How to use LEED v4 for lighting controls
- Review the new lighting control requirements within U.S. Green Building Council’s LEED v4.
- Understand associated interdependencies of the various prerequisites and credits within the standard.
- Provide guidance in implementation and documentation of LEED v4 project.
The lighting requirements in LEED v4, governed by the U.S. Green Building Council (USGBC), have become much more holistic with a greater emphasis on improving the quality of illumination for the occupants of a building. The associated new metrics for lighting within the standard represent a steep learning curve. The lighting credits include new criteria, such as lamp life, color rendering, reduction in the use of direct-only lighting, surface reflectance within a room, illumination uniformity ratios, etc. Lighting controls, while part of the prerequisite and credit options, are relatively straightforward as compared with these other new requirements.
The new lighting control requirements within LEED v4 will be reviewed to understand associated interdependencies of the various prerequisites and credits within LEED v4, and help provide guidance in implementation and documentation. While this article focuses on LEED v4 for Interior Design and Construction (ID+C), the general concepts are usually applicable for all versions of the rating system. As we will see, LEED v4 does not represent a monumental change in lighting control requirements as compared with those incorporated into the prevailing energy codes. It is vital to understand the new criteria in LEED v4 in order to create a successful LEED submission.
LEED prerequisites and credits for lighting controls
The format and organization of LEED prerequisites and credits have changed between LEED 2009 and v4. While the general classifications have not changed much (for example, "Energy & Atmosphere," "Indoor Environmental Quality," etc. are still present), the numbering of the various individual credits and prerequisites has been eliminated from the project-checklist spreadsheets published by USGBC. Referring to EAc1.2 (which referred to Lighting Controls under LEED 2009) is no longer allowed; the actual title needs to be referenced for that particular credit. While many independent online references have assigned numbers to the various credits to aid in organization, they do not appear in the authoritative USGBC LEED v4 checklists.
The impact of lighting controls in LEED v4 doesn’t extend much beyond what was commonly considered under LEED 2009. The following is a list of prerequisites and credits where lighting controls apply:
- EA: "Fundamental Commissioning and Verification" (prerequisite)
- EA: "Enhanced Commissioning" (credit)
- EA: "Optimize Energy Performance" (prerequisite)
- EA: "Advanced Energy Metering" (credit)
- EA: "Demand Response" (credit—BD+C and O+M rating system only)
- EQ: "Interior Lighting" (credit).
Lighting controls is one potential component of an overall strategy to consider when the building systems are designed to allow for adaptive reuse over the lifecycle of the building structure.
Defining the baseline for energy performance
LEED mandates a minimum level of energy performance. The baseline reference energy-conservation code for LEED v4 is ASHRAE 90.1-2010: Energy Standard for Buildings Except Low-Rise Residential Buildings. This is compared against ASHRAE 90.1-2007, which used LEED 2009. While not necessarily as stringent as more recent versions of ASHRAE 90.1, the U.S. Department of Energy (DOE) performed a study indicating that ASHRAE 90.1-2010 still represented a potential average improvement of 18% across all building types as compared with ASHRAE 90.1-2007.
All LEED projects must comply with all applicable mandatory provisions of ASHRAE 90.1-2010. To meet the LEED "Optimize Energy Performance" prerequisite, it must be demonstrated that there is an improvement in the proposed performance beyond the baseline rating as defined by ASHRAE 90.1-2010. LEED v4 for ID+C projects provide two different compliance-path options; energy-modeling compliance path where a minimum of a 3% improvement is required for the systems related to the area of work, or a prescriptive compliance path where a 5% reduction in the connected lighting power density is required. The 5% reduction may be calculated using either the space-by-space method or the whole-building lighting power allowance. Credit points for additional lighting power reductions are also possible including 10% for one point, 15% for two points, 20% for three points, and 25% for four points.
The LEED prerequisites state that Energy Star appliances, office equipment, electronics, and commercial food-service equipment account for at least 50% (by rated power) of the total Energy Star-eligible products in the project. It is worth mentioning that while there is an Energy Star category for commercial lighting, it does not apply to LEED. HVAC, lighting, and building envelope products are specifically excluded. While outside of the scope of this article, Energy Star certification has been recently extended to several other product categories, such as uninterruptable-power supplies (UPS) and network and computer server equipment. LEED review comments may include requests to quantify these new categories of Energy Star-eligible equipment that are included in projects.
If the energy-modeling compliance path is chosen, selection of lighting controls can help improve the model’s overall performance. While credit is not given for spaces where ASHRAE 90.1 already requires automatic controls, credit can be taken if furnished for spaces where use of specific types of controls is optional (i.e., multilevel occupancy sensors, daylight-adaptive dimming, etc.). Typically, the result is an adjustment that allows the reduction in the connected lighting power usage by a control factor (cf) as defined by ASHRAE 90.1-2010, Table 9.6.2. Note that in 2012, Table 9.6.2 replaced Appendix G, Table G3.2, which listed power-adjustment percentages for automatic lighting controls in Addendum cg. The control factors listed in Table 9.6.2 are much more comprehensive than Table G3.2. Table 9.6.2 also can be used to provide an additional lighting power allowance for the prescriptive path, which can be a significant contribution when attempting additional LEED credit points for lighting power reduction.
The work associated with creating an energy model is not trivial, and the associated cost is not justifiable for many projects. In those cases, the reduced documentation requirements of the prescriptive-compliance path make more sense. For prescriptive compliance in ID+C, a simple checklist of lighting control code requirements per ASHRAE 90.1-2010 is required. BD+C forms are even more basic and omit any type of lighting controls information within the online EA minimum energy-performance forms. Instead, BD+C prescriptive paths need only upload supporting compliance documentation with either the ASHRAE Advanced Energy Design Guide or Advanced Building Core Performance Guide.
In comparison with ASHRAE 90.1-2007, ASHRAE 90-1.2010 has more stringent lighting control requirements that apply to more space types. However, the control requirements are still relatively straightforward. The following are general minimum lighting controls required by ASHRAE 90.1-2010:
- Automatic lighting shutoff controls are required in all spaces (with some special exceptions). Controls may be either time-of-day, occupancy sensors, or a signal from another control or alarm system that indicates that the area is unoccupied.
- Automatic control devices shall be either manual-on (i.e., semi-automatic or vacancy-sensing) or shall turn on lighting to not more to 50%. The primary exception to this rule is where manual-on operation could endanger safety or security.
- Each space enclosed by floor-to-ceiling partitions shall have independent control for the lights with that space. The control shall be readily accessible and located so as to allow the occupants to see the controlled lighting.
- Each control device shall control no more than 2,500 sq ft for a space of 10,000 sq ft or less and a maximum of 10,000 sq ft for a space greater than 10,000 sq ft.
- Controlled lighting shall have at least one control step between 30% and 70% in addition to all-off. This can be accomplished via dimming, alternate switching of fixtures, turning off individual lamps within a multilamp fixture, etc.
- Automatic daylighting controls with multilevel control (including dimming) for side-lighted areas exceeding 250 sq ft or areas with top lighting exceeding 900 sq ft.
- Space with multiscene control systems, shop and lab classrooms, areas that require 24-hour lighting, or where automatic shutoff would endanger safety or security are exempt.
Several states have already adopted energy-conservation codes more stringent than ASHRAE 90.1-2010. If adopted by the local authority having jurisdiction, the more stringent code takes precedence. However, the additional control requirements in those more current energy-conservation codes can translate to additional credit points under LEED.
The optimize energy-performance prerequisite
The Energy and Atmosphere "Optimize Energy Performance" ID+C prerequisite form also includes fields for "Interior Lighting Control" credits. Inclusion of daylight controls for at least 25% of the connected lighting load is worth one point. Inclusion of occupancy controls for at least 75% of the connected lighting load is worth another point. These points are in addition to the potential credit points offered by the environmental quality (EQ) "Interior Lighting" credit.
Filling out the portion of the form related to lighting controls is relatively straightforward (Figure 1). However, additional documentation beyond just filling out the form is required. Typically, you will want to prepare a floor plan specific to lighting controls, with the primary goal of assisting the LEED reviewer in easily visualizing the relative percentage of areas and associated light fixtures controlled by each control type. The floor plan should indicate the room-name identification, space type, and lighting control type used in that area along with the location of the associated controls. The information should be presented in a clear and concise manner-visualization strategies, such as color-coding rooms on the floor plan to identify the control type that is present in each room, may help (Figure 2). The information that is presented on these plans should be easy to cross-reference with information entered on the form. Remember that the LEED reviewer will be seeing this information for the first time and will not have the same intimate familiarity with the project as the design team. Anything that you can do to make it easier for the reviewer to understand the design methodology will help. The floor plan that you create can also be used for the EQ "Interior Lighting" credit if you choose to pursue it.
EQ interior lighting credit
Providing a comfortable and visually pleasing environment with high-quality lighting has a greater emphasis in LEED v4. USGBC has rewritten and expanded the LEED 2009 IEQc6.1 "Controllability of Systems—Lighting" credit. Under LEED 2009, the credit’s only requirement was to provide individual lighting controls for a minimum of 90% of individual occupants and 100% of multioccupant spaces to enable adjustments to suit individual task needs and preferences. Achieving this credit was worth one point. The new LEED v4 EQ credit "Interior Lighting" has expanded that to two potential credit points. There are two credit options to choose from, each of which is worth one point. Option 1 involves providing lighting controls above and beyond ASHRAE 90.1-2010. Option 2 offers eight strategies involving the quality of illumination, of which four must be implemented to meet the minimum credit threshold. Both options can be pursued for credit.
For the lighting controls option, the basic requirement of providing at least 90% of individual occupants with lighting controls remains. However, it has been expanded with a requirement that at least three lighting levels (on, off, midlevel) are also provided. The midlevel must be 30% to 70% of the maximum illumination level. Daylight contributions shall not be included in that assessment. Any daylight contribution does not qualify as a separate lighting level. While motorized window treatments may be useful elsewhere within the rating system, they have no impact for this credit.
In open-office environments, task lighting may still be used to satisfy the individual control requirement. Task lights are not required to be hardwired to meet this requirement-plug-in type may be used. The multilevel control requirement also applies to shared multi-occupant spaces, such as conference rooms and classrooms. For both individual and multi-occupant spaces, the percentage of compliant spaces is based on the number of occupant spaces, not percentage of overall floor area per usage type.
Another requirement is that the controls are in a location that is "convenient" to the occupants. This means that the control is readily accessible and located so that occupants can see the controlled lighting. For example, in health care projects, there must be considerations for patient areas-the controls need to be accessible from the patient bed. There are exceptions to this requirement for certain space types that don’t fall into the categories defined by ASHRAE 90.1-2010, Section 188.8.131.52b. Per the exception to Section 184.108.40.206.2c:
The format for the "Interior Lighting" credit form is similar to the old LEED 2009 credit form. The form still separates individual occupant and multi-occupant spaces due to differences in the minimum compliance thresholds (90% versus 100%). The individual spaces must still be tabulated into specific groups (open-plan workstation, private office, etc.). The various group types are defined via pull-down menus in the PDF credit form. For spaces not matching any of the predefined options, there is an "other" category in the pull-down menu. The shared multi-occupant section of the form has an additional column, "Meets Requirements for Switch Controls." As described in the fine print immediate below the schedule, this means that manual controls must be located within the space and have a direct line of sight to the controlled luminaries.
As with the EA prerequisite, providing proper supporting documentation to this credit is critical. While the most effective strategies for documentation are debatable, ultimately the basic goal should be to clearly and concisely convey to the reviewer what controls are present in which area. New additions to the credit form include a section requiring a written narrative description explaining how individual occupant spaces and shared multioccupant spaces were determined, if certain spaces were excluded and why, and the overall lighting control strategies used for the project. Any floor plans that are submitted should support this information that’s entered into the credit form. Again, it may be effective to expand on the documentation submitted for EA "Optimize Energy Performance" lighting controls category. Make sure that all supporting information is uploaded so that the reviewer doesn’t have to reach out to you to request it.
Commissioning is fundamental
The most energy-efficient light fixture is the one that doesn’t turn on when it isn’t needed. However, what happens when the lighting controls don’t work as expected and the lighting either doesn’t turn off or turns off when it needs to stay on? LEED v4 specifically requires lighting control systems commissioning to address these types of issues. The LEED v4 commissioning requirements are not particular unusual and encompass the traditional documentation and functional testing that was generally required in LEED 2009. Most of the work is associated with the fundamental commissioning prerequisite, and the enhanced commissioning concerns the commissioning authority (CxA). However, a significant amount of input from the design team is still required. The basic documentation requirements for the design team, in addition to the general basis-of-design system narrative, should include the following:
- Develop a sequence of operation for the lighting controls. This should harmonize with the narrative description included with the EA "Lighting Controls" credit documentation.
- Where other credits are pursued (i.e., "Demand Response," "Advanced Energy Metering," etc.), all associated aspects of the interface of the lighting controls to those systems should also be included in the documentation.
- Include required setpoints (light levels for multilevel dimming system, daylit zones, etc.) and run time schedules where time-of-day controls are specified. Again, these should harmonize with the documentation furnished for the other lighting control prerequisites and credits.
- Preventative maintenance plan based on the manufacturer’s recommendations.
- Provide all of the project-specific system manuals-not just the manufacturer’s generic equipment manuals.
- If monitoring-based commissioning is performed for credit under the "Enhanced Commissioning" credit, all aspects of the building energy-usage measurement system including the lighting must be included.
Advanced energy meter and demand response
By having reliable, quantifiable data on the energy usage and performance of the building, it is more likely that persistent or improved energy efficiency can be achieved. After all, it’s difficult to improve what you can’t measure. LEED v4 has an EA credit for "Advanced Energy Metering." The credit requires that any energy end use that represents 10% or more of the total annual energy consumption must be measured. Lighting systems typical fall under this requirement.
Many modern lighting controls systems using a centralized server are able to meet this metering requirement. The two typical compliance solutions are extrapolation and actual measurement. The extrapolation method is based on the assumption that a predefined light fixture power usage multiplied by the measured run time for those lighting fixtures will be representative of the actual energy usage (i.e., a 100 W lamp multiplied by 100 hours of run time equals 10 kWh). By monitoring how long a particular lighting zone is "on," the power usage can be determined if it is known what/how many light fixtures are connected to that control zone.
While it is a cost-effective approach due to its reduced hardware/metering equipment requirements, this methodology only provides an estimate of energy usage. This is due to the fact that it doesn’t depend on direct measurements of the lighting branch-circuit current draw. The accuracy of the estimated energy usage is directly dependent on the accuracy of the predefined quantity of power required by any particular control zone. If dimming is used, ongoing modifications/remodeling work is causing a change in the quantity or type of light fixtures, or other similar variables are anticipated that would impact the accuracy of the extrapolated data, this methodology is not recommended. In that case, use of a true electrical metering system incorporating current transformers to measure current draw at the branch-circuit level would be justified. Some energy-metering and measurement systems will use a hybrid combination of these two methods to achieve some level of cost savings.
If provided, lighting system metering can also potentially contribute to the pilot credit "Energy Performance Metering Path." The goal of this pilot credit is to validate the energy-usage reduction that was estimated by the energy model created for Option 1 of the EA "Minimum Energy Performance" prerequisite.
Also, when a centralized server is used for lighting control, other features, such as utility demand-response programs, are much easier to implement. LEED v4 offers an EA credit for "Demand Response." However, this credit is only available under the BD+C and the O+M rating systems. It is not available for ID+C projects. When demand response is implemented, the functionality of these systems has to be verified through the "Fundamental Commission" prerequisite.
Lighting control requirements span several different LEED prerequisites and credits. Most prerequisites can be easily met through compliance with the prescriptive requirements of ASHRAE 90.1-2010. However, LEED v4 has evolved beyond a simple emphasis on specifying the basic parts of a lighting control system. LEED v4 brings a renewed emphasis on functional testing of lighting control systems to make sure that they function properly. Lighting control systems play a fundamental role in LEED’s core concepts of environmental responsibility and providing building occupants with the ability to control their environment. They cannot be left as an afterthought in designs.
John Yoon is a lead electrical engineer at McGuire Engineers Inc. and is a member of the Consulting-Specifying Engineer editorial advisory board.