Measure Overview
This measure proposes the following revisions to the required controls for space-conditioning systems (Section 120.2). The proposed changes include updates to the requirements and adding definitions for clarity.
- Define terms for fault detection and diagnostics (FDD)
- Require the installation of an FDD system for new nonresidential buildings and alterations over 100,000 square feet, with heating or cooling capacities over 300,000 Btu/hr
- Require baseline functionality, communication, and accessibility
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This measure page will be updated as the 2028 code cycle progresses. For questions or suggestions, email [email protected]. Please include the measure name in the subject line.
Scope of Proposed Code Change
| Building Type(s) | Construction Type(s) | Type of Change | Updates to Compliance Software | Third Party Verification |
| Nonresidential | New construction, alterations | Mandatory | No updates | No changes to third party verification |
Justification for Proposed Change
HVAC fault detection and diagnostics (FDD) provides building operators with a proactive way to maintain and optimize their systems by bringing operational data together and providing actionable insights for inefficient operation. FDD can sustain other HVAC efficiency measures by monitoring their performance and identifying repairs. FDD enables a resilient energy efficiency strategy for buildings.
HVAC systems are designed, built, and operated to meet conditioning and ventilation needs of the building, ideally using as little energy as possible to do it. Modern HVAC direct digital control (DDC) systems provide the access to understanding HVAC system operation and automatically controlling the system, while also providing ability to monitor, trend, and analyze the system. However, over time HVAC systems lose their efficiency due to installation error, wear-and-tear on system components, lack of maintenance, and changes in control strategies.
Already-established processes such as start-up commissioning and existing building commissioning attempts to verify proper operation and/or optimize these systems. FDD is an automated version commissioning, using rule- or model-based approaches to identify faults that raise energy usage and limit the functionality of the system. The FDD system will also identify possible repairs to bring the system back to its original efficient operations or optimize it to save more energy than before.
Relevant Documents
Round One Utility-Sponsored Stakeholder Meeting Materials
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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.