How to use LEED v4 for lighting controls

Lighting requirements in LEED v4 have become more holistic, with a greater emphasis on improving the quality of illumination for building occupants.

08/16/2017


 

Learning objectives: 

  • 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

Figure 1: Modern lighting control systems often use digital addressable devices for status and control functions. This picture is of a Dali to DMX control gateway to automate control of tunable white LED light fixtures. Courtesy: McGuire Engineers Inc.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. 

Energy modeling

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. 

Prescriptive compliance

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.

Figure 2: Vacancy sensing lighting controls are a ASHRAE 90.1-2010 requirement for several different space types. This picture is of a ceiling mounted dual technology sensor with an integrated photocell. The DIP switches allow it to be configured as either an occupancy (auto on/auto off) or vacancy (manual on/auto off) sensor. Courtesy: McGuire Engineers Inc.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. 


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