Nonresidential HVAC Controls

Measure Description

This CASE Report will further expand on economizer requirements as one submeasure and will include two additional HVAC submeasures related to HVAC controls. In total, this CASE Report will include three submeasures as described below.

Updated Economizer Requirements

During the 2019 code cycle, water-side economizer requirements were expanded to include some radiant and chilled beams systems that were previously exempted. This submeasure aims to expand on this foundational work, including further expanding the economizer requirement to cover large variable refrigerant volume (VRV) systems and heat pump systems with significant interior zones or internal loads. Unique code changes presented in this submeasure are presented below.

• Lowering the cooling capacity that ‘triggers’ the economizer requirement in code.
• Increasing the stringency/efficiency of packaged unit compressor turndown to allow packaged units to have fully-integrated economizers.
• Improving economizer design requirements for systems housing economizers to lessen negative impacts on indoor air quality.
• Enacting minimum clearances from intake/exhaust openings to the roof screens, which block the HVAC equipment from site to prevent the entrapment of exhaust.
• Requiring powered-modulated relief for packaged HVAC units with economizers to ensure that excess outdoor air introduced into the system is released.

Guest Room Controls

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

Variable Air Volume (VAV) Minimum Airflow

This submeasure would allow terminal box minimum airflow requirements to be based on outdoor flow rate as opposed to a fixed minimum.

Dedicated Outside Air Systems (DOAS)

This measure will add prescriptive requirements to Dedicated Outside Air Systems (DOAS) when used as the primary source of ventilation in nonresidential buildings to include a minimum level of efficiency criteria and control capabilities. This measure is based on research conducted by PG&E’s Code Readiness project and code enhancements in Washington State Building Energy Code on DOAS in 2015 and 2017.  

The measure will also add prescriptive requirements for exhaust air heat recovery previously presented in draft language from 2019 Title 24, Part 6 and similar to the requirements in the current version of ASHRAE 90.1.