Nonresidential HVAC Controls

Measure Description

This CASE Report consists of three submeasures: adding prescriptive requirements for dedicated outside air systems (DOAS), and modifying existing prescriptive requirements for VAV zone controls, and expanding prescriptive requirements for air side economizer and integrated economizer operation.  Further details can be found below. 

Expand Economizer Requirements

This submeasure aims to modify  both  economizer requirements and integrated economizer requirements. The measure will expand economizer requirements to include smaller-sized units and expand integrated economizer requirements by requiring lower compressor turndown. This submeasure was previously referred to as an “Air efficiency” measure. 

VAV Deadband Airflow

 This measure would adjust prescriptive requirements for variable air volume (VAV) zone controls. Currently, when a zone is in the deadband operation, flow controls must meet mandatory requirements of Section 120.1 for ventilation requirements and an additional prescriptive requirements of fixed minimum rate flow rate of 20% from section 140.4(d). This measure would remove the 20 percent prescriptive requirement, allowing for lower airflow during deadband operation, while ensuring indoor air quality. The measure is based on research conducted for ASHRAE Research Project (RP)-1515, which was co-funded by the California Energy Commission PIER program and evaluated occupants’ thermal comfort and air quality satisfaction of reduced airflows using lab and field studies. Findings from RP-1515 resulted in the approval of Addendum AU to ASHRAE 90.1-2016, which reduced minimum airflow requirements. As a result, this measure proposes to align Title 24, Part 6 with ASHRAE Standard 90.1-2019 and simplify the existing code requirements.  

Dedicated Outside Air Systems (DOAS)

This measure will add prescriptive requirements to dedicated outdoor air system units (DOASu) when used as the primary source of ventilation in nonresidential buildings to include a minimum level of efficiency criteria and an exception to economizing for space conditioning when combined with ventilation heat recovery. The combination of a separate DOAS unit and heating and cooling system as a package is referred to as a Dedicated Outdoor Air System (DOAS).  

This measure is based on research into low energy HVAC systems used in California nonresidential net zero energy buildings, field monitoring research conducted by PG&E’s Code Readiness project, and code change enhancements made in Washington State Building Energy Code, starting in 2015 and up to changes adopted in 2019. This strategy has been shown to cost effective to operate while reducing source energy by 30% compared with standard designs.  

The measure will add a prescriptive option to install a DOAS with a minimum set of efficiency criteria. This includes: 

• A minimum level of sensible energy recovery ratio with bypass capabilities. 
• Ability to modulate fan speed of the DOAS unit. 
• A total system fan power limit on DOAS units, including <5hp 
• Compliance with DCV and Occupancy Standby. 
• Zone terminal fans for cooling or heating cycle to off if no call for conditioning. 
• DX-DOAS or DOAS with active cooling must have a maximum reheat limit of 60F when in cooling model. 

DOAS units with a minimum level of ventilation heat recovery and free cooling controls would be required to achieve the exception to economizing.  

Exhaust Air Heat Recovery

This measure will add prescriptive requirements to all nonresidential systems for exhaust air heat recovery depending on climate zone, hours of operation, and fraction of outside air. 

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.

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