How LEDs affect energy codes
Lighting codes and standards are being impacted by the changes and upgrades to LEDs.
For the past few years, the entire lighting industry is experiencing a revolution due to the introduction of LEDs, or light-emitting diodes. With such significant changes in lighting sources, specifiers might expect LEDs also to be impacting the building codes that govern their designs, especially energy codes. Let’s take a closer look at just if and how this is happening in terms of interior lighting.
States around the country usually follow one of two major energy codes: ASHRAE Standard 90.1 or the International Energy Conservation Code (IECC). These codes are interrelated; IECC provides two compliance paths, the first by satisfying specific IECC provisions, or the second by meeting the requirements of the revision of ASHRAE 90.1 in effect at the time of IECC adoption.
While many states adopt one of these codes, other states choose to develop and enforce their own energy code. Because the federal government has adopted ASHRAE 90.1 as the national reference standard, state codes must be at least as stringent as the version of ASHRAE that the Dept. of Energy (DOE) has defined as the effective reference standard (currently this is Standard 90.1-2010). States must certify that their code meets this requirement, and is at least as stringent as ASHRAE 90.1-2010, by Oct. 18, 2013. California’s Title 24 is the most well-known and influential state code. In recent years, many provisions first introduced in the California code have subsequently been adopted by either ASHRAE 90.1 or IECC, such as the “auto on to 50%” requirement discussed below.
Generally, energy codes seek to avoid mandating a specific technology until that technology has been proven to be readily available and meet some level of return on investment criteria. So, while ASHRAE 90.1 and the other codes do not specifically require LEDs, the provisions certainly do influence the lighting sources a specifier might select. And while lighting power densities achieved with LEDs may not always offer significant advantages today over other sources, the lighting industry is banking that the efficacy of LEDs, produced using technologies carried over from the semiconductor industries, will see monumental increases in the future.
All energy codes essentially include provisions for lighting based on two primary circumstances:
- When spaces are unoccupied, general lighting, except for specific areas where safety is of paramount concern, such as stairwells, should be completely off.
- When spaces are occupied, the lighting power density (LPD) energy load should be minimized as much as possible via lighting rules, mandatory controls, and other features to achieve the energy-efficiency goals of the code.
As a result, codes include mandatory lighting rules as well as prescriptive methods to calculate and limit the amount of power that can be used for every building or area type. In ASHRAE, lighting systems and equipment must comply with the general requirements outlined in Section 9.1, the mandatory control provisions in Section 9.4, and the prescriptive requirements of either the Building Area Method (Section 9.5) or the Space-by-Space Method (Section 9.6).
The mandatory control provisions are intended to achieve better energy performance of nonresidential buildings, with a stated goal of achieving net-zero energy by 2030. Even with more efficient lighting sources such as LEDs, the use of controls is recognized as critical to achieving these energy performance objectives.
Let’s look at the foundational ASHRAE 90.1 control requirements and consider how these influence the selection of LEDs.
ASHRAE 90.1-2010 (Section 9.1.2) has a new triggering threshold in which alterations of more than 10% of lighting systems in any building space or exterior area will now be required to comply with the automatic shutoff requirements as well as the LPD requirements. This includes alterations of luminaires as well as replacements of lamps plus ballasts. This is a much lower threshold than previous 90.1 versions, which set the compliance threshold at 50%. For the specifier, this means that even relatively modest lighting upgrades from older lighting technologies to LEDs may trigger this section and invoke compliance with these control requirements.
Another general provision (Section 9.4.1) specifically requires that any automatic control device used to comply with the automatic shutoff, space controls, or primary side-lighted daylighting provisions be either a “manual on” device, meaning that the occupant must turn lighting on manually when entering the space, or lighting can turn on automatically to 50% or less full output (often referred to as “auto on to 50%” or bi-level switching).
ASHRAE Section 184.108.40.206. requires automatic shut-off of general lighting when it’s not needed, by a time clock, occupancy sensor, or other building system signal. Time delays cannot exceed 30 minutes, and the 2010 version greatly expanded the types of spaces in which occupancy sensors are mandatory.
At first glance, this requirement would not seem to promote LEDs as a lighting source, but consider some of the features inherent in LEDs. For instance, LEDs suffer few effects from being frequently switched on or off, unlike fluorescent lamp sources that may experience a decrease in lifecycle if frequently switched, even with programmable start ballasts. Because LEDs do not have this characteristic, designers can reduce occupancy sensor time delays to achieve even greater energy efficiency. A good example of this is the freezer section in a grocery store; LEDs in conjunction with occupancy sensors are often used for freezer case lighting. The sensors turn on the LEDs when someone begins walking down the aisle and turn off lighting shortly after the shopper exits the aisle. In demonstration projects, energy savings have been as high as 80% over conventional lighting sources without controls.
In addition to the well-known automatic shut-off controls, California Title 24-2013 mandates that certain areas (i.e., library aisles, warehouse aisles and open areas, corridors) use controls that turn lighting Partially On or Off automatically during the day when spaces are vacant. Again, while this provision doesn’t specifically require LEDs in these areas, dimmable LEDs are a design choice that could easily be integrated without some of the energy efficiency trade-offs that might occur with fluorescent dimming, for instance, which does not provide a 1:1 energy reduction for dimmed light levels.
ASHRAE Section 220.127.116.11 mandates the inclusion of a control device accessible to occupants so they can turn lighting on, off, or adjust light levels when desired. The device must be capable of reducing light levels with at least one control step between 30% and 70% (inclusive) of full lighting power in addition to all off. Again, the flexibility of LEDs for multi-level control would be a significant factor in the design process.
California has taken this multi-level control requirement even further. In Title 24-2013 (Section 130.1(b)), for rooms over 100 sq ft with greater than 0.5 W/sq ft LPD (some other exemptions apply), this multilevel requirement now mandates different lighting power levels based on the type of lighting installed. For fluorescent lamps greater than 13 W, in addition to “full on” and “full off,” three other levels are required: a low level (20% to 40%), a medium level (50% to 70%), and a high level (80% to 85%). While this can be done with other methods, many recognize that the most logical way to meet this requirement is to use continuous dimming ballasts. Interestingly, Title 24-2013 does not require multiple levels when LEDs are used for general lighting in rooms over a certain size and lighting power density. In this situation, the fixtures must be capable of continuous dimming from at least 10% to 100% power level.
Daylighting is another area where LEDs come into play. ASHRAE 90.1 (Section 18.104.22.168) has extensive requirements for automatic daylighting control in side-lit and top-lit areas; one key requirement is the capability of multiple light level reductions (at least one control step between 50% and 70% full output and another step no greater than 35% of design power). In Title 24-2013 (Section 130.1(d)), mandatory daylighting requirements will be required when the total lighting power in primary side-lit and sky-lit daylight zones is greater than 120 W.
Using lower-power LED fixtures could eliminate the need for daylighting controls if the LEDs prevent this wattage threshold from being crossed. As noted already, since LEDs offer the benefit of being easily dimmed, this may well drive the use of LED lighting sources in new construction that must comply with all the code requirements. Continuous dimming is a much less obtrusive interaction for the occupant in the space than having lighting turn completely on and off when daylight levels change in the space.
Another new requirement is that of commissioning the lighting and control system. ASHRAE Section 9.4.4 requires lighting control devices and systems be tested to ensure that control hardware and software are calibrated, adjusted, programmed, and in proper working condition in accordance with construction documents and the manufacturer’s installation instructions. This includes confirming correct placement, sensitivity, and time-out adjustments for occupancy sensors; correct programming for programmable switches or panels; and correct light level reductions by photosensors.
This functional testing and certification must be performed by a party identified in the construction documents that is not directly involved in either project design or construction. While LED fixtures currently are designed to connect to the same power circuits as other fixtures, the new technology can lead to surprises for anyone commissioning the systems—for instance, every dimmer that controls an LED fixture must be verified to be the correct type (e.g., 0 to 10 V, forward phase, reverse phase, etc.) because there is no single standard for dimming LEDs. Questions may also arise because a dimmer capable of handling a small incandescent load may not be able to handle the same load when controlling LEDs due to the LEDs’ driver circuitry.
LEDs will also find application in some of the most innovative requirements. For instance, California Title 24 introduced demand response requirements in the 2008 revision (Section 131(g)) that applied to retailers over 50,000 sq ft. This is expanded in the 2013 version to apply to any building or tenant improvement of over 10,000 sq ft (Section 130.1(e)). For applicable buildings, total lighting power shall be capable of being automatically reduced by a demand response (DR) signal by at least 15%. While the DR requirement has not yet been included in ASHRAE, it’s likely to be included in some future revision.
Energy codes continue to evolve toward driving more energy-efficient lighting performance, both by encouraging selection of more efficient lighting sources and by mandating the use of controls to minimize or eliminate unnecessary lighting energy consumption. As LEDs capture a greater percentage of the general lighting fixture market, energy codes will no doubt continue to adopt lower lighting power densities and mandatory control requirements that take into account the beneficial properties of LEDs, which in turn will help further increase their adoption.
Charles Knuffke is the Western vice president at WattStopper and is a member of the Illuminating Engineering Society. With more than 25 years of experience in lighting controls, he has extensive experience in code development, particularly with the California Energy Commission on California Title 24, and has given many educational presentations on energy code topics.