramento Municipal District, and Los Angeles Department of Water and Power in preparation for the California Energy Commission’s Codes and Standards Buildings Advocacy.