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 18.104.22.168. 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.