Pick the path before you pick the sensors
On most commercial projects, the lighting controls conversation starts with hardware: which sensors, which dimming protocol, wired or wireless. The code conversation should come first, because it decides what the hardware has to do and what somebody will have to prove at the end.
Two documents set the baseline for most commercial work in the United States: ASHRAE/IES Standard 90.1 and the International Energy Conservation Code (IECC). The IECC’s commercial chapter lets a project comply either with its own provisions or with ASHRAE 90.1 as an alternative path, and the 2024 IECC references the 2022 edition of 90.1. Where the 2024 IECC is in force, a design team can often choose.
The decision that matters first: which compliance path your project follows, and what that means for the controls you specify and test. The answer is less about which code is easier and more about consistency. The project that gets into trouble is the one where the lighting designer worked from 90.1, the electrical engineer copied IECC exceptions from a previous job, and the person testing the system worked from neither.
One caution before going further. Adoption varies. Across Mississippi, Tennessee and Alabama, the edition in force depends on the state, sometimes on the city or county, and sometimes on who is paying for the building. Published sources even disagree about Mississippi’s status. We don’t assume. We confirm the edition with the authority having jurisdiction (AHJ) at the start of every project, and we’d encourage you to do the same. Our post on Mississippi’s commercial energy code goes into that question in more depth.
Where the two codes agree
Strip away the formatting, and 90.1-2022 and the 2024 IECC ask for the same families of controls:
- Local control. Occupants can operate the lighting in the space they are in, using a readily accessible manual control.
- Automatic shutoff. Lighting turns off when a space is empty, through occupancy or vacancy sensors in most enclosed spaces and through time-based scheduling where sensors don’t make sense.
- Light reduction. Occupants can lower the lighting in most spaces without turning it off. Bilevel switching or continuous dimming satisfies this.
- Daylight response. General lighting in daylight zones next to windows and under skylights responds to available daylight once the connected lighting in those zones passes a threshold.
- Exterior control. Exterior lighting turns off when daylight is available and is reduced late at night when the site is not in use.
- Functional testing. Installed controls are tested to show they work as the construction documents describe.
Both codes also cap lighting power, the watts per square foot you are allowed to install. Both include automatic receptacle control for certain space types, which surprises owners who think of the lighting section as “just the lights.”
The structure differs more than the intent. 90.1 organizes its interior control requirements around space types: you look up a conference room or a warehouse aisle and read what it needs. The IECC states its control requirements section by section, each with its own list of spaces and exceptions. Same destination, different map. The difference bites when a team switches paths halfway through design, or reuses a specification written for the other code.
According to ASHRAE’s fact sheet, DOE determined that 90.1-2022 saves roughly 10% over the 2019 edition. Lighting contributes through lower power allowances and tighter control language, but most of the controls content is a steady evolution rather than a rewrite.
What the 2024 IECC changed for lighting controls
The changes that matter most for controls, as summarized by LightNOW, are three:
- A lower wattage threshold for daylight-responsive controls. More daylight zones now need automatic daylight response. Small perimeter offices and short window bands that used to fall under the threshold may now be in scope.
- Functional testing for automatic receptacle controls. Installing the controlled outlets is no longer the end of it. Someone has to show that they actually turn off.
- Functional testing for high-end trim and demand-responsive controls, where installed. If the design caps light output with high-end trim, or sheds load on a utility signal, those functions get tested too.
We’d underline the third change. High-end trim and demand response are the features that disappear quietly. A technician trims a zone to 80%, an occupant complains, and the zone goes back to full output with no record. A demand response sequence is configured at startup and never triggered again. Testing those functions, and writing the result down, turns them from good intentions into verified behavior.
California’s Title 24 (2025 edition), effective January 1, 2026, goes further in places, including continuous dimming to 10% or lower and occupancy sensor delays of 20 minutes or less. It doesn’t apply in the Mid-South, but national retail and banking chains often carry Title 24 thinking into their prototype specifications, so it shows up on drawings for a new branch in Southaven or a store in Huntsville.
The checklist
Use this table as a coordination tool between the designer, the electrical contractor and whoever commissions the system. The requirement column is deliberately general. Thresholds, time delays, exceptions and space lists differ between the codes and between editions, so confirm the exact wording against the path your project follows.
| Control type | Typical requirement in both codes | Watch for | Functional test |
|---|---|---|---|
| Local manual control | A readily accessible manual control serving each space | Controls hidden in a closet or on a panel occupants can’t reach | Operate every control and confirm it serves the zone shown on the drawings |
| Occupancy or vacancy sensors | Automatic shutoff in listed enclosed spaces within a maximum delay; manual-on or partial-on in many spaces | Space lists and delays differ by path and edition | Leave the space, time the shutoff, confirm the partial-on level, and confirm vacancy-only spaces never switch on by themselves |
| Time-based shutoff | Scheduled off for lighting not covered by sensors, with a limited override | Holidays and second shifts missing from the schedule | Run the schedule, trigger an override, and confirm it times out |
| Light reduction | At least one intermediate level by bilevel switching or dimming | A “low” level that is barely lower than full | Step through each level and measure that it is a real reduction |
| Daylight-responsive controls | Automatic daylight response in sidelit and toplit zones above a wattage threshold | 2024 IECC lowers the threshold, so more zones qualify | Simulate high and low daylight at the sensor; confirm the zone dims and recovers without visible hunting |
| Automatic receptacle control | Controlled outlets in listed space types, off when unoccupied or after hours | 2024 IECC requires functional testing | Vacate the space or run the schedule; verify controlled outlets lose power |
| High-end trim | Where installed, maximum output set below full | 2024 IECC tests it where installed | Measure illuminance at the trimmed level; confirm the trim survives a power cycle |
| Demand-responsive controls | Where installed, reduce lighting load on a utility or grid signal | 2024 IECC tests it where installed | Send a test signal; confirm the designed reduction and the restore |
| Exterior lighting | Off in daylight; reduced during late-night hours | Photocells mounted where parking lot poles shade them | Cover the photocell or advance the clock; confirm off, on and reduced states |
| Documentation | Sequences in the construction documents; testing recorded | Test results that say “complete” with no values | A signed test log and configuration report delivered to the owner |
Where projects go wrong
The failures we see are rarely about the code text. They are about coordination.
- Mixing paths. A specification section written for an IECC project gets reused on a 90.1 project, or the reverse. Exceptions from one show up next to power allowances from the other, and nobody notices until plan review.
- Sensors that meet code on paper. A sensor drawn in the center of an office sits behind a bookcase after move-in. A warehouse sensor sees the top of the racking instead of the aisle. The drawings comply; the building doesn’t.
- Daylight zones left at factory settings. A bank branch with deep overhangs and tinted glass needs different calibration than a classroom with clerestories. The default setpoint is wrong in both.
- Receptacle control defeated at move-in. Furniture installers plug monitors into the uncontrolled half of the duplex. Now that the 2024 IECC requires testing, this becomes visible, which is a good thing.
- Testing by the installer, without a script. The person who programmed a system is the worst person to test it alone. They test what they remember setting, not what the drawings asked for.
What we’d do
If we were starting a new building or a major renovation in the Mid-South tomorrow, here is the order we’d follow.
- Confirm the edition and the path with the AHJ before schematic design, and record the answer in the project’s basis of design. If the jurisdiction allows both the IECC and 90.1, choose one and say so on the drawings.
- Write the sequence of operations by space type before choosing products. A conference room, an open office, a warehouse aisle and a parking deck each get a plain-language paragraph: what turns the lights on, what turns them off, what dims them, and what the occupant can override.
- Put functional testing in the specification, with a named responsible party, a test script per space type and a deliverable: a signed log plus a configuration report, in ANSI/NEMA C137.9 format where the platform supports it.
- Test high-end trim and demand response even when your path doesn’t strictly require it. They are the features most likely to be undone, and the cheapest to verify while the lift is still on site.
- Hand the owner the records, in a format the next technician can use without calling the installer.
Code compliance and commissioning are two halves of the same job. Our Energy Code Compliance service covers the first: path selection, control narratives, compliance documentation and plan review responses. Our multi-brand commissioning service covers the second, whatever manufacturer is in the ceiling. If you have an existing building and want to know how far it sits from either code, a Baseline Assessment includes a sample functional test of representative spaces and a straight answer about what it would take.
Filed under: ASHRAE 90.1-2022 · 2024 IECC · functional testing · daylight controls · energy code
