LEED v4 updates and impacts on lighting controls
LEED v4 has adopted ASHRAE Standard 90.1-2010, which includes a number of mandatory lighting controls requirements.
- Explore ASHRAE 90.1-2010, the new basis for LEED v4.
- Understand how lighting control design can contribute to LEED v4 points through best practices.
Previous studies have shown that more electricity is consumed for lighting in commercial buildings than for other applications. With tighter operational budgets and enhanced focus on supporting better environmental outcomes, organizations are committed to changing this. LEED v4 supports this aim by using ASHRAE 90.1-2010: Energy Standard for Buildings Except Low-Rise Residential Buildings as a baseline-an updated standard with an aggressive goal of 30% energy-cost savings over the previous standard. To help give an understanding of possible energy-savings related to lighting controls, Lawrence Berkeley National Laboratory (LBNL) published A Meta-Analysis of Energy Savings from Lighting Controls in Commercial Buildings, an analysis of 240 energy savings estimates from 88 papers and case studies, focusing on actual field installations as opposed to simulations. From this data, LBNL produced the best estimates of average lighting energy savings for four primary lighting control strategies (see Table 1).
Update to the energy baseline in LEED v4
In prior versions of LEED, the energy baseline was ASHRAE 90.1-2007. This has now been increased to ASHRAE 90.1-2010. ASHRAE 90.1 is a standard that provides minimum requirements for energy-efficient designs for buildings.
The following is a comparison of ASHRAE 90.1-2007 versus ASHRAE 90.1-2010 for specific highlights as they relate to lighting controls:
Threshold for compliance:
- 2007: Any new or retrofit projects encompassing 50% or greater alteration of the connected lighting load.
- 2010: Any new or retrofit projects encompassing 10% or greater alteration of the connected lighting load.
Automatic shutoff of lighting:
- 2007: Required in buildings larger than 5,000 sq ft.
- 2010: Required in all spaces.
- 2007: Not a requirement.
- 2010: Lighting must be wired to allow for a power reduction of 30% to 70% in addition to turning off the lighting by either dimming or switching.
- 2007: Not a requirement.
- 2010: Daylighting control must be automatic based on natural-light contribution and must be installed in spaces with windows and skylights. ·
- 2007: Lighting must be off during the day.
- 2010: Lighting must be off during the day and must be off or at a reduced level at night.
- 2007: Not a requirement.
- 2010: 50% of receptacles in private offices, open offices, and computer classrooms must be automatically shut off.
There are several control methods available to incorporate the requirements stated above. A networked lighting control system from a building level is one option. Or installing multiple types of systems (e.g., relay control, architectural dimming systems, wall box dimming) is another option. As we will see later, the preferred option may be to use a networked system to maximize the points available in the LEED v4 scorecard.
Contributing to the LEED scorecard
Lighting control strategies can be used to earn a maximum of 32 points in six credits, housed in three credit categories. It should be noted that the maximum points per credit is not just for lighting controls. There are several design factors that will come together in a given credit.
The following gives a brief overview of the credit and a lighting control strategy to implement:
Energy and Atmosphere credit category
Enhanced Commissioning—maximum of six points. (Six points are achieved by following Path 2 and Envelope Commissioning).
Intent of credit: To further support the design, construction, and eventual operation of a project that meets the owner’s project requirements for energy, water, indoor environmental quality, and durability.
Implementation: Develop a design narrative that describes the intent for the lighting control design. This narrative will be used by the commissioning authority to commission the lighting control system and ensure it meets the owner’s requirements.
Optimize Energy Performance—maximum of 18 points:
Intent of credit: To achieve increasing levels of energy performance beyond the prerequisite standard to reduce environmental and economic harms associated with excessive energy use.
Implementation: Comply with ASHRAE 90.1-2010. The following strategies could be incorporated:
- Time/astronomical scheduling: Lighting in a defined area turns on or off, or dims, based on a predetermined, customizable schedule.
- Occupancy/vacancy control: In each area of the building, lighting is turned on or off based on detected occupancy. With vacancy control, users must manually turn on lights, but lights are automatically turned off when a space is vacant. Vacancy sensors are generally considered more efficient than, therefore preferable to, occupancy sensors because they only turn lighting off, not on—users have to turn lights on manually.
- Daylight harvesting: Electric light levels are automatically adjusted to account for the amount of natural sunlight in a space. Appropriate light levels are maintained for functional purposes, and total illumination is evenly maintained throughout the space.
- Task tuning: Maximum light levels are set for a particular use or task in a specific room to prevent overlighting.
- Personal control: Individuals can tailor the lighting in their workspace to their personal preferences.
- Control of emergency egress lighting: In the past, lighting on emergency circuits was often "on" 24/7 as a safety measure, burning through the night long after occupants of a building had left. Advances in control devices now allow emergency lighting circuits to be controlled by time schedules or by automatic sensors. By equipping these devices with a UL 924 emergency transfer device, which can override the digital lighting control system if normal power is lost, the system is able to turn on all lights connected to the emergency circuit and maintain egress levels for occupant safety without wasting energy.
- The lighting control system can be connected to the BAS to use the detection signal of occupancy sensors at all hours to adjust mechanical setpoints. If multiple lighting control zones are provided in a single mechanical system zone, the lighting control system can accumulate the occupancy zones within the mechanical zone to help refine the efficiency of the HVAC system.
Specific area examples include:
- Interior private offices or rooms: Occupants turn lights on and off by pressing a low-voltage wall switch. A ceiling-mounted vacancy sensor turns the room lighting off if occupants forget to turn it off when they leave.
- Perimeter offices or rooms with adequate daylight: Occupants turn lights on and off by pressing a low-voltage wall switch. This switch turns the lights on to a level allowed by a photo sensor that monitors the amount of daylight hitting the exterior of the window glass. A ceiling-mounted vacancy sensor turns off the room lighting if occupants forget to turn it off when they leave.
- Corridors and lobbies: These are the only building areas with two modes of operation: "during business hours" and "after business hours." In the corridors, an array of occupancy sensors turn lighting on and off according to occupancy and the current response mode, dictated by the lighting control system’s time clock. Perimeter areas are also equipped with photo sensors to adjust the amount of electric light based on the amount of daylight in the space. Luminaires in these areas are adjusted to lower-level output when a load-shed signal is sent.
- During business hours: Upon detecting occupancy in a corridor, the lighting control system turns lights on and keeps them on until the system enters "after business hours" mode, after which point it only turns lights on when the building has occupancy, preventing the corridors from lighting up on holidays, snow days, and other low-occupancy days. Once triggered, lighting remains on in the corridor throughout the business day, preventing short on-off cycling of corridor lighting as occupants move from space to space. At the end of "during business hours," the system transfers to the "after business hours" lighting control mode.
- After business hours: Occupancy sensors control corridor lighting via auto-on and auto-off functions. After 15 minutes of non-detection, lighting automatically turns off. Minimum cycling of lighting is expected during these low-occupancy hours. Maximum light levels are set during this time period, as it is anticipated that the full light level will not be needed.
- Restrooms and stair towers: Lighting in these rooms is determined 24/7 by occupancy sensors. After 15 minutes of nondetection, the lighting automatically turns off. Luminaires in these areas are adjusted to lower-level output when a load-shed signal is sent.
- Utility and storage rooms: Occupants turn lights on and off by pressing a low-voltage switch on the wall. A 2-hour timeout sequence starts when the switch is activated. A blink warning occurs when 5 minutes remain in the 2-hour countdown. If the user wants to remain in the room, the switch can be activated again, and another 2-hour timeout sequence commences. Luminaires in these areas are adjusted to lower-level output when a load-shed signal is sent. It is worth noting that NFPA 70: National Electrical Code, Article 100.26 (D), requires a manual switch/override for electrical rooms.
- Conference rooms: Occupants turn the lights on and off by either pressing a low-voltage wall switch or using a preset scene-dimming control station. Ceiling-mounted occupancy sensors operating in vacancy mode turn the lighting off if occupants leave without turning off the lights. Maximum light levels are set for this space for certain tasks.
In order to maximize the credits achieved, it is important to understand the inputs to the energy model, and what is required from the facility owner/occupant. For example, eQuest, is an energy modeling software that can model the time based on lighting control, occupancy control, and daylighting control. For the time-based control strategy, input is needed from the facility’s owner/occupant in regards to the duration of the on/off setting (i.e. – On at 7 a.m., and off at 7 p.m.). In addition, input is needed for the duration of occupancy for certain spaces. For example, offices that are occupied on average for approximately 5 hours per day will need input for the lighting to be on for that duration. Daylighting modeling is done using sophisticated algorithms based on simple inputs of length of window area, depth of the daylit zone, and type of glazing.
Advanced Energy Metering—maximum of one point:
Intent of credit: To support energy management and identify opportunities for additional energy savings by tracking building-level and system-level energy use.
Implementation: Use a networked lighting control system that has energy metering incorporated.
Demand Response—maximum of two points:
Intent of credit: To increase participation in demand-response technologies and programs that make energy-generation and distribution systems more efficient, increase grid reliability, and reduce greenhouse gas emissions.
Implementation: Lighting control can contribute to a buildingwide effort to reduce demand. Lighting is turned off or dimmed in predetermined areas at times of peak demand. A networked lighting control system can receive an initiation signal from a demand-response program provider and will also restore light levels at the end of the demand-response event.
Indoor Environmental Quality credit category
Interior Lighting—maximum of two points:
Intent of credit: To promote occupants’ productivity, comfort, and well-being by providing high-quality lighting.
Requirement specific to lighting control: For at least 90% of individual occupant spaces, provide individual lighting controls that enable occupants to adjust the lighting to suit their individual tasks and preferences, with at least three lighting levels or scenes (on, off, midlevel). Midlevel is 30% to 70% of the maximum illumination level (not including daylight contributions).
Implementation: By using the strategies noted above in the Energy and Atmosphere credit, this credit should be realized.
Innovation credit category
Innovation—maximum of two points:
Intent of credit: To encourage projects to achieve exceptional or innovative performance.
Implementation: Nearly 30% savings have been realized in lighting energy consumption by implementing the control strategies noted above. This has qualified such projects for an innovation credit.
In addition to more advanced lighting control systems, LED technology has helped in being able to meet energy codes and achieve LEED certification. LED technology is increasingly affordable and is being used more frequently. One advantage of LED lighting is that it is inherently dimmable: If you pair the LED’s dimmable driver with a compatible control, additional components are not required to tune the light. The 20% to 30% additional cost is no longer necessary for a controllable fluorescent ballast, opening up the possibilities of light modularity as the norm instead of a novelty.
Rising energy costs and more regulation through energy codes are making energy management a top priority for building owners and managers. This environment emphasizes the importance of LEED-certified buildings. The points noted above give designers and engineers additional tools to both meet and exceed the expectations of current and future energy code regulations.
Illustrated in Table 2, the strategies that are discussed are not frequently used. As lighting and electrical designers become more familiar with the technologies available, energy savings will become much more commonplace.
Robert J. Garra Jr. is a senior vice president at CannonDesign. An engineering leader who understands clients and their goals, Garra applies his project leadership and industry knowledge across the firm’s market segments while providing strategic direction to the engineering group. He is a member of the Consulting-Specifying Engineer editorial advisory board.