LED codes and standards
- Outline the codes and standards that dictate designing with LEDs.
- Compare and contrast the benefits and drawbacks to LEDs.
- Evaluate the use of lighting controls.
Nearly all commercial facilities in the United States are governed by one of three energy-conservation codes:
- ASHRAE Standard 90.1: Energy Standard for Buildings Except Low-Rise Residential Buildings
- International Energy Conservation Code (IECC) from the International Code Council
- California Title 24: California Energy Code.
For this article, these codes will be referenced as ASHRAE 90.1, IECC, Title 24, and collectively as "the codes."
Each code describes requirements for lighting, in terms of the total lighting power allowed, along with prescriptive requirements regarding lighting controls and operation. Most jurisdictions require that a project design complies with ASHRAE 90.1 or IECC, and California projects are governed by Title 24.
ASHRAE 90.1 can be considered the standard energy code for the United States. The federal Energy Policy Act of 2005 (EPAct), as amended, requires that states adopt an energy code at least as stringent as whatever edition of ASHRAE 90.1 is found to be most stringent by the Department of Energy (DoE). Title 24, directly enforceable only in California, operates to some degree as a bellwether code—significant changes to ASHRAE 90.1 and IECC often appear first in Title 24 and then migrate to future editions of the other two codes.
These codes and their predecessors can exert substantial influence on lighting markets. For example, California Title 20, 1605.1(l), included by reference in California Title 24, requires that exit signs consume no more than 5 W per face, echoing the requirements of the EPAct. That level is difficult to achieve with fluorescent lamps, and impossible with incandescent lamps. The requirement had the effect of creating a de facto requirement for LED drivers in exit signs. Today, practically every exit sign uses LEDs as its light source.
The primary intent of the codes is to ensure that the built environment uses less energy than it would in their absence. One of their secondary purposes is to foster technologies that show promise for future energy conservation. LED lighting currently looks to be one of those technologies, and we can expect the codes to include requirements that foster its development and acceptance to the extent that those requirements are reasonably achievable and don’t conflict with the codes’ primary purpose.
This article isn’t intended to describe how to achieve compliance with these codes. Each code describes a Byzantine maze of decision trees, exceptions, and alternate compliance methods. A thorough treatment of any of them is well beyond the scope of this article. Rather, this article qualitatively describes some of the requirements of the codes covering lighting systems, with particular emphasis on new requirements in common among them, and how those requirements affect design decisions regarding LED lighting.
LED benefits and drawbacks
LED lighting offers a number of advantages over more traditional technologies. They exhibit very long lifetimes as compared with fluorescent lamps, and consequently have lower maintenance requirements. They’re robust and much more resistant to physical damage than fluorescent lamps. They’re insensitive to cycling, and can be energized repeatedly without reducing their life. Their ultraviolet and infrared emissions are extremely low compared with other sources. And, they don’t contain environmentally troublesome ingredients, making their ultimate disposal a simple matter.
LED lighting also brings advantages that are specifically interesting in regard to energy conservation:
- Efficiency: The luminous efficacy of LED luminaires is generally competitive with fluorescent fixtures, and fixtures with high-end LED emitters can exceed the efficacy of the best fluorescent fixtures. In addition to direct energy savings, high efficiency reduces HVAC costs during heating seasons and in interior zones.
- Dimmability: LEDs are easily dimmable, as a consequence of the technology used to provide the constant direct current (dc) that drives them. Adding dimming capability to an LED fixture is inexpensive as compared with fluorescent fixtures.
- Controllability: LEDs come to full brightness almost immediately after they’re energized, while fluorescents can take many seconds or a few minutes to reach maximum output.
- LEDs are much less sensitive to cold temperatures than fluorescent lamps, making them well suited for outdoor use.
At the same time, LEDs bring significant disadvantages:
- LED lighting is generally more expensive than fluorescent lighting in terms of similar effective light output, build quality, and appearance.
- The market for LED fixtures and lamps is, if not in its infancy, certainly preadolescent. There are few standards, few long-term manufacturers, and limited information. Most LED emitters have life ratings that are considerably longer than the age of the product. Producers can enter and exit the market quite quickly, and there’s often little reason to believe that a particular device will still be in production when the first unit fails and has to be replaced. These facts can lead some facility owners to have a level of reluctance to invest in this technology.
Fluorescent technology has had the lion’s share of the commercial lighting market for decades, and pricing and performance have been relatively stable for years. The prevailing industry view is that most of the available improvements and economies of scale have already been realized for fluorescent lighting and few, if any, efficiency enhancements or cost reductions are forthcoming for that technology. The prevailing view of LED technology is that efficiency will improve and costs will go down as market share increases and the technology matures. Typical luminous efficacies for LED luminaires currently range from about 50 to 100 lumens/W, which is comparable to linear fluorescents. Projections for future efficacy run as high as 225 lumens/W. Whether that level of performance is actually achievable remains to be seen.
Lighting power allowances
The allowable lighting power densities of the codes are approximately aligned with one another. Allowable densities are generally reduced from previous versions, but not dramatically, as the code-makers have become concerned about maintaining the quality of the indoor environment at low lighting power levels. Consequently, most of the improvement in buildings’ lighting efficiency will come from enhanced control requirements, rather than lighting power density limits. The prescribed levels are roughly as achievable with fluorescent lighting as with LED, though high-end LED fixtures may provide a bit better headroom.
Interior lighting controls
All of the codes require some form of automatic shut-off for most interior lighting, accomplished with occupancy sensing or with time-based controls. ASHRAE 90.1 and Title 24 require that manual controls be accessible to occupants for all interior lighting. For most spaces, all the codes require a "partial-on" function, limiting the lighting power of the first stage to 50% of the connected lighting power or less. And, all require light-reduction controls that offer at least one control option with substantially reduced lighting power. ASHRAE 90.1 requires a reduction of 30% to 70% while Title 24 and IECC require at least 50% reduction. All of the codes require that light-reduction controls be available to occupants.
Lighting power-reduction controls can be accomplished by dimming all the luminaires, by switching some luminaires off completely, or by selective control of a portion of the lamps in each luminaire. The codes require that the lighting is reasonably uniform when lighting power controls are active.
Lighting power reduction controls provide a slight push toward selection of LED luminaires. For volumetric applications, these controls can generally be implemented with fluorescents by judiciously switching lamps in multilamp fixtures. The uniformity requirement nudges the selection criteria toward LED devices, especially for single lamp fixtures. It’s easy to maintain uniformity by dimming all the fixtures together. The inherent dimming capability of LED fixtures makes them an attractive solution for lighting power controls.
IECC offers a path to compliance that includes a requirement that all fixtures be continuously dimmable, with individual addressability of fixtures where it’s available for the fixture class (C406.4, "Enhanced digital lighting controls"). This path is not strictly required, as it is one of a menu of options for compliance. An across-the-board requirement for continuous dimming will strongly push luminaire selection toward LEDs.
All the codes require automatic daylight-responsive controls in areas where daylighting is available, whether from windows or from skylights. ASHRAE 90.1 requires at least four illumination levels, at roughly full power, two-thirds, one-third, and off. IECC does not specify a power-reduction level, but specifically requires continuous dimming to 15% in offices and classrooms.
Title 24 describes a fairly complex array of requirements, with the number of power-reduction steps required dependent on the technology of the luminaire. For compact fluorescents, only one step of reduction is required, between 30% and 70%. For linear fluorescents, four roughly equally spaced steps are required. Linear fluorescent fixtures that accomplish these steps by switching are required to have at least four lamps per fixture. Title 24 does not mandate that daylight-responsive controls go to full-off.
Title 24’s multistep requirement for linear fluorescents amounts to a nearly de facto requirement for continuous dimming. It is difficult to meet the allowable lighting power densities with four-lamp fixtures while maintaining reasonable uniformity.
ASHRAE 90.1 doesn’t have a requirement for continuous dimming with daylight-responsive controls. IECC has a specific requirement for continuous dimming in specific applications. Title 24 makes continuous dimming all but necessary in daylit areas.
A requirement for continuous dimming favors the selection of LEDs. The low incremental cost of adding continuous dimming to LED fixtures makes them cost-competitive with fluorescent fixtures with more expensive dimming ballasts.
All the codes require daylight-responsive controls in parking structures. ASHRAE 90.1 requires automatic shut-off and motion sensor control that reduces lighting power by at least 30% during periods of inactivity. Title 24 requires daylight-responsive controls but permits any on/off control, continuous dimming, or multilevel controls. IECC doesn’t describe daylighting-control requirements for parking garages.
Title 24 requires controls to reduce total building lighting power by 15%, with reasonable uniformity, in response to a signal calling for reduced power demand. Demand-reduction signals may be sent in response to electricity prices or regional power system emergency conditions. This requirement appears to be unique to Title 24.
The impact this requirement has on the selection of LED fixtures is unclear. The required lighting power reduction is not so large that it can’t be accomplished with fixture or lamp switching while maintaining uniformity, but it’s large enough to present challenges. It’s also unclear exactly how this requirement will be enforced. It may require that 15% of the lighting become merely unavailable during demand reduction. Alternatively, it may require a reduction of the actual real-time lighting demand—a much more stringent requirement with broader implications for fixture selections.
All of the codes require that exterior lighting is shut off by automatic timers or photocells during daylight hours. IECC and ASHRAE 90.1 require that façade and ornamental hardscape lighting be automatically shut off at specific times, as a function of opening and closing times, along with dawn and dusk controls. Title 24 offers several options for façade and ornamental hardscape lighting, including timer-based on/off control and power-reduction controls based on motion sensors or timers.
Remaining outdoor lighting must be controlled to reduce the total lighting power in response to motion sensors. IECC and ASHRAE 90.1 mandate a 30% reduction. Title 24 requires an automatic reduction of at least 40% and not more than 80%. However, the Title 24 requirement for motion sensor control applies only where the luminaire is within 24 feet of the ground. Taller poles are generally widely spaced, and there is concern that current outdoor motion sensor technology can’t reliably operate over broad zones. Title 24 also limits the wattage that may be controlled together to 1500 W, to force the control system to operate luminaires selectively rather than in large blocks.
Time or photocell-based on/off control can be readily accomplished with any of the technologies appropriate for outdoor lighting. Motion sensor controls, however, require a fairly quick response. High-intensity discharge (HID) lamps, the current staple in hardscape lighting, perform poorly in the first 2 to 10 minutes after energization and are not appropriate for control schemes that reduce connect power by turning lamps off. Dimming of HID lamps is possible, but has a number of deleterious effects including reduced lamp life and reduced color performance.
Motion sensor requirements for hardscape lighting tend to drive luminaire selection to LEDs. This is because LEDs provide nearly instant performance and can be operated at less than rated power for extended periods.
Tom Divine is a senior electrical engineer and project manager at Smith Seckman Reid Inc. He is a member of the Consulting-Specifying Engineer editorial advisory board.