Meeting ASHRAE 90.1 and IECC Lighting Control Requirements with DALI-2 Systems

Energy codes have evolved from simple wattage limits to prescriptive requirements for how lighting must be controlled. Modern commercial building codes — including ASHRAE Standard 90.1 and the International Energy Conservation Code (IECC) — now mandate automatic shutoff, occupancy sensing, daylight harvesting, and individualized control in many space types. These requirements cannot be met with basic on/off switching or simple 0–10V zone dimming alone. They demand a control system that can address individual fixtures, respond to sensors, and report energy consumption. DALI-2 is well suited to this role, and understanding how its capabilities map to specific code requirements is essential for specifiers and contractors.

Occupancy sensing is one of the most widely mandated control functions. ASHRAE 90.1-2022 requires automatic lighting shutoff in virtually all enclosed spaces, and in open offices it requires that within 15 minutes of no occupancy being detected in a control zone, the controlled lights be turned off or uniformly reduced to 20 percent or less of full power. The 2024 IECC extends occupancy sensor requirements to additional space types, including data centers, laundry rooms, and healthcare facilities. A DALI-2 system implements this by connecting occupancy sensors — which are standardized as input devices under IEC 62386-301 — directly to the bus. When a sensor reports that a zone is vacant, the application controller sends a fade command to the relevant group of drivers, dimming or switching off the lights without any manual intervention.

Daylight-responsive control, or daylight harvesting, is required in spaces with significant access to natural light. Both ASHRAE 90.1 and the IECC require daylight controls in primary sidelit areas — the floor area adjacent to vertical windows, extending roughly one window-head-height into the space — and in toplit areas under skylights, when the total general lighting wattage in that zone reaches 75 W or more. The control must be capable of continuously dimming the electric lights in response to available daylight, reducing power to less than 35 percent of design power when sufficient daylight is present. A DALI-2 photosensor, also an IEC 62386-301 input device, measures illuminance at the work plane and sends the data to the application controller, which adjusts the output of individual drivers or groups to maintain a target illuminance setpoint. Because DALI-2 supports individual addressing, the daylight zone can be precisely defined without re-wiring — a significant advantage over 0–10V systems, where zoning is hardwired and changes require physical rewiring.

Individual occupant control is another growing requirement. ASHRAE 90.1-2022 requires that in open offices, each occupant have the ability to control the lighting in their immediate workspace, either through a personal control device or through a software interface. DALI-2 makes this straightforward: each workstation's overhead fixture can be assigned to a group corresponding to that workstation, and the occupant can adjust brightness via a wall controller, a desktop device, or a smartphone app connected through the DALI-2 gateway. The 20 percent rule in ASHRAE 90.1-2022 — which allows unoccupied zones to remain lit at no more than 20 percent power when an adjacent zone is occupied — is also easily implemented, because the application controller can independently manage the brightness of each group based on occupancy status.

Energy metering and reporting is a less commonly discussed but increasingly important code requirement. Many jurisdictions now require submetering of lighting systems in commercial buildings above a certain size, and green building certification programs such as LEED and BREEAM award points for energy monitoring. DALI-2 drivers can report their actual power consumption on command, and the application controller can aggregate this data across the system and expose it via BACnet, Modbus, or a REST API to a building management system or energy dashboard. This eliminates the need for separate current transformers and metering hardware on each lighting circuit, reducing both cost and installation complexity.

The flexibility of DALI-2 addressing also simplifies compliance with control zoning requirements. Both ASHRAE 90.1 and the IECC define maximum control zone sizes based on space type and daylight access. In a 0–10V system, each zone requires a separate control wire pair, so adding or reconfiguring zones means pulling new cable. In a DALI-2 system, all fixtures share the same two-wire bus, and zones are defined in software by assigning drivers to groups. A single bus can support up to 16 groups, and a driver can belong to multiple groups simultaneously, so the same fixture can participate in an occupancy group, a daylight group, and a scene group without any wiring changes. This software-defined zoning makes it far easier to meet code-required zone sizes and to adapt the system if the space layout changes after installation.

It is worth noting that code compliance depends on the entire system, not just the driver. A DALI-2-certified driver connected to a non-certified sensor or a controller that does not implement the required automatic shutoff timing will not produce a compliant installation. Specifiers should ensure that the application controller supports the specific code-mandated sequences of operation — including the required time delays, the minimum dim levels, and the daylight control logic — and that all bus devices are DALI-2 certified. Many controller manufacturers provide pre-built code-compliant application templates that can be loaded during commissioning, which reduces the risk of configuration errors.

For a constant-voltage DALI-2 driver deployed in a commercial office, retail, or hospitality project, the value proposition is clear: it provides the individual addressability, sensor integration, dimming precision, and energy reporting needed to satisfy modern energy codes, while the constant-voltage output supports the LED strips and linear fixtures that dominate contemporary architectural lighting. As energy codes continue to tighten — with each new edition of ASHRAE 90.1 and the IECC adding more stringent control requirements — the ability to update control sequences via software rather than hardware becomes an increasingly valuable feature of a DALI-2 installation.