Commercial building energy codes regulate the designed energy efficiency of nonresidential buildings. Current codes and standards require a broad range of lighting controls to ensure general lighting is turned OFF or reduced when it is not needed.
In the United States, the majority of energy codes are based on 1) the 90.1 energy standard, published by ASHRAE and the Illuminating Engineering Society, or 2) the International Energy Conservation Code (IECC), published by the International Code Council, each of which are updated every three years. Some states, such as California, develop unique codes.
This article provides general introductory knowledge about the lighting control requirements imposed by the 2016 version of ASHRAE/IES 90.1 and the 2018 version of the IECC (as initially published, without addenda).
The material is provided for general educational purposes only. For complete information, consult the applicable standard/energy code and the authority having jurisdiction. To learn more about the specific energy code applicable to your jurisdiction, contact your local energy office.
ENERGY STANDARDS
ASHRAE/IES 90.1, Energy Standard for Buildings except Low-Rise Residential Buildings, was developed as a model energy code that jurisdictions can adopt in whole or in part. It is updated every three years (1999/2001, 2004, 2007, 2010, 2013, 2016, 2019).
In February 2018, the U.S. Department of Energy ruled ASHRAE/IES 90.1-2016 as the national energy reference standard, which required all states to adopt a code at least as stringent by February 2020, or justify why they cannot comply.
The International Energy Conservation Code (IECC) is a model residential and commercial building energy code updated every three years (2000, 2003, 2006, 2009, 2012, 2015, 2018). The IECC references ASHRAE/IES 90.1 as an alternative standard, providing a choice to building designers.
Image courtesy of EnergyCodes.gov, as of December 2018.
LIGHTING AND CONTROL REQUIREMENTS AT A GLANCE
ASHRAE/IES 90.1-2016 and IECC 2018 impose prescriptive and mandatory requirements for lighting systems. A broad range of lighting controls is required, which must be functionally tested and documented. The design power must not exceed imposed maximums. Documentation related to the lighting and control system must be turned over to the owner.
NEW VERSUS EXISTING BUILDINGS
Sections 9.1.2 (90.1-2016) and C503 (IECC 2018)
The lighting controls provisions in ASHRAE/IES 90.1-2016 cover interior and exterior lighting alterations in existing buildings. These are operations in which the lighting system is replaced. In these situations, all interior control provisions must be met where applicable except daylight-responsive control, and all exterior control provisions must be met. This standard’s automatic shutoff control provisions also cover alterations in which >20% of the connected lighting load is replaced, including lamp-plus-ballast retrofits.
IECC 2018 states that lighting alterations in existing buildings must satisfy all of Section C405’s provisions (which also apply to new construction). An exception is where less than 10% of the luminaires are replaced and these new luminaires do not increase the installed interior lighting power.
GENERAL EXEMPTIONS TO LIGHTING CONTROL REQUIREMENTS
Sections 9.1.1 (90.1-2016) and C405.2 (IECC 2018)
Both 90.1-2016 and IECC 2018 contain broad and detailed mandatory lighting control requirements. However, some general exemptions apply.
For 90.1, exemptions include emergency lighting that is automatically OFF during normal building operation, decorative gas lighting, lighting required by life/safety regulation or law, and exterior lighting not fed by the building’s electrical service.
For IECC, exemptions include 24-hour emergency or security lighting, emergency egress lighting that is OFF during normal building operation, and lighting for interior egress stairwells, exit ramps, and exit passageways.
Otherwise, each provision in the standard may include its own specific exemptions.
COMPLIANCE PATHS (IECC 2018)
Section C405.2 (IECC 2018)
IECC 2018 provides two paths for interior lighting controls compliance, one based on luminaire-level lighting controls (LLLC), and the other based on using remote devices. IECC defines LLLC as a “lighting system consisting of one or more luminaires with embedded lighting control logic, occupancy and ambient light sensors, wireless networking capabilities, and local override switching capability, where required.”
INTERIOR SPACE CONTROLS
Sections 9.4.1.1 (90.1-2016) and C405.2.1 and C405.2.2 (IECC 2018)
Each enclosed space must have at least one control device that independently controls general lighting in the space. This may include manual switches, occupancy sensors with integral manual-OFF (and ON) switch, and manual-ON timer switches. The area controlled by the switch is restricted.
LIGHT REDUCTION SPACE CONTROL
Sections 9.4.1.1(d) (90.1-2016) and C405.2.2 (IECC 2018)
Installed interior manual controls must be capable of lighting power reduction allowing users to select a light (and power) level between full ON and OFF. This may be accomplished with continuous or step dimming or A/B switching of alternate luminaires, luminaire rows or ballasts. IECC requires that the resulting illumination pattern be relatively uniform.
AUTOMATIC SHUTOFF OF INTERIOR LIGHTING
Sections 9.4.1.1 (90.1-2016) and C405.2.1 and C405.2.2 (IECC 2018)
With few exceptions, interior lighting must be turned OFF when it is not in use, with users having the ability to manually turn the lights OFF as well. Compliant options include lighting controls with scheduling capability, occupancy sensors, and signaling from another building system.
The sensor must be manual-ON or auto-ON-to-<50% of power unless otherwise permitted. 90.1 makes an exception for manual-ON if such operation would endanger safety or security. 90.1 states that open-plan office lighting can automatically turn ON to more than 50% as long as the control zone is no larger than 600 sq.ft. (which would typically involve occupancy sensors).
OCCUPANCY-BASED AUTOMATIC SHUTOFF
Sections 9.4.1.1(g) and (h) (90.1-2016) and C405.2.1 (IECC 2018)
Occupancy sensors may be used in any appropriate interior space to satisfy requirements for automatic shutoff, but are specifically required in a range of spaces.
OCCUPANCY-BASED AUTOMATIC SHUTOFF
Sections 9.4.1.1 (90.1-2016) and C405.2.1 (IECC 2018)
When using occupancy sensors, the lights must turn OFF within 20 minutes of the space being vacated. If an occupancy sensor is used, a separate manual space control is not required. However, the occupancy sensor must feature a manual ON/OFF switch.
OCCUPANCY SENSORS IN WAREHOUSES (IECC)
Sections 9.4.1.1 (90.1-2016) and C405.2.1.2 (IECC 2018)
ASHRAE/IES 90.1-2016 requires that warehouse storage lighting be automatically reduced when it is not in use. Specifically, lighting power must be reduced by at least 50% within 20 minutes of vacancy.
IECC 2018 requires that occupancy sensors be used in warehouses in open areas and aisles. These sensors must automatically reduce lighting power by at least 50% when areas are unoccupied. Each aisle must be separately controlled. Sensors controlling aisle lighting must not control lighting outside the aisle.
OCCUPANCY SENSORS IN OPEN OFFICES (IECC)
Section C405.2.1.3 (IECC 2018)
IECC 2018 requires that lighting in open office spaces >300 sq.ft. must be divided into 600-sq.ft. control zones. When occupants in a zone vacate, the lighting power must be reduced by at least 80%. When all occupants leave the space, all control zones must turn OFF lighting within 20 minutes.
OCCUPANCY SENSORS FOR LIGHT REDUCTION (90.1)
Section 9.4.1.1 (90.1-2016)
Besides warehouse storage lighting, ASHRAE/IES 90.1-2016 requires lighting in other designated applications be automatically reduced when it is not in use. As with warehouse storage areas, lighting power must be reduced by at least 50% within 20 minutes of the space becoming unoccupied.
PARKING GARAGES (90.1)
Section 9.4.1.2 (90.1-2016)
ASHRAE/IES 90.1-2016 requires both time- and occupancy sensor-based lighting reduction controls in parking garages. This ensures lighting that must remain ON at all times will save energy during times when the space is unoccupied.
TIME-BASED AUTOMATIC SHUTOFF
Section 9.4.1.1 (90.1-2016) and C405.2.2.1 (IECC)
Where occupancy sensors are not specifically required, time-based (scheduled shutoff) controls may be used instead of occupancy sensors. In these spaces, the lighting (which 90.1 clarifies includes all lighting, including lighting connected to emergency circuits) must be capable of being overridden by local space controls. Typically, this would involve a readily accessible manual switch with a two-hour override.
DAYLIGHT-RESPONSIVE CONTROL
Sections 9.4.1.1(e) and (f) (90.1-2016) and C405.2.3 (IECC 2018)
ASHRAE/IES 90.1-2016 and IECC-2018 require that general lighting in daylight areas or zones be independently controlled from other general lighting in the same enclosed space. This will depend on whether the load is of sufficient size and sufficient daylight availability is expected.
The dimensions of these daylight areas or zones can be found in the Definitions section of 90.1 (“daylight area”) and in Section C405.2.3 of the IECC. Both standards establish daylight areas or zones adjacent to toplighting (e.g., skylights) and sidelighting (e.g., windows). For sidelighting, 90.1 imposes requirements for both primary (directly adjacent to vertical fenestration) and secondary daylight areas (directly adjacent to primary daylight areas).
The next step is to select appropriate devices for independent control of the general lighting in these areas or zones. IECC and 90.1 require automatic controls that reduce controlled lighting in response to daylight. The automatic control may be continuous dimming, step dimming, or multilevel switching. The mechanism used to calibrate the photocontrols must be readily accessible.
The final step is control zoning, which involves assigning luminaires to controllers so that they respond simultaneously to the same control input.
OTHER SPECIFIC-APPLICATION CONTROLS
Sections 9.4.1.3 and 9.4.4 (90.1-2016) and C405.2.4 (IECC 2018)
Additional are required for special lighting types, ensuring they are independently controlled from other lighting in the space.
POWER ADJUSTMENT CREDITS (90.1)
Section 9.6.3 and Table 9.6.3 (90.1-2016)
ASHRAE/IES 90.1-2016 provides an incentive to use non-mandatory control options to gain additional wattage that can be used anywhere in the design of the building. These strategies may be applied as long as all mandatory controls are provided. Table 9.6.3 identifies control strategies, space types, and associated power adjustment factors that can be used to calculate additional interior lighting power allowance (Wattage of Controlled Luminaires x Control Factor) if using the Space by Space Method.
ADDITIONAL ENERGY EFFICIENCY (IECC)
Section C406 (IECC 2018)
Buildings designed in accordance with IECC 2018 must enhance energy efficiency by implementing one of eight options. These options cover on-site renewable energy production, HVAC/hot water enhancements, and lighting and controls. For lighting, lighting power be reduced to at least 10% below the model code’s maximum allowance. For lighting controls, enhanced digital controls must be implemented.
EXTERIOR LIGHTING
Sections 9.4.1.4 (90.1-2016) and C405.2.6 (IECC 2018)
Exterior lighting must be turned OFF when it is not used using an astronomical time switch, photosensor, or combination of the two. Dusk-to-dawn and other lighting must be reduced afterhours.
FUNCTIONAL TESTING
Sections 9.4.3 (90.1-2016) and C408 (IECC 2018)
All lighting controls must be set up in accordance with approved documents and manufacturer instructions, and performance must be verified through testing. This ensures that the project team delivers a lighting and control system that operates as specified.
DOCUMENTATION
Sections 9.7 (90.1-2016) and C408 (IECC 2018)
At the conclusion of the project, the owner must be given certain documentation about the lighting and control system so that they can maintain it. This is in addition to documentation provided by the functional testing party that the installed controls meet or exceed specified performance criteria.
CONCLUSIONS
Commercial building energy codes have grown highly restrictive, particularly in regards to lighting and controls. ASHRAE/IES 90.1-2016 and the IECC 2018 contain extensive control requirements that are essentially similar due to harmonization but with some notable differences.
The most common thread is that lighting must be turned OFF or reduced when it is not needed. Occupancy sensors are required in a broad range of spaces, and separate control is required for daylight areas, including, in some cases, secondary areas. The standards impose commissioning requirements including functional testing and documentation. Finally, these standards incentivize installation of a more robust control system as either an enhanced efficiency option or as a method to achieve a higher interior lighting power allowance.
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