LED Lighting for Commercial Ceilings

New panel products and technology provide high-quality, efficient light

Peter J. Arsenault, FAIA, NCARB, LEED AP

Providing commercial buildings with good-quality interior lighting has become as much a science as an art. The need for greater energy efficiency mandated by codes, standards, and professional best practices has spurred improvements to existing lighting technologies and given rise to entirely new ones. Fluorescent light fixtures, for example, have been a long-standing staple for commercial lighting and have undergone many improvements in their lamps, ballasts, and fixture design, resulting in more light output from less energy. Meanwhile, new technologies using electronic light-emitting diodes (LEDs) have emerged, been developed, and brought to market in a variety of ways. Among the newest available technologies are luminous LED panels that provide even greater efficiency along with other attributes that make them worthy for consideration in all commercial building designs. These LED panel fixtures can meet and/or exceed energy conservation requirements while also addressing the quality of the luminous environment appropriate to the design intent of the building.

Lighting Performance Overview

In order to put the energy and light-emitting performance of these different lighting technologies into perspective, let's start with a review of some fundamental lighting principles. Since we are talking about electrical energy that powers all of these lights, the energy that is consumed is measured in watts, or more commonly kilowatts (1,000 watts). The electrical utility company charges not just for the wattage but also for the time that energy is being consumed and hence the common billing unit of kilowatt-hours (kWh). Based on this, it should be clear that electrical energy consumed for lighting is a function of both the amount of watts that each light fixture requires to operate and the time that the lights are on. In other words, the total kWh needed for lighting a commercial building on any given day is equal to the electrical power (kilowatts) consumed by the light fixtures multiplied by the time (hours) those fixtures are turned on.

LED panel lighting takes advantage of the latest energy-efficient technology while producing very high-quality light for commercial spaces. Photo courtesy of RAB Lighting, Inc.

The time portion of this equation is obviously governed by a whole series of variables. The building location, usage, daylighting options, management policies, and most notably, human input all can work to positively optimize or negatively maximize the amount of time that the lights are on. Energy codes address this variable by calling for automatic means to turn off lights when spaces are not occupied or when the building is closed, with security and safety lighting given due consideration. The ability to turn off or dim down electrical lighting systems when not needed is recognized as a key contributor to minimizing environmental impact. While lighting controls are an important topic due to the impact they can have on overall energy use, we will focus here primarily on the energy needed (watts) for commercial lighting and leave controls for another article.

Electricity use for lighting is a function of both power consumed (kilowatts) and time (hours) that the lights are on. Image courtesy of RAB Lighting, Inc.

Most commercial lighting fixtures have several parts, all of which contribute to the ultimate total energy consumption discussed as follows:

Lamp or Light Source

The primary power consumption in commercial light fixtures is the light source commonly referred to as a bulb or lamp. There are four common types of lamps used in commercial buildings, namely incandescent/halogen lamps, fluorescent lamps, HID lamps, and LED lamps.

• Incandescent and halogen lamps: Dating back to the early 1900s, these lamps employ the oldest basic technology in use today for lighting. These lamps are sometimes used for highlighting or spot-lighting particular areas in commercial areas. Pressed glass aluminized reflector (PAR) lamps are an example of this type that can use either a tungsten incandescent filament or a tungsten halogen combination that creates a longer-lasting, brighter light. Hence, their respective abbreviated common names of incandescent or halogen lamp.

• Fluorescent lamps: Fluorescent lamps were first introduced in 1939 and have gained great popularity in commercial buildings ever since. They create light when an electric arc passes through inert gas and mercury contained in a glass tube that is coated with phosphor on the inside. The tubes are available in a variety of shapes and sizes, including the common 4-foot and 8-foot linear lamps, U-shaped, and round. In contrast to these fluorescent lamps, compact fluorescent lamps (CFL) were introduced in the 1980s in a form that offered a new range of compact shapes with dictated socketing or screws—in bases like a traditional incandescent bulb.

• High-intensity discharge (HID) lamps: Originally referred to as mercury lamps in the 1930s, they were trumped in the 1960s by metal halide and high-pressure sodium (HPS) technology. In each case, the glass enclosure is under pressure with an electric arc used to create a very bright point source of light that can, with the help of a reflector, project a far distance, making them well suited for high ceilings. This process of producing light requires some time to both start up and cool down, however.

• Light-emitting diodes (LEDs): Unlike all of the other lamps described, an LED uses a solid-state semiconductor to convert electrons (electrical energy) directly into photons (light). This means that an LED uses no heavy metals like mercury or lead, uses no gas, and needs no filament to operate. Because of its electronic nature, there are no moving parts that can fail and it does not require a fragile glass bulb. Colored LEDs became common in the 1960s and '70s and were used in electronic devices such as watches and calculators. By the 1990s they were being used in exit signs and traffic lights as clear LEDs became available and their brightness increased. Currently LEDs are available in a full range of colors and can be clustered together in bulbs or fixtures to create a complete light source.

Light-emitting diodes (LEDs) are a low-energy, high-output light source that work by using solid-state electronics to change electricity into light. Photo courtesy of RAB Lighting, Inc.

In addition to the differences in the development and physical characteristics of each of these lamps, there is also a notable difference in the amount of energy that each one requires to produce equivalent amounts of light. The unit of measurement that describes the quantity of light emitted from a source of light is called a lumen. Different lamps are usually compared based on the amount of lumens of light that they produce for each watt of electricity they consume. This measure of lumens per watt (lm/W) is the lamp's “efficacy” (sometimes incorrectly called efficiency) and is similar to a “miles per gallon” rating for cars. The higher the rating, the more output that is achieved (e.g. light or miles) compared to the energy put in (e.g. electricity or gasoline). It should be noted that just as an older car may get worse gas mileage, the lumen output of most lamps drops off over time by as much as 20 to 30 percent for incandescent and fluorescent lamps.

Looking at the four categories of lamps, incandescent and halogen receive the lowest efficacy, meaning they need a lot of energy to produce their light output. This is in part due to the fact that up to 90 percent of the electricity gets turned into heat rather than light. Fluorescent lamps are notably cooler and perform much better, particularly with advances made in the past decade such that a common 40-watt linear tube now usually only requires 28 or 32 lamp watts to produce the same lumen output. HID lamps typically produce a great deal of light, so their lm/W rating is usually favorable, but they aren't always appropriate choices in many locations due to poor color rendering and lack of beam control without a reflector. LED lamps are known for their low energy needs, good color rendering, precise beam control, being cool to the touch, and most importantly, their efficacy is commonly superior to the other lamp types.

One other characteristic of different lamp types is their average rated life. Manufacturers will test representative lamps and determine how many hours they will continue to work until they “burn out” or no longer provide light. The average is computed based on this testing and the manufacturers can indicate a rating of their average life expectancy. Incandescent and halogen lamps are often rated for approximately 1,000 to 2,500 hours. Fluorescent and HID lamps are rated from 6,000 to 24,000 hours, meaning in an average commercial facility with the lights on 10 hours a day, they could last anywhere from 2 to 6 years before needing to be replaced, assuming that their light quality and efficacy remain high. However, modern fluorescent lamps, such as T5, T8, and T12 versions, all have significant lumen depreciation over time.

LEDs clearly lead the way in terms of average rated life. They are rated between 50,000 and 100,000 hours, meaning that they could easily operate effectively between 12 to 27 years. This rating is based not on the LED lamps “burning out” but rather losing light output to the point that it is perceptible to people. L70 is an industry standard to express the useful lifespan of an LED. It indicates the number of hours before light output drops to 70 percent of initial output. Hence their long average rated life is based on the average number of hours (years) that it will take to reach this 70 percent light reduction. With that type of longevity and lumen maintenance, there is no need to store spare lamps or to replace them, thus freeing up maintenance budgets and storage costs.

Lamp Ballasts and Drivers

Since fluorescent and HID lamps require a controlled arc of electricity to create light, a ballast is used to control and limit the flow of electricity during start up and operation. Without them, large amounts of electricity would flow in to create the arc in an unrestricted way.

There are two types of ballasts that are commonly used. Electromagnetic ballasts were the original type used when fluorescent lights were first made available. These ballasts are essentially an electrical transformer with a steel core that is wrapped with wire and placed in a metal housing. These components work together to choke or limit the amount of current that goes into the lamp. In the process, they also produce unwanted heat and noise so they are commonly wrapped in asphalt to conduct the heat away, reduce noise, and help improve longevity.

The second and more common type used today is an electronic ballast. In this case, solid-state circuitry is relied upon to dampen and control the flow of electricity to the lamp. Electronic ballasts allow the electrical current to flow at a much higher frequency (20,000 Hz for electronic vs. 120 Hz for magnetic ballasts), reducing any audible noise while also operating at cooler temperatures. Although they are commonly more expensive than electromagnetic ballasts, they are more efficient and more flexible such that the overall benefits are worth the small additional cost. In fact, it is safe to say that almost all new light fixtures are produced with electronic ballasts except for some that need a heavy-duty or temperature-tolerant ballast based on their location.

A comparison of the rated lifespan of different lamp types based on 10-hour-per-day operation. Source: RAB Lighting, Inc.

Ballasts can allow fluorescent lights to be dimmed, although the percent of dimming will depend on the type of ballast. Electronic ballasts can readily dim lamps down to 10 percent, 5 percent, and even 1 percent of full light output while electromagnetic ballasts generally are limited to 50 percent dimming. As the fluorescent lamps are dimmed down, they use less energy, making them particularly useful in situations where daylighting is designed into a space and photo-sensors trigger the dimming process.

From an energy standpoint, not all ballasts are created equal. Since they are located in the flow of electricity, they use and consume some energy in the process of conditioning it. Electronic ballasts are more efficient and consume less energy than the electromagnetic type, causing energy codes to favor them as a result. Recognizing this consumption, ballasts are tested and rated to determine the ballast factor (BF), which is simply the percentage of a lamp's rated lumen output that can be expected when it is operated on a specific ballast. So, for example, a ballast with a BF rating of 0.90 results in the lamp emitting 90 percent of its rated lumen output. Since the ballast is part of the overall lighting system with component parts that work together, this light reduction obviously plays into the overall lighting of the room or space in the building.

LED lighting does not require ballasts—relying instead on an electronic driver to condition and control the electricity. The driver uses a negligible amount of electricity to operate, making it much more efficient than ballasts. Drivers are rated for overall power factor similar to rating ballasts; however since drivers use so little energy, their power factors are commonly over 99 percent. LED lights are also dimmable, using dimmable drivers which allow the amount of light and energy to be reduced electronically.

A driver for an LED fixture is a small thin unit that can be mounted to an LED light fixture. The red portion shown next to the driver is a back-up battery option for emergency lighting. Photo courtesy of RAB Lighting, Inc.

Luminaires

A completely packaged light fixture including lamps, holders, internal controls, reflectors, housings, ballasts and/or drivers is referred to as a luminaire. In essence, it is a manufactured electrical device to produce, control, and distribute light. The design and physical attributes of the luminaire are the final influencing factor on the total light that is emitted. The efficacy of light sources, the ballast factor, and the efficiency of the luminaire design all combine to determine the luminaire efficacy rating (LER) for fluorescent fixtures or the ultimate lm/W (lumens per watt) for LED lighting fixtures. LER is different from, and advantageous to, traditional lamp efficacy measurements because it takes into account all components of the luminaire system: luminaire efficiency, ballast factor, and input wattage.

The National Electrical Manufacturers Association (NEMA) has taken on the task of defining the tests and standards for determining the LER for fluorescent lighting fixtures in NEMA Standards Publication LE5-2001: Procedure for Determining Luminaire Efficacy Ratings for Fluorescent Luminaires. In this publication, they identify categories of lamps, ballasts, and fixtures that can be combined to create different luminaires. The procedures for testing and reporting are detailed so that equal comparisons can be made between different luminaires. They point out that LER values are published based on manufacturers' literature and are based on a specific lamp used in conjunction with a specific ballast in a particular luminaire. Since there are many variables between ballast and lamp performance, use of the LER data to compare different luminaire products requires attention to any differences in ballasts and lamps used in the tests. In this way, the focus of the comparison can be on the differences in fixture design and the optical properties that enhance or restrict light from leaving the fixture. The goal is obviously to get the most light out of the fixture for the least amount of watts. Hence a higher rather than a lower LER value is desired for fluorescent luminaires since it reflects the total lumens output compared to the watts input.

LED luminaires for commercial space applications are currently available that compare very favorably to fluorescent luminaires since they can provide equivalent light output using about half of the energy. The U.S. Department of Energy's Solid State 2011 index lists LED luminaires performing in the impressive range of 40-50 lm/W. The tests for this determination are more straightforward since there are fewer components to address. Hence, it is based on a straight lumens output compared to the total watts input for the lamps and driver.

Lighting Power Density

Energy codes, standards, and green building rating systems have taken all of this lighting efficiency information and applied it to buildings on a square footage basis. The common term of lighting power density (LPD) is a measure of the number of watts required per square foot of lighted area. Depending on the type of use in a building, the codes set a maximum number of watts that are allowed per square foot to be compliant. So, for example, low light areas such as parking garages and warehouses are allowed 0.3 and 0.8 watts per square foot respectively. Spaces that need higher light levels such as theaters and libraries can go to 1.6 and 1.3 watts per square foot respectively. In between is where many other commercial spaces fall such as offices, exercise centers, hotels, etc. which are allowed 1.0 watts per square foot. So for a typical office building, a 1,000-square-foot office area is allowed to consume 1,000 total watts for lighting.

Showing compliance with the LPD includes accounting for the energy used in the entire luminaire. Hence the LER or lm/W need to be shown based on published data for the lighting fixtures being used or specified. That means the ballast factor and luminaire design is accounted for in the LPD. So a 2 x 4 lay-in fluorescent luminaire with two lamps and a ballast may require 72 watts to power two 34-watt lamps and an electronic ballast. That will limit the total number of fixtures in a 1,000-square-foot office area to about 13 luminaires. Since LED lighting fixtures have inherently lower energy consumption as compared to an installed fluorescent lighting fixture, a comparable 2 x 4 lay-in LED luminaire could require as little as 44 watts to operate in total. That means as many as 22 LED luminaires are allowable in the same 1,000-square-foot office area. If that many aren't required, then the energy reduction increases by using fewer fixtures, reducing the actual LPD and saving the owner money on electrical lighting costs.

Light color can be a rather subjective thing to discern between different people, but standardized measurements and tests help determine generally accepted light quality characteristics. Image courtesy of RAB Lighting, Inc. Color rendering index (CRI): The CRI is a number between 1 and 100 used to describe the ability of a lamp to accurately render within the lighted space all the colors in the visible spectrum. For example, a CRI of 80 or above normally indicates that the lamp or luminaire has good color properties such that it would not significantly distort or diminish the true color of an object being illuminated. A low CRI rating would tend to distort the color of illuminated objects, making them appear too yellow or blue for example. Color temperature: The color temperature of a light source is a determination of its color appearance. Color temperature is used to describe the overall color tone of a white light source such as warm in appearance or cool in appearance. Correlated color temperature (CCT): The CCT numerically describes the overall color appearance of a lamp measured in degrees K or Kelvins. Common warmer light sources, similar to incandescent color, have a Kelvin temperature in the range of 2,700K to 3,000K. Somewhat cooler or neutral light sources commonly used in offices can range between 3,500K and 4,100K. Very cool color temperatures, often used to match daylight, are between 5,000K and 6,500K.

 

Light Quality Considerations

Energy savings are great particularly when determining the quantity of light needed, but what about the quality of the light desired for a building? Good lighting design begins with the development of a thoughtful statement of design intent for the various spaces within a commercial building project. This design intent obviously needs to be coordinated with everyone on the project team such as architects, interior designers, lighting designers, engineers, etc.

Establishing light levels and lighting quality to match the design intent should be based on professional consensus standards such as ANSI standards and recommendations published by the Illuminating Engineering Society of North America (IES). Most of these standards have been developed in the context of meeting or exceeding current energy code requirements such as the International Energy Conservation Code (IECC) or ASHRAE/IES 90.1. These standards are based on the premise that more light is not necessarily better light; rather it is all about the characteristics of that light. Is the light focused or dispersed? Is it used to create contrasts or uniformity? Are there a mix of lighting needs within a space such as ambient lighting and task lighting that need to be addressed? What effects related to the color of the light are desired?

Color in particular is an important and controllable aspect of electrical lighting. Although perceptions of color can vary between different people, the IES describes several key metrics that are used to define color traits when applied to lighting. These include a color rendering index (CRI), color temperature, and the correlated color temperature.

Once the fundamental questions of preferred color and other light qualities are answered it is then a matter of determining the best lighting strategies to help achieve the stated design intent. Some strategies are related to the building such as using light colored finishes which need less light than dark colored finishes. Similarly, open spaces, interior glass, and low partitions allow for artificial light to flow from one area to another and could reduce the number of luminaires required. Other strategies have to do with the use of daylighting in the building and how to coordinate electric lights and controls with daylighting zones in a building.

One important consideration in all lighting designs is glare. Light sources that are too focused or too numerous will create the condition of too much light (excessive luminance) causing most people to have a negative response from visual discomfort to the point where they will squint or look away. It also detracts from our ability to see detail accurately to the point that some people will try to thwart the excess light by covering or shading it thus causing potentially unintentional consequences, not the least of which is wasted energy. The other aspect of glare is too much contrast. If our eyes are adjusted to a certain light level and a light source is introduced of a notably higher light level, then we have the same negative reaction. Hence, the preferred situation in most commercial building settings is to achieve a uniformity of lighting across a particular space. However, using a combination of lower level ambient lighting with a higher level of localized task lighting has been done quite effectively without producing glare. This can be a particularly helpful strategy for spaces that have a lot of computer screens since it can eliminate reflections on the screen which make them difficult to read.

LED Panel Luminaire Attributes

As we have seen, LED luminaires use electronic light-emitting diodes to produce light very efficiently. In fact, they could well be the most efficient and cost-effective choice for many commercial buildings. One type in particular, an LED panel luminaire is a complete solution that provides both appropriately ample light quantity and excellent light quality as well. Some of the attributes of this type of luminaire are as follows.

Physical Attributes

An LED panel fixture is fundamentally different than a fluorescent troffer fixture. Instead of separate housings, lamps and diffusers, the LED panel is a complete, one-piece box style enclosed product. To provide the greatest flexibility, LED panel luminaires are manufactured to be installed into suspended ceilings as drop in troffer style fixtures. Through the use of trim kits, they can also be flush mounted to gypsum board or plaster ceilings. As such, they can be easily incorporated into new or existing ceiling designs with relative ease.

LED panels are commonly shaped to match industry standard commercial fluorescent luminaire sizes including 2x4, 2x2, and 1x4 with a nominal depth of only 3 inches. The driver is located outside of the main optical chamber of the panel for cooler operation and service access when required. This driver location has minimal impact to fixture depth. For luminaires that need to serve as emergency lighting, a battery backup can be fitted to match the depth of the driver in some cases and maintain clearance around the panel fixture.

In terms of operation, LED panel fixtures exhibit all of the desirable attributes of LED lamps. The light appears instantly without any waiting or delay when the luminaire is switched on. They are completely dimmable using approved, tested dimmers and dimming drivers designed for LED use. In these cases, they have been found to perform without any flickering that sometimes occurs with dimmed fluorescent lamps. They can also be step dimmed to customize light output as needed. There is also the possibility of zone control and integration into a Building Management System (BMS) to address variable use conditions, energy consumption control, and daylight integration so as to maintain light quality for the building space.

LED panel luminaires are available in a range of industry standard sizes for commercial ceilings including 1x4, 2x2, and 2x4. Image courtesy of RAB Lighting, Inc.

One other significant physical attribute is the fact that LED panels do not exhibit the temperature sensitivity that fluorescent luminaires can, particularly in colder settings. This makes them equally well suited for unheated parking garages and industrial settings as for offices and other temperature controlled commercial spaces.

Longevity Attributes

The long life of LED lamps applies to LED panel luminaires as well. An average rated life projection of between 50,000 and 100,000 hours to the L70 point means that LED panels could be installed once and not need to be replaced for decades. Key to this longevity is the fact that the electronic make-up of the LEDs allows the lumen output to remain constant over time, only decreasing slightly towards the end of its rated lifetime. Once its service time is complete, the luminaire can be removed and recycled then replaced with a new one at that time.

Light Quality Attributes

First and foremost, LED panel luminaires can now be manufactured to produce excellent color quality. Just as significantly, the shade of white light appears clear and consistent over time, unlike HIDs or other lamps that can change in color. And adding a dimmer doesn't detract from the quality since dimming LED panels can provide uniform appearance without changing color.

In order to produce this high level of color consistency, LED manufacturers have developed a systematic manner to address the normal variations inherent in any manufactured products. As LEDs are produced they are evaluated and sorted for variations in brightness (lumens). Then, using a sophisticated tool known as the four-step MacAdam ellipse the LEDs are evaluated for their specific color or chromaticity based on the range of visible light colors. Each LED is sorted or “binned” together with other LEDs to create an overall uniformity of light appearance in the panel luminaire. Unlike traditional lighting design, LEDs can be mixed by color and can help the panels, which use multiple LEDs, take the best advantage of LED color performance. This LED color mixing is an effective technique to achieve consistent, repeatable, multi-LED luminaires. Color mixing also allows the use of a large chromaticity range while reducing LED unit costs. This creates a high CRI rating with a fuller light spectrum which is generally rated better than a limited spectrum for interior spaces. Ultimately, this binning and mixing process allows for an appropriate CCT to be derived and produced.

Overall, the light quality of LED panel luminaires has come a long way since early LEDs used in electronics. With higher light outputs, more precise control over coloring, and the ability to spread the light out evenly from a luminaire, they possess the ability to provide better interior lighting quality than other traditional lighting types.

Specifying LED Panel Lighting

When specifying LED panel luminaires, there are choices and specification details to pay attention to so that the right lighting is produced for the location where they will be installed. The Master Format section number commonly used is in the 26 50 00 series for Lighting and specifically in 26 51 13 for Interior Lighting Fixtures. (Corresponding Omni Class Codes and UniFormat II codes if used should be verified by the specifier). Some of the relevant items to address in a standard three-part specification format are highlighted as follows.

Part 1 General

Specifying panel LED luminaires for quality control is a matter of referencing testing standards. In addition to common Underwriters Laboratory (UL) ratings for dry or damp locations, IES recommendation and practices described in the current versions of standards LM80, LM79, TM21 for lighting fixtures are appropriate. These tests indicate the longevity of the tested LEDs used in the product among other things. Note that the photometric reports from these reports represent absolute photometry in this case not relative photometry as for other types of lighting fixtures. Note also that additional IES TM standards are currently under development in an effort to better define LED luminaire performance characteristics and may be available soon to reference as well.

Submittals requested for LED panels should be the same as any other luminaire including manufacturer's product information and lighting output information. Obviously this information is needed during the design process as well in order to create the ceiling lighting plan, but during the construction phase the submittals should be used to assure that the luminaires designed around and specified are the ones ordered for installation. This will help with checking final coordination with the specific ceiling type being installed and integration with other project requirements such as green building and energy performance criteria. It is also appropriate to request a full warranty on the LED panels with a minimum 5-year warranty on all aspects of the luminaire available from manufacturers.

Part 2 Products

As with all products, there are a number of options and choices for specifying LED panel luminaires. Some of them are listed as follows:

• Size: Standard ceiling fixture sizes are available and should be selected as 2x2, 2x4, or 1x4 luminaires with location sizes shown on ceiling plans.

• Mounting: Recessed or surface mount luminaires need to be specified or indicated in a lighting schedule if both are used.

• LEDs: Commonly the LEDs used in the luminaire should be specified as long-life (50,000, 75,000 or 100,000 hours). They should also be binned using a 3-step MacAdam Ellipse process and mixed to provide uniform light output and color across multiple fixtures.

• Light color: LED panels can generally be specified with a CCT of 3,000K (warm), 3,500K (warm neutral) or 4,000K (neutral) and a CRI of 82 – 85 depending on the CCT selected.

• Driver: Constant current drivers with power factors at 99.6 percent for both 120 and 277 V systems are available. If dimming is required, then the driver should be specified to dim from 10 to 100 percent.

Different LED light panel sizes and lumen outputs will require different electrical wattages as compared in this chart. Chart courtesy of RAB Lighting, Inc.

• Wattage/light output: The total wattage of an LED panel luminaire will vary based primarily on the fixture size and the desired light output levels specified. Color choice and the addition of a dimmer will also impact wattage, but to a lesser extent. For example 1x4 and 2x2 LED panels may require 34, 41 or 52 watts for the entire luminaire depending on choices made while a larger 2x4 model can require only slightly more power at 44 or 59 watts. Light output will vary based on the selections made between 75 to 110 lumens per watt (lm/W). Manufacturers' data should be consulted to be sure that wattage and light output are properly understood and specified.

• Luminaire lens: The lens is usually integral to the luminaire and can be specified as high-transmission acrylic with excellent light distribution and uniformity.

• Housing: Lightweight extruded aluminum is commonly used for the housing to help with durability and controlling the weight of the luminaire.

• Finishes: Like most commercial ceiling luminaires, the common finish is matte white and can be specified without VOCs or any toxic heavy metals.

Since some aspects of products vary between manufacturers, using the component specifications above will aid in product to product comparisons during design and assure appropriate installations during construction.

Part 3 Execution

Providing and installing LED panel luminaires is also similar to other luminaires.

• Examination and preparation: The ceiling needs to be ready to receive the luminaires and the wiring runs need to be installed which all speak to proper project coordination during construction. If integration into a larger building management system or lighting control system is part of the project, then that coordination needs to be done ahead of time as appropriate.

• Installation: Typically, installation is intentionally straightforward following manufacturer's installation instructions and electric code requirements.

• Cleaning and protection: Since these are light-emitting panels, the cleanliness during construction and installation is important. Removing dirt, fingerprints, etc. can commonly be done with a non-abrasive cleaner.

• Punch list and final inspection: All LED panels should be turned on and off to demonstrate that they work properly including any dimming functions. Light color should also be readily observable for consistency per the specifications.

• Post occupancy: Many green building and sustainability programs look for information following installation for evaluation and validation of the design intent from both an energy usage and environmental quality standpoint. If required, this should be referenced in terms of how the lighting plays into that post-occupancy evaluation and monitoring.

Conclusion

Compared to other lighting choices, LED panel luminaires provide an easy means to dramatically reduce energy consumption in commercial building spaces on the order of 31 to 64 percent. At the same time, the light quality can be specified to meet a range of needs but is generally regarded as very high overall delivering very good light color choices through a unique binning and mixing process. That means that any LED color variation between fixtures is imperceptible to the human eye. When installed in commercial buildings, LED panels can provide smooth and uniform light from edge-to-edge for a clean, modern look when recessed in suspended ceilings or surface mounted to other ceilings. In addition to energy cost savings, their very long service life saves notably on maintenance and lamp replacement costs. And with utility rebates available up to $100 per fixture, they are even more cost effective when included in new or existing building projects. All of these attractive and desirable attributes have allowed this LED panel technology to be among the fastest growing luminaire types available today. They should clearly be considered for current and future commercial projects.

Peter J. Arsenault, FAIA, NCARB, LEED AP, is a nationally known architect, sustainability consultant, technical writer, and continuing education presenter. www.linkedin.com/in/pjaarch

RAB Lighting is committed to creating high-quality, affordable, well-designed, energy-efficient LED lighting and controls that make it easy for distributors to sell, electricians to install, and end-users to save energy. RAB’s LPANEL™ delivers ultra smooth edge-to-edge light in a modern design and breaks new ground in efficiency, delivering up to 106 lm/W. Request a free sample of the 2x2 panel and see for yourself. www.RABLED.com