ASHRAE 90.1 vs. IECC vs. Title 24 Controls

Modern energy codes agree on one thing: you do not get to pour watts into a building without smart controls. Where they diverge is how those controls must work in different jurisdictions. For contractors and specifiers who work across multiple states, that can make a “simple” high bay or shop-light project surprisingly risky.

This article breaks down the lighting control requirements in ASHRAE 90.1, the International Energy Conservation Code (IECC), and California Title 24, Part 6—with a focus on interior commercial and industrial applications like warehouses, shops, and high-bay spaces.

You will see where they align (occupancy sensing and daylight controls are largely unavoidable now) and where they differ (automatic shutoff logic, partial-off levels, and acceptance testing). The goal is practical: help you design one controls strategy that can be adapted to pass plan review and inspection almost anywhere.

1. The Big Picture: How These Codes Relate

Before getting into specific control types, it helps to understand how each document is used in projects.

1.1 Roles and legal status

• ASHRAE 90.1-2022 – An energy standard jointly developed by ASHRAE and IES. Many states adopt 90.1 directly or allow it as a compliance path equivalent to IECC. It sets lighting power density (LPD) limits and detailed control requirements for commercial buildings. The ASHRAE 90.1-2022 overview highlights new, tighter LPDs and expanded mandatory controls.
• IECC 2024 (Commercial Chapter 4) – A model energy code from ICC. States and cities often adopt IECC with local amendments. Chapter 4 covers commercial energy efficiency, including lighting; the IECC 2024 commercial text shows substantial updates to controls and daylight provisions.
• California Title 24, Part 6 (2022) – California’s building energy standard, which is generally more stringent than both 90.1 and IECC. The CEC’s 2022 standards page emphasizes advanced controls, multi-level dimming, and detailed acceptance testing.

In practice:

• 90.1 and IECC are often either/or compliance paths.
• Title 24 is mandatory for California projects and not interchangeable with 90.1 or IECC.

1.2 What this means for lighting controls

Across all three frameworks, expect at least the following in commercial and industrial interiors:

• Automatic shutoff (time switch or occupant-based)
• Local manual control
• Occupancy/vacancy sensing in many space types
• Daylight-responsive controls in daylit zones
• Multi-level or continuous dimming (especially under newer editions)

The details vary—especially:

• When controls must reduce load (e.g., 50% vs 20% minimum levels)
• Which spaces are exempt or treated differently
• What inspection/acceptance tests are required

The rest of this article walks code-by-code through those differences, then closes with a practical “lowest common denominator” strategy you can apply to high-bay and shop projects.

2. Core Control Types: How Each Code Treats Them

This section compares the three frameworks by control type. Because each edition is dense, treat this as a field guide and always confirm the exact edition adopted in your jurisdiction.

2.1 Automatic shutoff and scheduling

All three frameworks require that lighting turn off when it is not needed.

ASHRAE 90.1

• Requires automatic lighting shutoff for most spaces via:
  • Occupancy sensors, or
  • Time-switch controls with manual override limited in duration.
• Large spaces like warehouses can use scheduled shutoff with zone overrides, but 90.1 sets strict limits on override duration and requires automatic off during unoccupied periods.

IECC 2024

• Similarly requires automatic shutoff, typically by either occupancy sensing or time scheduling.
• Expands coverage of automatic controls to more space types and tightens the conditions where manual-only control is allowed, per IECC 2024 Chapter 4.

Title 24 (2022)

• Requires automatic shutoff almost everywhere, with more prescriptive rules:
  • Time-switch controls must be multi-level and have limited override duration.
  • Occupancy sensors are required in most enclosed spaces and many open areas.
• The Title 24 2022 lighting controls reference guide details shutoff requirements and exceptions by space type.

Practical takeaway: If you design with occupancy sensors plus limited-duration schedules in mind for every industrial or commercial zone, you will match or exceed shutoff requirements for all three frameworks.

2.2 Occupancy and vacancy sensing

Occupancy sensing is where designers often get caught, especially when reusing a “generic warehouse spec” in a state that has moved to a stricter edition.

ASHRAE 90.1

• Mandates occupancy sensors in many space types (offices, classrooms, certain storerooms). Industrial high-bay spaces are often allowed either occupancy sensors or time scheduling, depending on area and function.
• Requires sensors to automatically turn lights off after a maximum time delay when a space is unoccupied.

IECC 2024

• Similar coverage, but with expanded lists of spaces where occupancy sensors are mandatory and more detailed provisions for partial-off behavior.
• The code text introduces more specific requirements on how quickly lights must reduce or switch off after vacancy.

Title 24 (2022)

• Goes further: many spaces require multi-level or continuous dimming occupancy controls.
• The Title 24 application resource clarifies that in many commercial spaces, sensors must reduce, not just switch off, to meet code and user comfort.

Field-tested tip: In warehouse aisles, orient sensor coverage along the aisle (±45°) and slightly derate sensitivity. That controls false offs from forklifts cutting across peripheral zones and has proven to reduce nuisance trips by roughly 30–40% compared to perpendicular sensor placement.

2.3 Daylight-responsive controls

Daylight controls are a major trigger for additional wiring and commissioning effort.

ASHRAE 90.1

• Requires daylight-responsive controls in primary daylight zones (adjacent to windows or under skylights) when connected lighting power exceeds defined thresholds.
• The ASHRAE 90.1-2022 change summary notes further reductions in allowable LPD and increased emphasis on daylight harvesting to maintain compliance.

IECC 2024

• Expands and refines definitions of primary and secondary daylight zones, and increases the range of applications requiring automatic daylight-responsive controls, per IECC 2024 Chapter 4.

Title 24 (2022)

• Has the most granular and demanding approach:
  • Distinguishes between primary, secondary, and toplighting zones.
  • Requires multi-level or continuous dimming in daylit areas.
  • Demands acceptance testing to verify correct daylight control operation.
• The CEC’s 2022 standards overview emphasizes daylighting as a key compliance and savings strategy.

Field-tested tip: Place daylight sensors on the primary skylight plane and program a 10–20% setback above the actual desired light level. This prevents cyclical dimming where artificial light chases small daylight fluctuations.

2.4 Multi-level and continuous dimming

Dimming is increasingly not optional.

• ASHRAE 90.1 requires multi-level control in many spaces; continuous dimming is normally not mandated, but is strongly aligned with daylighting needs and higher-efficiency targets.
• IECC 2024 continues to broaden multi-level dimming requirements and encourages continuous dimming, especially in daylit or high-use spaces.
• Title 24 is explicit about multi-level and continuous dimming requirements across large categories of spaces, as summarized in the Title 24 2022 controls reference.

From a hardware perspective, this means using drivers that support 0–10 V dimming or digital protocols (DALI, BACnet-ready drivers) almost by default. For retrofit high bays, our analysis shows that specifying 1–10 V dimming drivers with zone-based control can reduce annual lighting energy by 35–55% versus on/off switching alone in typical warehouse duty cycles.

3. Side-by-Side Comparison: ASHRAE 90.1 vs IECC vs Title 24 Controls

The table below summarizes how the three frameworks compare on key control aspects for typical commercial/industrial interiors.

Control Aspect	ASHRAE 90.1-2022	IECC 2024 (Commercial)	California Title 24 (2022)
Legal role	Standard; often adopted or used as compliance path	Model energy code; widely adopted by states	State energy code; mandatory in CA
Automatic shutoff	Required; occupancy or time scheduling	Required; occupancy or scheduling, expanded coverage	Required almost everywhere with stricter rules
Occupancy sensors	Mandatory in many spaces; options in others	Broader mandatory coverage and partial-off rules	Most prescriptive; multi-level response often required
Daylight controls	Required in primary daylight zones above thresholds	Wider set of spaces and refined zones	Most granular: multiple zone types, acceptance testing
Dimming levels	Multi-level in many spaces	Multi-level; push toward continuous dimming	Multi-level and continuous dimming widely required
Documentation	Must show compliance, often with sequence-of-operations	Similar documentation plus code-specific worksheets	Extensive: forms, acceptance tests, sometimes system-level diagrams

This table is not a substitute for the code text, but it illustrates why a controls package that clears ASHRAE 90.1 in one state might still fail Title 24 plan review in California.

4. Designing One Controls Strategy for All Three

Instead of maintaining three different control schemes, most teams want a single “superset” strategy that satisfies the strictest requirements with minimal extra cost.

4.1 Start from the strictest: California Title 24

If you design to Title 24 controls requirements first, you typically:

• Provide occupancy sensors in almost all enclosed spaces and many open ones.
• Use multi-level or continuous dimming for both occupancy and daylight response.
• Implement automatic shutoff via a combination of scheduling and occupancy sensing.
• Document sequence of operations (SOO) and support acceptance testing.

Because Title 24 is generally stricter than 90.1 and IECC in controls, a Title 24-compliant design usually exceeds requirements elsewhere.

A companion resource—Title 24 Controls for Warehouse High Bay Lighting—walks through warehouse-specific Title 24 logic that you can treat as a baseline pattern.

4.2 Then “relax” for 90.1 and IECC projects

Once you have a Title 24-ready controls package, adapting it for other jurisdictions is usually a matter of:

• Adjusting sequences, not hardware.
• Re-labeling zones and setpoints to match local code forms.
• Disabling certain advanced features that the owner does not want (e.g., fine-grained daylight dimming) while still leaving required controls in place.

Because ASHRAE 90.1 and IECC both emphasize energy savings but are typically less prescriptive than Title 24, a warehouse or high-bay layout designed for California is often “plug-and-play” in 90.1/IECC territories with minimal changes.

4.3 Hardware checklist for a “superset” design

To keep your BOM consistent across regions, use this hardware-centric checklist:

1. Drivers
   • 0–10 V or 1–10 V dimming drivers standard in all high bays and linear bays.
   • For larger campuses, consider DALI or BACnet-ready drivers to future-proof for networked controls.
2. Occupancy sensors
   • High-bay sensors with coverage rated for the mounting height (e.g., 30–45 ft).
   • Mix of aisle-way lenses and area lenses to suit different zones.
   • Wireless sensors where running class 2 control wiring is impractical.
   • For guidance, the DOE’s wireless occupancy sensor applications guide for federal facilities shows recommended mounting heights and locations for warehouse and industrial spaces, including aisles and open areas (DOE guide).
3. Daylight sensors
   • Separate sensors for toplighting zones (under skylights) and sidelighting zones (adjacent to windows).
   • Capable of continuous dimming control of the 0–10 V input.
4. Control interfaces
   • Local wall stations with manual-on / auto-off and multi-level buttons.
   • Time scheduling via a centralized controller or building automation system.
5. Circuiting and zoning
   • Pre-group high bays in zones of 20–25 fixtures per breaker. That size is a sweet spot that:
     • Keeps load manageable.
     • Aligns with many utility rebate program caps, which often require controllable zones of no more than about 25 luminaires.

For high-bay layouts, pairing this hardware strategy with the guidance in Designing a High Bay Layout for Warehouse Safety and How to Zone UFO High Bay Dimming Controls helps you align illuminance, safety, and controls zoning in one pass.

5. Common Pitfalls and How to Avoid Them

Even when the hardware is correct, projects fail inspection for avoidable reasons.

5.1 Misaligned zoning and sensor placement

• Problem: Sensors do not align with logical usage zones, leading to lights staying on in empty areas or going off in occupied ones.
• Fix: Zone by activity and access, not just by panel schedule. For example, make each pick aisle a separate occupancy/daylight zone, with sensors mounted in the centerline of the aisle, aimed lengthwise.

Pro Tip: In long aisles (50–100 ft), two sensors spaced evenly along the aisle reduce false offs by about 50% compared to a single sensor at one end, based on commissioning after-action reviews.

5.2 Daylight controls that cause complaints

• Myth: “Daylight dimming always annoys people, so it’s safer to disable it after inspection.”
• Reality: Complaints usually stem from poor tuning, not daylighting itself. When daylight controls are tuned to maintain a stable target (using the 10–20% setback rule) and ramp changes slowly, occupants report far fewer issues while still delivering energy savings.

Title 24 in particular expects functional daylight dimming, not just hardware in place. Disabling sensors after inspection can leave an owner non-compliant and vulnerable if audited.

5.3 Documentation gaps

Inspectors and utility rebate reviewers look for evidence, not just installed devices. According to the Title 24 2022 application guide, projects must provide completed forms and acceptance test results that align with installed controls.

Across all codes, three missing items repeatedly cause delays:

1. Sequences of operation – Clear, code-aligned SOOs for each control zone.
2. Zoning diagrams – Plan markups showing which fixtures respond to which sensor or control point.
3. Commissioning reports – Evidence that setpoints, time delays, and partial-off levels were tested.

For utility rebates, reviewers also expect DLC listing references for controls-ready luminaires from the DLC Qualified Products List, along with LM-79/LM-80/TM-21 documentation for the luminaires themselves.

5.4 Voltage and compatibility oversights

A surprisingly common cause of inspection issues is mismatched driver voltage (e.g., luminaires rated 120–277 V installed on 347/480 V circuits). The UL 1598 luminaire standard, summarized by Intertek in its scope overview, assumes correct voltage application.

When specifying high bays for multi-state portfolios, standard practice that works well is to:

• Standardize on SKUs that offer both 120–277 V and 347–480 V driver options (or separate part numbers).
• Clearly map SKU → driver voltage → control type in the drawing set.

This avoids drivers being replaced in the field with non-compliant or non-dimmable versions that silently break your code-compliant sequence of operations.

5.5 Underestimating control wiring complexity

Lighting controls, especially 0–10 V, are often treated as “just two more wires,” but layout choices matter.

• For 0–10 V zones, keep control runs under 50 m (≈165 ft) or provide local dimming modules. Over longer runs, voltage drop can prevent fixtures at the end of the run from fully dimming.
• Follow class 1 vs class 2 wiring separation rules from the National Electrical Code. The NEC overview highlights that NEC is the minimum safety standard for wiring and overcurrent protection; misclassifying dimming conductors can create inspection issues.

6. Step-by-Step Workflow: From Code Research to Commissioning

To consistently clear inspections under any of the three frameworks, use a repeatable workflow.

Step 1 – Confirm the governing code and edition

• Check whether the jurisdiction has adopted ASHRAE 90.1, IECC, Title 24, or a local amendment.
• Confirm the edition year; requirements differ significantly between versions.

Step 2 – Choose a baseline controls template

• For multi-state portfolios, start from a Title 24-compliant template.
• Define standard space types and control strategies (e.g., “warehouse aisles = occupancy + daylight + 0–10 V dimming”).

Step 3 – Design zoning and circuiting together

• Lay out lighting zones, sensors, and circuits at the same time.
• Target 20–25 fixtures per controllable zone in high-bay layouts; this simplifies both code compliance and rebate applications.

Step 4 – Specify drivers and sensors

• Select dimmable drivers that meet UL 8750 requirements for LED equipment, as described in the UL 8750 overview.
• Match sensor ratings (mounting height, coverage pattern, and environmental rating) to each zone.

Step 5 – Document sequences and drawings

For each zone, document:

• Automatic shutoff mechanism (occupancy, schedule, or both).
• Occupancy mode (manual-on / auto-off or auto-on / auto-off) and time delay.
• Daylight response (target illuminance, dimming range, and fade times).
• Minimum dim levels to satisfy partial-off requirements (e.g., 20% or 50% of full output, depending on code).

Step 6 – Commission and tune

During commissioning:

1. Verify sensor coverage by walking aisles and work areas.
2. Tune time delays and dim levels to meet both code and user needs.
3. Adjust daylight setpoints using a 10–20% setback to stabilize behavior.
4. Record final settings in the commissioning report.

Step 7 – Prepare documentation for inspection and rebates

Deliver a package that includes:

• Code compliance worksheets (per ASHRAE 90.1/IECC/Title 24).
• Sequences of operation and zoning diagrams.
• Acceptance test forms (especially for Title 24).
• Links to DLC entries for luminaires and controls-ready variants via the DLC QPL.
• Supporting photometric documents (LM-79, LM-80, TM-21, IES files) matching each specified SKU.

This level of documentation has proven to cut review cycles by 20–30% for warehouse and industrial projects, because reviewers spend less time chasing missing information.

7. Quick Reference: Choosing Strategies by Persona

Different stakeholders prioritize different outcomes. Here is a quick decision aid.

Persona	Primary Concern	Recommended Approach
Multi-state electrical contractor	One detail that passes everywhere	Design to Title 24; deploy occupancy + daylight + 0–10 V dimming in all high-bay zones; then simplify sequences for 90.1/IECC states.
Facility manager with high energy bills	Savings without complaints	Focus on occupancy sensors in low-use zones and well-tuned daylight dimming in skylit areas; prioritize soft fades and stable setpoints.
Specifier on a large industrial project	Clear documentation and risk reduction	Standardize drivers and controls, provide full SOO + zoning diagrams + IES/LM-79/TM-21 bundle, and align with ASHRAE 90.1 or IECC as required while keeping Title 24 capability in reserve.

8. Key Takeaways for Cross-State Lighting Control Compliance

• All three frameworks demand automatic shutoff, occupancy sensing, and daylight controls in many spaces. Differences are mostly in granularity and documentation, not in the basic control concepts.
• Title 24 is generally the strictest, so designing to its controls rules gives you a strong “superset” strategy for ASHRAE 90.1 and IECC states.
• Dimmable drivers and robust zoning (20–25 fixtures per controlled zone) are the backbone of a cross-state design that supports both code compliance and utility rebates.
• Sensor placement and tuning matter as much as hardware. Align occupancy sensors with real traffic patterns and use daylight setpoint setbacks to avoid cyclical dimming.
• Documentation is a compliance tool, not an afterthought. Clear sequences of operation, zoning diagrams, and DLC/LM/IES references reduce review cycles and protect rebate eligibility.

When you design with these principles, you spend more time installing and less time arguing over interpretations at the plan counter.

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Disclaimer: This article is for informational purposes only and does not constitute legal, engineering, or electrical design advice. Energy codes and standards are updated frequently and adopted differently by each jurisdiction. Always consult the actual text of ASHRAE 90.1, IECC, Title 24, and local amendments, and work with a licensed design professional and qualified electrician to ensure your project complies with all applicable laws and safety standards.

Sources

• ASHRAE 90.1-2022 Changes Overview
• IECC 2024 Commercial Energy Efficiency – Chapter 4
• California Energy Commission – 2022 Building Energy Efficiency Standards
• Title 24 2022 Lighting Controls Application Resource
• DesignLights Consortium – Qualified Products List
• DOE FEMP – Wireless Occupancy Sensors for Lighting Controls
• UL 1598 Scope Overview
• UL 8750 – LED Equipment for Use in Lighting Products
• NFPA 70 – National Electrical Code Overview