Commercial building energy codes impose design standards for nonresidential buildings’ energy efficiency. Many states have implemented an energy code to regulate building design.
For lighting, the regulations combine prescriptive and mandatory requirements. Primary prescriptive requirements include maximum lighting power allowances by building or space type. Primary mandatory requirements cover a wide range of lighting controls. There may also be administrative and testing requirements, such as functionally testing lighting controls and turning over documentation to the owner.
Today, a majority of energy codes are based on the following:
- ASHRAE/IES Standard 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings, published by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) and the Illuminating Engineering Society (IES). It is updated every three years.
- The International Energy Conservation Code (IECC), published by the International Code Council. It is also updated every three years. The IECC references 90.1 as an alternative standard, so designers have a choice.
To be clear, 90.1 and the IECC are not codes. Instead, they provide code-ready language that jurisdictions can use to implement commercial building energy codes. Some states, such as California, adopt unique codes.
For instance, in buildings that comply with a majority of energy codes, lighting controls must turn off or reduce lighting when not in use. These requirements have become more detailed as codes evolved.
This article pores through 90.1 and the IECC to summarize these requirements.
New national reference standard
On Sept. 26, 2014, the U.S. Department of Energy (DOE) named the ASHRAE/IES 90.1 2013 energy standard as the new national energy reference standard, superseding the 2010 version. This mandate requires all states to adopt an energy code at least as stringent as 90.1 2013 by October 2016 or justify noncompliance. Traditionally, 37 states have complied with these mandates, though that number dropped to less than one-half of states for the earlier ruling recognizing 90.1 2010.
The 2013 version of 90.1 adjusted maximum allowable lighting power allowances, with some up and some down. The biggest changes to the standard imposed more detailed lighting control requirements and a new tabular format for implementing lighting power allowances and controls by building or space type. The tabular format was developed to simplify application; the designer looks up a space type and sees at a glance the requirements for that space. However, the control requirements in the earlier text may appear confusing until one realizes they are all directly connected to these tables.
For the space-by-space method, there are two tables: one lists space types found in multiple building types, and the other lists spaces generally found in one building type. The standard contains language applicable to these tables that must be referenced separately.
For example, if using the space-by-space method in open offices, a lighting power density (LPD) limit of 0.98 is prescribed. The room cavity ratio (RCR) threshold is 4, which means an additional lighting power allowance of 20 percent can be used if the actual RCR (2.5 × room cavity height × room perimeter length ÷ room area) is greater than the threshold. Choices of controls are then listed.
In open offices, space controls are required for users, and all lighting must be capable of reduction. If daylight is available, daylight area lighting must be automatically, independently controlled. The lights may be manual-on (ADD1) or partial-automatic-on (ADD1), and they must turn off automatically based on either occupancy (ADD2) or a schedule (ADD2).
While energy codes cover new construction and major renovations, coverage is extending to lighting upgrades in existing buildings. ASHRAE/IES 90.1 2013 covers lighting alterations in which more than 10 percent of the connected lighting load is replaced, including lamp-plus-ballast retrofits. Regarding lighting controls, indoor and outdoor lighting must be automatically turned off or reduced when not needed. The IECC requires all code provisions to be satisfied if more than 10 percent of the luminaires are replaced.
Ongoing harmonization efforts have resulted in similar language and requirements between 90.1 and IECC, but significant differences remain in the details. The latest energy codes are getting stricter and more complicated, particularly with regard to lighting controls.
ASHRAE/IES 90.1 2013 and IECC 2015
Below is a summary of major lighting control requirements in ASHRAE/IES 90.1 2013 and IECC 2015. For each requirement, note that exceptions and additional detail may apply. For more information, consult the applicable standard, actual energy code in effect and the authority having jurisdiction.
Automatic shutoff: With few exceptions, indoor lighting must be turned off when not in use. Options include time-scheduling controls, occupancy sensors and signaling from another building system.
Occupancy sensors are specifically required in a wide range of smaller spaces, such as private offices, classrooms and warehouse aisles. The occupancy sensor must have a maximum time delay of 20 minutes for 90.1 or 30 minutes for the IECC. The sensor must be manual-on or auto-on to 50 percent or less of power.
The IECC specifically requires occupancy sensors that can reduce lighting power by at least 50 percent in warehouse aisles.
Time-based controls are allowed for spaces where occupancy sensors are not required. The control system must have certain features, such as the ability to be programmed for weekends and holidays. The lighting must be manual-on or auto-on to 50 percent or less of power.
Space controls: For loads managed by time-based controls, space controls are required, allowing local user override of the schedule for up to two hours. If a captive key device is used, IECC 2015 states the override may be extended. The switch must be readily accessible to users, but, if necessary, a remote switch may be used if it identifies the lights being controlled. Control zoning for space controls is limited. Manual controls must be capable of light reduction, such as bilevel switching.
Additional space controls are required for special lighting types, such as guest rooms and accent lighting. These space controls ensure these loads are separately controlled from the general lighting. For guest rooms, the lighting must be turned off based on occupancy.
Automatic light reduction: ASHRAE/IES 90.1 2013 requires general lighting in certain applications to be automatically reduced by at least 50 percent when not in use. This would be achieved using occupancy sensing with a maximum 20-minute time delay. Automatic light reduction enables energy savings in spaces where the lights are intermittently occupied but must remain on, such as corridors and stairwells.
Daylight-responsive control: General lighting in daylight areas or zones in designated spaces must be independently controlled from other general lighting in the same enclosed space. These controls must be installed if the load is of sufficient size and sufficient daylight availability is expected.
Daylight areas are designated under toplighting (e.g., skylights) and adjacent to sidelighting (e.g., windows). The dimensions are defined by the applicable energy standard, 90.1 or the IECC. ASHRAE/IES 90.1 2013 requires separate daylight-responsive control in both primary (directly adjacent to sidelighting) and secondary (directly adjacent to primary area) daylight areas.
Both standards require the lighting in daylight areas to be automatically reduced in response to daylight. The control output can be continuous dimming, step dimming or multilevel switching. The controls must be readily accessible to calibrate. The standard may apply limits to how the lighting can be controlled to the zones, such as requiring that general lighting in overlapping toplighted and sidelighted daylight areas be zoned with the controls used for toplighting (90.1).
Parking garages: ASHRAE/IES 90.1 2013 requires time-scheduling control for parking garages. In addition, general lighting, segmented into 3,600-square-foot control zones, must be capable of automatic reduction by at least 30 percent during operating hours using occupancy sensors. Daylight-responsive control is also mandated with specific requirements.
More robust control system: ASHRAE/IES 90.1 2013 provides an incentive to install nonmandatory controls as a way to gain power credits that can be applied to the lighting design if using the space-by-space method. IECC 2015 requires the building designer to implement at least one of six additional energy-efficiency options, two of which are related to lighting. One option is to reduce maximum lighting power allowances by at least 10 percent. The other is to install a digital addressable lighting control system with specific capabilities, features and supporting documentation.
Exterior lighting control: Outdoor lighting must be turned off using an astronomical time switch, light sensor or a combination. Dusk-to-dawn lighting must be turned off based on daylight and automatically reduce power by at least 30 percent during certain hours of the night. Facade and landscape lighting must be turned off at a certain time of night (curfew lighting). Time switches must be capable of retaining their programming and time setting for at least 10 hours during a power loss.
Functional testing: Lighting controls must be functionally tested to ensure they operate in accordance with approved documents. The testing party cannot be directly involved in the project design or construction. Specific requirements are mandated for occupancy, time-based and daylight-responsive controls. The testing party must provide the owner with documentation that verifies the installed controls satisfy the performance criteria.
Documentation: At project conclusion, the owner must be given certain documents about the lighting and control system so they can maintain it. This includes drawings and submittal data, operating and maintenance manuals, a written controls narrative (sequence of operations), and a recommended schedule for inspecting and recalibrating the controls.
Over the past 15 years, energy codes have steadily become more detailed and restrictive. This trend has had an extraordinary impact on demand for lighting controls and product development. Buildings designed to the latest energy codes must turn off or reduce lighting when it’s not used to a fine level of detail, resulting in high energy savings, but also making compliance more complex. As lighting controls become fully expressed in energy codes, subsequent standard-writing will likely focus on clarification and making compliance easier.
For more, consult your local energy office, authority having jurisdiction or the energy standards. ASHRAE/IES 90.1 2013 and IECC 2015 may be purchased at TechStreet.com. The Lighting Controls Association offers a free online course summarizing control requirements in these codes at its Education Express system at LightingControlsAssociation.org.