Nonresidential HVAC Controls

Measure Description

VAV Deadband Airflow

This measure would amend the existing prescriptive requirement for zone airflow rates in Section 140.4(d) by specifying that the primary airflow in the deadband to be the design ventilation airflow, which would align with recent changes to ASHRAE Standard 90.1 (2019). This measure would impact both new and existing buildings which utilize variable air volume HVAC systems.

Expand Economizer Requirements

This measure would incorporate two changes to the existing prescriptive requirements for economizers in Section 140.4 (e). This would impact new construction as well as major alterations and additions when a new HVAC unit is installed. These requirements would include the following:

1. Reduce economizing threshold from current level of 54,000 Btu/h to 33,000 Btu/h
2. Modify wording within Table 140.4-D to align with proposed changes in ASHRAE 90.1
3. Incorporate an exception to exempt systems from economizer requirements if an area meets the new dedicated outside air system prescriptive requirements.

Dedicated Outdoor Air Systems (DOAS)

This measure would add prescriptive requirements to DOAS when used as the primary source of ventilation in nonresidential buildings to include a minimum level of efficiency criteria and control capabilities and an exception to economizing. This would impact primarily new construction though would also cover all major alterations and additions when a new HVAC system was installed of this type in existing buildings.

A DOAS in this context is defined as a HVAC system which delivers 100 percent ventilation air separately from any heating and cooling system.

This would apply to all DOAS being used as a buildings primary means of ventilation of any size in a nonresidential application. The efficiency criteria include:

1. Providing each space with either:
   1. A separate cooling system with an economizer or
   2. A DOAS unit with minimum level of sensible energy recovery ratio, demand control ventilation when above 1,000 cfm, and with bypass capabilities for ventilation economizing.
2. DOAS unit fan systems shall have the ability to modulate fan speed, primarily for balancing and reducing operation fan power.
3. Zone terminal fans for cooling or heating must cycle to off if no call for conditioning.
4. Ventilation supply air shall be delivered directly to a space or downstream of a terminal unit cooling or heating coil.
5. DX-DOAS or DOAS with active cooling must have a maximum reheat limit of 60F when in cooling mode.
6. A total system fan power in line with prescriptive fan power tables in 140.4 (c).

Exhaust Air Heat Recovery

This measure would add new prescriptive requirements for exhaust air heat recovery requirements in California. The requirements are based on similar requirements from ASHRAE Standard 90.1 which take into account climate zone, design airflow rate, percent of outdoor air, and hours of operation but are modified for California’s 16 climate zones and utilize a sensible recovery ratio rather than an enthalpy recovery ratio as the performance metric needed for devices. The proposal also adopts several related exemptions from the ASHRAE Standard 90.1 on exhaust air energy recovery, Section 6.5.6.1.

Submeasures Moved to Future Code Cycles

The Statewide CASE Team is no longer pursuing the proposed changes listed below as it was determined that they did not meet the Energy Commission’s requirements for market readiness, technical feasibility, cost-effectiveness, or enforceability at the time they were considered.

Guest Room Controls

This measure proposes to require ventilation to be shut off to the guest room within 5 minutes of all occupants leaving the room, and require temperature setpoints of at least 60°F for heating and 80°F for cooling for unrented and unoccupied guest rooms. These requirements would align Title 24 Part 6 with the guest room ventilation control requirements in ASHRAE Standard 90.1 (2016) and guestroom purge requirements of 189.1 (2017).

To support ongoing research and future code cycle consideration, additional information on nonresidential thermal bridging can be submitted to the Statewide CASE Team through info@title24stakeholders.com. Materials that the Statewide CASE Team developed when investigating this code change for the 2022 code cycle will be moved to the Future Code Cycles section of this website. Follow this link to find materials on guest room controls.

Relevant Documents

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

CASE Reports

• CASE Study Results Report – Nonresidential HVAC Controls
• Final CASE Report – Nonresidential HVAC Controls
• Addendum to Final CASE Report – Nonresidential HVAC Controls (Updated March, 2021)
• Draft CASE Report – Nonresidential HVAC Controls

Round Two Utility-Sponsored Stakeholder Meeting Materials

• Nonresidential HVAC Controls Submeasure Summary (Updated 4/10/2020)
• Presentation – April 14 – Nonresidential and Single Family Part 2
• Notes – April 14 – Nonresidential and Single Family Part 2

Round One Utility-Sponsored Stakeholder Meeting Materials

Submeasure Summaries

• Nonresidential HVAC Controls Submeasure Summary (Updated 4/10/2020)
• Updated Economizer Requirements Submeasure Summary 9-27-2019
• Nonresidential HVAC VAV Minimum Airflow Submeasure Summary 9-6-2019
• Nonresidential HVAC Dedicated Outside Air Systems Submeasure Summary 9-12-2019

Utility-Sponsored Stakeholder Meeting Presentations

• Presentation – Oct. 15 – Nonresidential HVAC Part 1 Utility-Sponsored Stakeholder Meeting
• Presentation – Nov 5th – Nonresidential HVAC and Envelope Part 2 Utility-Sponsored Stakeholder Meeting

Utility-Sponsored Stakeholder Meeting Notes

• Notes – Oct. 15 – Nonresidential HVAC Part 1 Utility-Sponsored Stakeholder Meeting
• Notes – Nov 5th – Nonresidential HVAC and Envelope Part 2