Selecting the Right Architectural Lighting Fixture for Any Project Space  

Fixtures, referred to as luminaires within the lighting profession, are available in many different sizes, wattages, lamp types, lighting distributions and appearances. Selecting the right lighting for a project is critical to protecting the daily functionality, ambience, and operating economics of a space. The correct combination of lighting fixtures and lamp types will provide the necessary amount of light, where it is needed, when it is needed, and creates the special character of the space in the most energy efficient way possible.

To begin finding the lighting fixtures and lamps that will best fit a particular project, the design team must first define the functional and aesthetic goals for the space. Describing the visual tasks that will be performed in the space, such as reading, using computers, or examining merchandise, and how people in the space should feel, cozy, energetic or focused, will outline the foundational goals for the final lighting plan. Once a decision is made on the specific purpose for the space and the particular characteristics the space should possess, the design team will start exploring the lighting fixtures capable of delivering the right light for the project.

Non-Directional Lighting Fixtures vs. Directional Lighting Fixtures

At the most basic level, the lighting needed in a space can be divided into three groups: general lighting (also referred to as ambient lighting), accent lighting and task lighting. General lighting refers to lighting that is intended to provide illumination for general, non-specific use of the space. General lighting should enable a person to move freely and comfortably around the space, feeling safe and secure. Accent lighting adds drama and dimension to a room by creating points of visual interest. Accent lights are used to draw the eye to paintings and sculptures or highlight a textured wall or other interior design element. Task lighting is designed to provide the appropriate amount of illumination to support specific tasks that will be performed in the space, such as reading, working on a computer, eating or showcasing new merchandise.

Selecting the right fixture for a project space or signage is critical to ensuring the proper functionality, ambience, and operating economics day after day. Photo courtesy of Bock Lighting

While general lighting needs can be met by lighting fixtures that cast illumination in a broad and universal footprint (non-directional), accent and task lighting often require lighting fixtures to be capable of focusing their illumination in a specific direction. These directional lighting fixtures can target items or surfaces needing emphasis.

Beyond providing targeted task or accent lighting, directional lighting fixtures can reduce the energy consumption of a space in two ways. First, directional lights can be kept OFF when the room is not in use or when the light-intensive task is not being performed, without impacting the functionality and ambient light levels of the larger space. Secondly, directional lights are typically closer to the object they are illuminating than a general lighting fixture and that proximity may require less overall wattage to provide the desired level of illumination on the surface. However, it should be noted, that if directional lighting is not turned OFF when unnecessary, it has the potential to create greater energy waste due to the increase in fixtures.

Instead of relying on only non-directional lighting or only directional lighting in a room, a good balance is often the best solution. Where spaces with only general lighting may not provide enough illumination on a specific surface to support a more visually challenging task and cannot highlight specific areas of interest, spaces equipped with only directional task or accent lighting, with no general overhead illumination, may appear darker than a space with general lighting and create a space with such stark visual contrast, between the dark ceiling and the directional lighting, that it may cause physical discomfort and eye strain for people in the space.

Overview of Architectural Lighting Fixtures

Lighting devices that are mounted to the structure of the building are considered architectural lighting fixtures. Lamps and other moveable lighting devices that plug into outlets are referred to as portable lighting. There are eight types of architectural lighting fixtures commonly used in commercial and institutional projects.

Some architectural lighting fixtures are best suited for providing either general or task/accent lighting, while some fixture types can provide both.
Architectural Fixture Type	General/Ambient Lighting	Task/Accent Lighting
Surface-mounted, hanging, recessed luminaires (troffers)	X
Track Lighting	X	X
Cove Lighting	X	X
Downlights	X	X
Reflector Lamp		X
Sconces	X
Wall Wash		X
Chandelier	X

 

Surface-mounted, hanging, and recessed luminaires typically fitted with fluorescent lamps are commonly used to provide general or ambient lighting for the general use areas in offices and other large commercial and institutional facilities. This type of fixture, regardless of mounting type, is often referred to as a troffer, which received its name because it literally resembles an inverted trough that serves as a support and reflector for the lamp. These fixtures can deliver predictable levels of consistent light throughout a space.

Track lighting refers to an electrical track that is mounted on the ceiling and fitted with adjustable lighting units, for general or directional lighting, that can be easily re-positioned along the track. These systems are particularly useful for display and gallery lighting.

Cove lighting fixtures are designed to fit into a cove or pocket that is built into the ceiling or wall in the space. These fixtures provide indirect light, bouncing light off of the ceiling and into the larger space, while remaining concealed from view. These fixtures can be used to provide general ambient lighting or to highlight areas of architectural interest in the built environment.

Downlights are among the most widely used architectural lighting devices. As their name implies, these fixtures emit light in a straight downward direction. These fixtures are available in a variety of shapes, sizes, and lamp types and can be used to provide general use lighting or directional lighting to illuminate a horizontal plane. Downlights can be recessed, surface-mounted, or hung on a stem.

Fixtures with reflectors can be suspended from the ceiling or attached to the wall with a gooseneck pipe bracket (shown here). Photo courtesy of Bock Lighting

 

Fixtures with reflectors employ an opaque reflector that directs light from the lamp in one direction. They can be suspended from the ceiling, as a directional pendant light, or attached to the wall with a gooseneck pipe bracket, as a directional wall-mount lighting fixture. Many have swivel mountings that provide easy adjustability for flexible display lighting.

Sconces are lighting fixtures that most often provide uplight, but can provide downlight as well, and can be employed in both decorative and functional capacities. Sconces are commonly wall-mounted and have been used to provide the ambient light for long corridors.

A wall wash is a fixture that directs light from the ceiling to an adjacent wall to highlight vertical surfaces. It can be used as a decorative lighting element to emphasize the texture of a wall.

Chandeliers are widely used as decorative fixtures that provide general light. They can direct their light up, down, or both.

Predicting the Performance of a Fixture in a Space Using Photometric Test Reports

It is not enough to approve a fixture for a project based on fixture appearance, craftsmanship, mounting type, and cost. Design teams also want to know, “How will this fixture perform in the actual project space?” Unfortunately, most projects lack the budget and timeline to create a full-scale mock-up that would prove the fixture capable or incapable of meeting the design goals before installation. Luckily, specifiers can use photometric reports to predict how a lighting fixture will perform in a specific application.

Photometric reports describe how a fixture distributes light, how efficiently it is distributed, and how likely it is to produce glare or unwanted patterns. A comprehensive photometric report contains a lot of information. Two of the most important items to review in order to assess the distribution pattern of a particular fixture are the candela chart and the candela distribution curve.

The Candela Chart

The candela chart displays the relative light intensities (measured in candelas) of a fixture at various vertical and horizontal viewing angles. To first describe a vertical and horizontal viewing angle, imagine a hanging, 2-by-4 linear direct/indirect troffer fixture. The vertical axis of the troffer is an imaginary line that runs through the center of the fixture from a point directly beneath the fixture on the ground (0 degrees) up to a point on the ceiling directly above the fixture (180 degrees). The horizontal axis runs through the center of the fixture from end to end (90 degrees to 270 degrees). A person standing at one end of the fixture (90 degrees) could measure the intensity of the light at various points along the vertical axis (0 to 180 degrees) called vertical viewing angles and gather all of the light intensity values for that one vertical plane of the fixture from that one specific horizontal viewing angle (90 degrees).

If the fixture emitted a perfectly symmetrical pattern of light in all directions, the entire lighting distribution pattern could be detailed from this one group of measurements. However, most fixtures do not emit a symmetrical pattern of light in all directions, so more measurements need to be taken. The candela chart displays the lighting intensity measurements taken for entire vertical planes (0-180 degrees) at various horizontal viewing angles (0, 22.5, 45, 67.5, and 90 degrees) around the fixture. The candela chart displays the horizontal viewing angles across the top as the column headings and the vertical viewing angles (increments between 0 and 180 degrees) as the row headings.

Specifiers may use photometric reports to predict how a fixture will perform in a space. Photo courtesy of Bock Lighting

 

This is the candela chart for the lighting fixture pictured above and it illustrates the way that the fixture distributes light.

 

Here is an example of the candela chart for an architectural fixture with a reflector lamp. The candela chart is the table in the center with the column headings: Ang., CP, and Lum. The vertical viewing angles (0-180 degrees) are found along the right-side column and the associated light intensities (in candela) are under the middle column header CP, which stands for candela power. The candela chart illustrates that this particular fixture is a direct fixture only emitting light below the 90 degree angle and emitting zero candelas at 90 degrees and above. The light intensity at zero degree (a spot directly below the fixture) is 1026 candelas and is the viewing angle with the greatest lighting intensity. At the 25 degree viewing angle, the fixture emits a light intensity of 930 candelas and at the 55 degree viewing angle, 620 candelas are measured.

The Candela Distribution Curve

The candela distribution curve graphically illustrates the lighting distribution pattern of the fixture. This circular (or semi-circular) graph places the light source at the center and maps the various light intensities (in candelas) in incremental steps up the vertical plane (0-180 degrees) for a single horizontal viewing angle. The plots for multiple horizontal viewing angles can be laid over one another onto one distribution curve to better illustrate changes in the direction and intensity of light output that a person would experience as they walked around the fixture from one horizontal viewing angle to another.

There are a few important characteristics about the lighting fixture and how the lighting fixture will perform in a space that are quickly revealed by referencing the candela distribution curve. It can be an easy way to compare the lighting distribution of multiple fixtures of interest. First, the distribution curve will illustrate if the fixture is direct (emits light only below the horizontal axis), indirect (emits light only above the horizontal axis), or direct/indirect (emits lights both above and below the horizontal access). The distribution curve also reveals if the fixture distributes light in a focused spotlight pattern or a wider flood pattern. A fixture with a focused and spot distribution will have a relatively narrow distribution curve with light remaining either above or below the light source in the center of the graph, whereas a medium or wide floodlight will have an increasingly wider distribution pattern.

The candela distribution curve can also expose potential performance issues that a fixture may have, such as disruptions in the distribution pattern or a propensity for glare creation. A smooth and rounded candela distribution curve indicates that the light fixture will produce a smooth light pattern, whereas striations in the distribution pattern indicate that the fixture may cause inconsistent illumination and streaking in the space. The candela distribution curve can also reveal if a fixture is likely to produce glare. Fixtures that emit high-intensity (300+ candelas) light in the vertical viewing angle range of 55 to 90 degrees are considered at higher risk for creating glare in a space.

It is important to note that each candela chart and candela distribution curve is generated to reflect the performance of a specific fixture and lamp combination. Making changes to the lamp, fixture, or aspects of the fixture can materially alter the candela chart and candela distribution curve of the fixture.

The data found on a candela chart can be entered into lighting design software for more detailed analysis of the lighting fixture’s distribution of light and potential performance issues. Many manufacturers make this information readily available for their specification-grade fixtures. These files are typically produced in the standard format created by the Illuminating Engineering Society (IES) and are often referred to as IES files.

The candela distribution curve is the visual representation of the lighting intensity information captured in the candela chart.

 

Here is the candela distribution curve for the architectural lighting fixture with the reflector whose candela chart was examined in the section above. The candela distribution curve is the visual representation of the lighting intensity information captured in the candela chart.  The candela chart captured the measurements for one horizontal viewing angle and that single horizontal viewing angle is represented in this single distribution curve. The curve intersects the zero degree vertical viewing angle at 1026 candelas. The candela power for the fixture decreases at each subsequent viewing angle until it reaches zero candelas at the 90 degree viewing angle. The smooth, rounded curve indicates that the lighting fixture will produce a smooth lighting pattern free of gaps in illumination.

Selecting the Right Lamp Type: Color and Efficiency

While the architectural lighting fixture may determine how the light is distributed in a space, the lamp type determines the type of light being distributed and the energy and material efficiency of the system. Fluorescent, compact fluorescent, halogen, high-pressure sodium and light emitting diodes (LEDs) are a few of the lamp types available in architectural lighting fixtures. Each lamp type offers a unique combination in terms of the color composition of the light they emit and the efficiency with which they provide it. Knowing more about each specific lamp type will enable a design team to choose the type of lamp that best fits the ambient and energy performance needs of the project.

Color Quality

The ability to see color is dependent upon the kind and quality of light available. The color of a sweater or piece of fruit that registers in the human eye is actually a reflection of the light in the space bouncing off of the object being examined. This explains why the same item will look different under different types of light. The same red rose that looks brilliantly red outside on a sunny day may look almost black under a low-pressure sodium streetlight at night.

The Color Rendering Index, or CRI, assigns each light source a value that describes how the light it emits compares in color quality with natural daylight, which is considered the gold standard. Natural daylight has a CRI index rating of 100. In comparison, low-pressure sodium vapor lamps, the popular monochromatic parking lot light sources that bathe objects in an unnatural yellow hue, receive a CRI index rating of 0. The higher the CRI rating of a lamp source, the better the color quality of the light it creates.

Both halogen and incandescent lamps top the CRI rating scale, both receiving ratings of close to 100, however the light output from halogen lamps actually appears whiter and brighter due to a higher concentration of blue and green wavelengths in the light output. Technological advancements in other lamp types have significantly improved the CRI ratings that can now be attained with other lamps.  For example, fluorescent lamps are now capable of providing light with a better color quality than the cool white light (CRI rating 62) with which they were synonymous for so many years. Fluorescent lamps today can provide light with a color quality rating that ranges from 52 to 95, depending upon the specific lamp being considered.  The CRI rating for a Standard Clear high pressure sodium lamp may be as low as 21, but the rating can be as high as 70 for the Improved Clear or Color-Improved Diffuse-Coated lamp varieties. Clear metal halide lamps can be found with a rating of 65 and phosphor-coated metal halide lamps can receive a rating of up to 70. Phosphor-converted LED lamps can also score relatively high on the CRI scale with a range of 70 to 90+.

Technological advancements in lamp types have significantly improved the CRI ratings that can be attained by a variety of lamp types.
Lamp Type	CRI Rating
Incandescent	100
Halogen	100
Fluorescent	52—95
High-Pressure Sodium	21—70
Metal Halide	65—70
LED	70—90
Low-Pressure Sodium	0

 

Selecting a light source with a higher CRI rating will protect the integrity of the appearance of the merchandise or food under the illumination.

Efficiency

Two different factors are considered when determining the overall efficiency of a lamp type. Those factors are lamp efficacy and rated lamp life. The efficacy of a light source is measured in terms of the number of lumens produced per Watt (LPW). Higher ratios indicate more efficient light sources, because more light is being produced with less energy. Rated lamp life indicates the number of illuminated hours that one lamp is expected to last before needing to be replaced. Selecting a lamp type with a longer rated life will minimize the necessary maintenance and the material lamp waste created throughout the life of the system.

Fluorescent

The efficacy of a fluorescent lamp is dependent upon many different factors including lamp color and lamp length. These lamps can produce a range of 30 to 110 LPW, making their efficacy three to seven times higher than an incandescent lamp source. It should be noted that fluorescent lamps are affected by extremes in ambient temperature. Optimal operation will occur at temperatures between 5 and 25 degrees Celsius. Below this range there is a rapid drop in light output and efficacy. The rated lamp life for a linear fluorescent tube is between 7,000 and 24,000 hours, depending upon the specific lamp style selected.

Compact Fluorescent Lamps

Compact fluorescent lighting (CFL) consumes up to 75 percent less energy than incandescent lights and generate 50-70 LPW. The lamps last up to 10 times longer than the incandescent standards, illuminating areas for almost 10,000 hours per lamp.

Halogen Lamps

Producing 15-20 LPW and offering a much longer lamp life (between 2,000 and 4,000 hours), halogen was more efficient in both energy and materials than the incandescent bulb. As an added bonus that maximum efficacy is maintained throughout the life of the lamp.

Today, halogen lamps are available in a variety of lamp types. The two most common halogen lamp types are a parabolic aluminized reflector (PAR) and a multi-faceted reflector (MR). Both lamp types produce a significant amount of heat while operating.

Metal Halide Lamps

Metal halide lamps offer a better efficacy (70 to 115 LPW) than compact fluorescent, halogen, and incandescent lights. This lamp type requires a ballast to provide proper starting and operating voltages, which contributes toward the higher price tag often associated with metal halide fixtures. However, the higher initial cost is balanced by a low cost of ownership. Metal halide lamps will provide more light on a project, more efficiently, and for a longer period of time (rated lamp life ranges from 5,000 to 20,000 hours) than the less costly halogen alternatives.

High-Pressure Sodium Lamps

High-pressure sodium lamps have an efficacy of 50 to 140 LPW—an efficacy exceeded only by low-pressure sodium lamps—and an impressively long lamp life rated for between 16,000 and 24,000 hours.

LEDs

LEDs, also referred to as solid state lighting (SSL), are the newest and latest light sources used in lighting. Highly efficient, these sources are able to create 30-100 LPW. Beyond improved energy efficiency; the system life is much longer than other available light sources. LEDs are rated to operate for between 35,000 and 50,000 hours before needing to be replaced. This long life significantly reduces the maintenance required by the system and the number of lamps sent to landfills every year.

Although LEDs are highly efficient, they do generate some heat, so it is important that the lighting fixture is capable of heat management. Most importantly, the diodes are very heat sensitive and excessive exposure to heat will seriously diminish or completely fail an LED board.

Considerations for Selecting Exterior Fixtures

Lighting fixtures destined for the outdoors must be designed to accomplish two objectives. First, moisture must be kept out of the area housing the socket and the lamp. If the socket becomes wet, the fixture will short out. Second, the heat created by the lamp when it is illuminated must be managed. If too much heat builds up around the lamp, the lamp will overheat and fail prematurely.

Select an outdoor fixture that is made of metal so that it can provide a watertight housing, keeping the socket and lamp dry, and manage the heat created by the lamp. Photo courtesy of Bock Lighting

 

The pursuit of this watertight and, simultaneously, cool environment is challenging because in order to keep dew, rain, snow, and other condensation away from the socket, the area must be airtight. In an airtight setting, neither moisture, nor air, nor heat can pass freely from the source to the exterior. Instead, the physical fixture becomes responsible for dissipating the heat.

The need to manage heat is the reason that high-quality outdoor fixtures are made of metal. It is also the reason that plastic fixtures are usually short-lived. Brass and aluminum effectively absorb the heat created by the light source, acting similar to a heat sink. The heat transfers from the lamp housing to the metal fixture and then radiates from the fixture into the environment.

Beyond functionality, another benefit of using brass and aluminum in the body of the fixture is that both metals are renewable and recyclable. Brass is the combination of copper and zinc and, today, almost 90 percent of all brass alloys are recycled. Aluminum is the most abundant metal in the Earth’s crust, and the third most abundant element overall, following oxygen and silicon. Soda cans, scrap metal, lighting fixtures and all other things aluminum can be recycled.

Considerations for Selecting More Sustainable, American-Made Lighting Fixtures

Beyond designing a lighting plan that minimizes energy waste by delivering the necessary light when and where it is needed and selecting a lamp type to meet the energy consumption goals of the project, design teams can further reduce the environmental footprint of the lighting system by selecting fixtures made from recyclable or recycled materials, finished in environmentally-friendly powder coating, and ultimately qualifying as Made in America.

The Environmentally Friendly Powder Coat

Powder coating is the fastest-growing finishing technique in North America and for good reason. As demand for more environmentally conscious manufacturing processes grows, more products are turning away from solvent-based wet paint solution and toward the toxin-free powder coating process. The powder coating process is used to apply a decorative and protective finish to a wide range of metal parts without the use of any solvents, eliminating VOC emissions.

The powder is a mixture of finely ground particles of pigment and resin, which is sprayed with a special spray gun that electro-statically charges the powder. The charged powder adheres to the electrically grounded metal parts. Then the powder is heated to its melting point and fused into a smooth coating in a curing oven. The result is a uniform, high-quality and attractive finish that is highly durable, and resistant to scratches, cracking, peeling, UV rays and rust. 

Powder-coated lighting fixtures are available in variety of colors, a wide range of glosses, and diverse textures.

Powder Coat Warranty

While the powder coating process may be described similarly from manufacturer to manufacturer, the durability of each powder coat can be significantly different. The American Architectural Manufacturers Association (AAMA) is the group within the aluminum products industry responsible for certifying that a powder coat warranty is accurate. The warranty guarantees that the finish on the interior or exterior aluminum fixture will withstand the elements for a specified period of time. In order to verify these claims, the AAMA certification process places materials under a variety of stresses designed to simulate an extreme outdoor experience including intense heat, salt spray, boiling water and abrasion tests.

The Buy American Provision of the ARRA

On February 17, 2009, Congress passed the American Recovery and Reinvestment Act of 2009 (ARRA), in an effort to counter the negative effects of a recession that devastated the economy and resulted in unfinished building projects and lost jobs. The ARRA appropriated more than $700 billion to fund federal tax relief, expansion of unemployment benefits, and domestic spending in healthcare, education, and infrastructure.  Projects that meet certain criteria may qualify for stimulus funding under ARRA. The ARRA includes a “Buy American” provision that encourages support of domestic companies and US workers. This includes specific requirements about the origins of manufactured goods to be used in projects receiving stimulus money. Products designed, assembled, and painted in the US may comply with this standard, although they may contain materials and components from local, national, and international partners. Specify lighting fixtures classified as “American-Made” that qualify for use under the “Buy American” provision of the ARRA to take advantage of this stimulus funding.

Bock Lighting, founded in 2009 strives to be an innovator in the lighting industry with its quality products and service. Bocks founders have decades of experience in the lighting industry, known for their innovation and commitment to quality.  www.BockLighting.com