A large majority of commercial building energy codes in the United States are based on either the ASHRAE/IES 90.1 energy standard or the International Energy Conservation Code (IECC) model code. Both feature increasingly stringent requirements for lighting controls. This article describes 90.1 and IECC and focuses on specific lighting control requirements in the 2010 version of 90.1 and the 2012 version of IECC, which are being adopted.

The mechanics of 90.1

ASHRAE/IES 90.1, Energy-Efficient Design of New Buildings Except Low-Rise Residential Buildings, produced jointly by the American Society of Heating, Refrigerating and Air-­Conditioning Engineers (ASHRAE) and the Illuminating Engineering Society (IES), was first published in 1975. This energy standard was updated in 1980, 1989, 1999 and 2001. After 2001, it entered a regime of updates every three years. The latest version was published in 2013 (see page 65 for 2013’s changes).

The IECC is a model residential and commercial building energy code produced by the International Code Council (ICC). First published in 1998, the IECC was updated in 2000, 2003, 2006, 2009 and 2012.

Neither 90.1 nor IECC are enforceable codes. Instead, they provide templates for legal jurisdictions to implement an energy code. These jurisdictions may adopt 90.1 or IECC in whole or in part, or they may modify it based on local needs.

ASHRAE/IES 90.1 became the national energy reference standard in 2002. The latest national energy reference standard is the 2013 version of 90.1. As of October 2013, the Department of Energy (DOE) requires all states to adopt a commercial building energy code at least as stringent as the 2010 version of the standard or justify why they cannot comply. On Sept. 26, 2014, the DOE recognized the 2013 version; states have two years to comply.

Thirty-four states complied with these rulings; as of November 2014, 13 of these states and the District of Columbia adopted a code equivalent in stringency to 90.1 2010. The rest still use a code at least as stringent as the 2007 version (see Figure 1).

Many states adopt the IECC; the 2012 version is considered equivalent to the 2010 version of 90.1. The IECC references 90.1 as an alternative compliance standard, providing some flexibility. However, prior to IECC 2009, designers were able to select their compliance standard by section; in the 2009 and 2012 versions of IECC, designers must select a single standard for total compliance, reducing the flexibility of choice and, potentially, the use of 90.1.

The lighting section of ASHRAE/IES 90.1 includes both mandatory and prescriptive provisions. The mandatory provisions cover automatic shutoff controls, space controls, additional controls and other specified items the designer must do. The prescriptive provisions establish limits for maximum lighting power for spaces and buildings, and the designer has a choice about how to design within those limits.

Mandatory lighting control requirements

ASHRAE/IES 90.1 2010 and IECC 2012 contain significant mandatory provisions related to lighting controls. Below is a summary of the major requirements; for specifics, including exceptions applicable to many of the below provisions, consult the appropriate standard or model code.

Automatic interior lighting shutoff, sections 9.4.1, and (ASHRAE/IES 90.1 2010) and C405.2.2.1 and C405.2.2.2 (IECC 2012): Lighting systems in indoor spaces must be turned off when not in use. This provision can be satisfied through the use of a schedule-based control device or system, on occupancy sensor, or a signal from another control or alarm system indicating the space is unoccupied.

Both 90.1 2010 and IECC 2012 require occupancy sensors as the automatic shutoff method in certain spaces, with some exceptions, such as spaces where multiscene controls (e.g., dimming) are used (90.1). The occupancy sensor must turn the lights off within 30 minutes (60 minutes for guestroom bathrooms in 90.1). ASHRAE/IES 90.1 2010 allows timer switches to be used instead of occupancy sensors where preferred.

Where schedule-based controls are used, local switches must be provided allowing users to override the shutoff. The override period is limited to two hours; the IECC allows a longer override if a captive key device is used. An independent program schedule must be established for each 25,000 square feet of space or not more than one floor (90.1).

All automatic lighting controls must be manual-on or turn the lighting on to no more than 50 percent of rated power. Note ASHRAE/IES 90.1 2010 requires automatic shutoff controls be installed in new construction and retrofits in which at least 10 percent of the connected lighting load is replaced. This applies to outdoor and indoor lighting.

Interior space controls, sections (ASHRAE/IES 90.1 2010) and C405.2.1 and C405.2.2 (IECC 2012): Each enclosed space must have at least one independent lighting control device. Options include manual on/off and dimmer switches, occupancy sensors, and timer switches. Energy standards encourage space controls that are readily accessible to users but permit remote switches that are clearly labeled and indicate the status of the lights.

Only the local lighting should be controlled, with specific limits for control zoning. For 90.1 2010, the maximum area controlled per switch is 2,500 square feet (if the enclosed space is 10,000 square feet or smaller) or 10,000 square feet (if the enclosed space is larger than 10,000 square feet). For IECC 2012, the maximum area is 5,000 square feet unless it is a larger application, such as a mall or industry facility, in which case the limit is 20,000 square feet.

All manual controls must allow users to select a light level between full on and off. For 90.1 2010, at least one control step must be provided between 30 and 70 percent of rated lighting power in the space. For IECC 2012, at least one control step must be provided at 50 percent. This can be accomplished using continuous or step-dimming or A/B switching of independently circuited ballasts or luminaires. IECC requires the resulting illumination pattern to be relatively uniform across the space.

Additional space controls, section (ASHRAE/IES 90.1 2010) and C405.2.3 (IECC 2012): Additional space controls are required for special lighting types, ensuring they are controlled independently from other lighting in the space. These include display/accent/display case, guestroom, supplementary task and nonvisual (e.g., food warming) lighting as well as lighting intended for demonstration or sale.

Daylight harvesting control, sections and (ASHRAE/IES 90.1 2010) and C405.2.2.3 (IECC 2012): General lighting installed in daylight zones must be independently controlled from other general lighting. The first step is to determine the daylight zones, which can be found in the Definitions section of 90.1 (“daylight area,” “primary sidelighted area” and “secondary sidelighted area”) and IECC (“daylight zone”). IECC defines the dimensions of daylight zones adjacent to skylights and vertical fenestration (e.g., windows), while 90.1 also includes rooftop monitors.

The next step is to determine whether the standard requires independent control for the lighting in the defined daylight zone. If a combined primary sidelighted area is less than 250 square feet, a toplighted daylight area is 900 square feet or less, or a toplighted area is less than 1,500 square feet in a building in Climate Zone 8, 90.1 exempts it from daylight harvesting control. If two or fewer luminaires are in the daylight zone, IECC exempts it.

Next, identify appropriate controls. Options for automatic daylight harvesting control include 1). continuous dimming with a 100 percent to less than 35 percent light output range or 2). automatic multilevel controls offering full power, a step between 50 and 70 percent, and another step between off and less than 35 percent. The calibration adjustment must be easily accessible and not at the photosensor itself. IECC also provides a manual control option for daylight zones that can be satisfied with at least one switch or dimmer switch.

The final step is to zone the controls within the daylight zone or area. IECC limits the size of daylight harvesting control zones to 2,500 square feet. Control zones may encompass contiguous daylight zones as long as these daylight zones do not face more than two adjacent directions (e.g., north and east). Toplighted daylight zones more than 15 feet from the perimeter must be controlled separately from sidelighted daylight zones.

Stairwells and parking garages, sections and (ASHRAE/IES 90.1 2010): ASHRAE/IES 90.1 2010 requires occupancy sensor-based lighting-reduction controls in stairwells and parking garages. This ensures the lighting remains on when needed but reduces energy consumption during times when the space is unoccupied.

Stairwell lighting must be controlled so that the lighting power can be reduced by at least 50 percent within 30 minutes of the space being unoccupied, which would require remote or luminaire-integrated occupancy sensors. Similarly, lighting power must be reduced within 30 minutes by at least 30 percent in parking garages, with control zones limited to 3,600 square feet. Additionally, luminaires installed within 20 feet of walls with a certain net opening-to-wall ratio, and no nearby exterior obstructions, must automatically reduce power consumption during times of daylight availability.

Power adjustment credits, section 9.6.2(c) and table 9.6.2 (ASHRAE/IES 90.1 2010): When using 90.1’s space-by-space method for demonstrating lighting-power-density compliance, ASHRAE/IES 90.1 2010 offers designers new lighting power adjustment credits based on use of advanced lighting control strategies in certain offices, meeting spaces, education spaces, retail sales areas and public spaces. Qualifying technologies range from manual dimming control to automatic continuous daylight harvesting dimming with power adjustment factors, which are applied to the controlled lighting load of 5–30 percent.

Outdoor lighting control, sections (ASHRAE/IES 90.1 2010) and C405.2.4 (IECC 2012): Outdoor lighting must be turned off when it is not used. ASHRAE/IES 90.1 2010 requires all outdoor lighting be controlled by a photosensor. Building facade and landscape lighting also must be controlled by an astronomical time switch that turns the lights off at a certain time of night. Lighting that is not facade and landscape lighting must be controlled by a device that reduces lighting power by at least 30 percent either during a certain time of night (scheduling) or during any period when no activity has been detected for at least 15 minutes (occupancy sensing). The standard explicitly states this requirement also applies to advertising signage. IECC 2012 requires an astronomical time switch or photosensor for dusk-to-dawn lighting and either an astronomical time switch or combination photosensor/time switch for all other lighting.

Both 90.1 2010 and IECC 2012 require that time switches retain their programming and time setting for at least 10 hours during a power loss.

Functional testing, section 9.4.4 (ASHRAE/IES 90.1 2010) and C408.2.5.4 and C408.3 (IECC 2012): Functional testing is required for installed lighting controls. These requirements were included to ensure that the controls operate as specified. Placement and calibration of occupancy and photosensors, as well as time scheduling programming, must be confirmed as being installed and set up in accordance with approved documents and manufacturer instructions.

The construction documents must identify who will perform and verify the testing. The testing party cannot be directly involved in the design or construction of the project. IECC 2012 further requires that a commissioning report will be delivered to the owner providing test procedures and acceptance criteria, results, deficiencies and corrective action taken.

Documentation, sections 9.7 (ASHRAE/IES 90.1 2010) and C4082.5 (IECC 2012): 
At the conclusion of the project (within 90 days of acceptance of the lighting system for 90.1 or upon receipt of a certificate of occupancy for IECC 2012), the owner must be given certain documentation about the lighting and control system so that they can maintain it. This documentation must include as-built drawings of the lighting and control system, submittal data for each lighting and control item, operating and maintenance manuals for all lighting equipment, schedule for inspecting and recalibrating lighting controls, and a complete narrative of how each lighting control is supposed to operate, including recommended settings.

ASHRAE/IES 90.1 2013

The next generation of ASHRAE/IES 90.1, published in 2013, further strengthened the standard’s lighting control requirements.

• Occupancy sensors must be set to turn the lights off within 20 minutes (instead of 30 minutes) after a space is vacated.

• Automatic independent control is now required in secondary sidelighted daylight zones (covering additional luminaires farther from the windows) rather than just incentivized with a control credit.

• Daylight-harvesting step-dimming control now requires two control points between off and full-on—one dim level between 50–70 percent of design power and one between 20–40 percent—to provide greater flexibility.

• A second automatic lighting shutoff option is required for certain occupancy sensor installations—partial-off to 50 percent of design power within 20 minutes of the space being vacated—in spaces where the lights are periodically not needed but must remain on.

More detailed functional testing requirements are imposed.

The biggest change in the 2013 standard is a new table (Table 9.6.1) format for determining lighting power density allowances using the space-by-space compliance method and minimum mandatory control requirements using either the space-by-space or building-area compliance methods. This was included to make the standard’s requirements easier to reference to facilitate compliance.

Regulated design

The next version of the IECC is expected to be published in 2015, and the next version of 90.1 the year after that. The 2016 version of 90.1 is expected to focus on usability, with potentially an optional simplified method to facilitate adoption. As light-emitting diode technology continues to develop, lighting power densities will also likely decrease. While demand response is growing in California’s Title 24 energy code, it is unlikely to be required in 90.1. Further, despite interest in switching from a power- to an energy-based code is seen as a path to more creative control design, a practical way of accomplishing a truly energy-based lighting design standard has not yet been conceived.

While it is difficult to speculate on the future, it is relatively easy to identify past trends. The major trends have increased stringency and complexity, in particular in regards to falling maximum power allowances and broader mandatory requirements for lighting controls. The challenge now is to simplify the standard to make these requirements more understandable and achievable. Control requirements have trended toward more smaller control zones, multilevel control and daylight harvesting, supported by commissioning, all of which create new business opportunities for electrical contractors with the right know-how.