IMAGE OF A LIBRARY WITH TEXT OVERLAY THE DESIGN BRIEF, A DAKOTA DESIGN CO PRODUCTION, COMPLIMENTARY, LESSONS FROM DESIGN SCHOOL

Interior designers need to understand the attributes of LED lighting to make informed choices about both lamps (commonly referred to as light bulbs) and luminaires (commonly referred to as lighting fixtures). Lighting can elevate and transform an environment, and with the increased complexity of LED technology, and the related energy-efficiency building codes, being a well-informed designer is critical.

Why Are LEDs Becoming Universally Used?

LEDs (light-emitting diodes) have largely displaced other types of light sources. Incandescent and halogen light sources are very energy inefficient. They require a lot of energy for operation and emit lots of heat—which in turn requires even more energy to cool a space. Fluorescents, although more energy efficient than incandescents, also use far more energy than LEDs.

Effective fairly recently (August 1, 2023), the manufacture and sale of any bulb that does produce at least 45 lumens per watt (a lumen is a measure of brightness, watt is a measure of energy usage—more about that later) is prohibited in the United States. Since incandescents need much more energy to burn brightly, they can no longer be produced per this legal requirement. (There are a few exceptions that can still be manufactured, such as the small bulbs used in your refrigerators).

Compact fluorescents (CFLs)—although more energy efficient than incandescents—are next on the chopping block. They require more electricity than LEDs, and contain mercury, which can be a hazard if the bulbs are not disposed of properly. And most CFLs are not dimmable. DImming is a good energy savings strategy. Some states have banned CFL manufacture already, but all of the US is expected to follow suit when the energy requirement for bulbs is increased to at least 100 lumens per watt, which is expected to take place by 2025.

So—as a point of reference—current LED lamps (bulbs) typically produce 75-110 lumens per watt. Remember, lumen = brightness, watt = electricity used. Even more efficiency is possible, as we will see in upcoming years. That makes LEDs 7 to 10 times more energy efficient at producing light than incandescents (10-15 lumen per watt), and about twice as energy efficient as CFLs (50-75 lumen per watt)

And the life of LEDs far, far exceeds that of incandescent bulbs, meaning less labor for replacement and less waste in discarding used bulbs. LED bulbs may burn for 25,000 hours (many years) compared to the 500 to 1000-hour lifespan of incandescents.

The bans on lower efficiency bulbs—meaning that soon LED bulbs will be the only purchase option—do not present an issue to designers or homeowners, though, because LEDs are manufactured in the same shapes as older bulb varieties, so they can fit into all existing lamps and light fixtures.

What Do LEDs and LED Bulbs Look Like?

A light-emitting diode itself is a very small chip, often about ¼” x ¼,” constructed by sandwiching a layer of Phosphor between two silicon wafers, and is often encased in an optical lens that can help direct the light. Think of the diode (the light source) as a computer microchip or semiconductor that creates visible light when an electrical current is passed through it.

Looking back in time, the original shape of the traditional incandescent lightbulb, interestingly, was derived from the internal workings of early electric light technology. The shape was bulbous to accommodate the long and hot-burning filament. This bulb shape is sometimes called the Edison bulb, for its creator, but is more accurately called an A lamp.

The more decorative candle bulb, and globe bulb shapes—called CA and G bulbs, respectively—also have shapes that accommodate the spreading hot filaments within a spacious glass encasement.

When LED technology was initially introduced, people were slow to adapt to it, mainly because small LED bulbs looked nothing like the bulbs we were familiar with. LEDs do not use filaments, and the light-emitting diodes that create the light are quite tiny.

The path of least resistance was to adapt LED technology to the same shapes we creatures of habit were used to. That was much easier than trying to convince homeowners to get rid of every existing light fixture (luminaire) that utilizes a traditionally shaped bulb. So, manufacturers started producing LEDs in the same familiar shapes that work within the countless existing table, floor, and mounted lamps in millions of homes.

The LED bulbs shown below—in the shapes of A, CA, and G shaped bulbs—are manufactured for use in these existing light fixtures. The tiny LED chips (or diodes) are encased within. This volume and shape of glass encasement is certainly not required to house a tiny LED chip, but these bulb shapes work for us because they fit into our existing light fixtures.

LEDs are also made in the same shapes of parabolic incandescent (PAR) and MR-16 halogen (MR) bulbs to be retrofitted into existing light fixtures that used those bulb types.

LED bulbs are even produced to look like they have the familiar glowing filaments, spreading out within a bulbous glass globe. The tiny light-emitting diodes are arranged along a wire-like filament, which is then enveloped by a clear or frosted glass bulb, making them look remarkably like the old incandescent technology.

LEDs are also made to be retrofitted into tubular fluorescent fixtures. This image shows the diodes inside an LED bulb in the traditional shape of a fluorescent tube.

Absence of UV Radiation, Another PLUS for LEDs

An additional benefit to light produced by LED sources is that LED does not emit any UV (ultraviolet) radiation. The primary source of ultraviolet light is the sun, but light produced by fluorescents and incandescents also contains UV. Ultraviolet light is the culprit that can fade and discolor fabrics and artwork by breaking down the chemical bonds in dyes and pigments over time. Because LED light sources produce NO ultraviolet radiation, fading and discoloration is not a risk.

There are several other terms to be aware of to fully understand LED technology.

Terminology: LUMENS and WATTAGE

For those designers who have been around awhile, the output brightness of a lamp (light bulb) used to be simple. When incandescent lamps (bulbs) were used, a 100-watt light put out much more light than a 60-watt bulb, which put out more light than a 25-watt bulb. We became accustomed to using wattage as an indication of how bright the bulb would be. With incandescents, this was a reliable indicator of how much light the bulb would emit.

The brightness of LEDs is determined a bit differently, though. Wattage is really the measurement of the amount of electricity consumed to power a lamp, not the brightness of the output. With LED lamps, wattage is no longer a meaningful determination of how bright an LED will shine, as ALL LEDs use far less wattage than ALL incandescents. So, it is no longer applicable to use wattage to determine brightness.

The appropriate gauge for measuring the quantity of light emitted from an LED lamp is LUMENS (lm). The higher the Lumen number for a light source, the more light it emits.

Lumens—as a measurement of light—is somewhat like the concept of footcandles with one important difference. Lumens and footcandles are both units of measurement used to describe light intensity, but they differ. Lumens is a way of quantifying the amount of light produced by a source. Footcandles is a measurement of how much light from a light source is shining on one square foot of a particular surface.

Footcandles do not define how bright a light source is; lumens do. Footcandles provide information about how bright a surface is illuminated from a light source, depending on distance and beam angle. With LED lighting, Lumens is the information provided, because it is easier to measure, understand, and compare.

As a comparison for those who are very used to incandescent wattage as a gauge of brightness, here is a breakdown of comparable lumens for equivalent brightness, and actual wattage (energy usage) for an LED light source of that brightness.

Terminology: KELVIN and CHROMACITY

Light itself can vary greatly in hue. We are all familiar with the warm, orange-ish color that comes from the sun at sunset. It is quite different from the light from the sun in the morning (which is quite blue). And the sun’s light in the autumn —which is very warm in the northern hemisphere—is quite different than winter’s light—which is much cooler or blue-er. And we all know how very yellow (and complementary to our skin tones!!) light from a candle is.

In decades past, when our lamp choices were incandescent, fluorescent, or halogen, it was easy to anticipate the color output. Incandescent bulbs—where an electric current heats a tungsten filament until it becomes white hot and glows—naturally produce a warm, yellowish light. Halogen bulbs (such as the very popular MR16s)—also use a heated filament to produce light, but encased within halogen gas and a quartz casing—can produce a very bright, white light. Fluorescent lamps—illuminated when electric current charges encased mercury or sodium vapor—emitted a cooler light.

But LEDs can be programmed to emit any color within the visual spectrum. So, designers must choose the desired light hue, or Chromacity of the LED light source they are specifying.

The spectral quality of LED light—sometimes called color temperature—is measured in Kelvin (K). The lower the number on the Kelvin scale, the warmer (yellower) the light. Higher Kelvin numbers equate to cooler (bluer) light.

As a point of reference, very yellow candlelight is equivalent to about 1800 Kelvin. Traditional incandescent bulbs emit light at about 2700K. Halogen bulbs were whiter, at about 3000K, and fluorescent bulbs at about 3500K. Natural daylight at noon—which is fairly cool—is about 5000K.

LED bulbs are generally available in colors from 2000 Kelvin to 6000 Kelvin. Designers need to choose the light color appropriate for a space, and need to consider how finishes and materials look within that color temperature. A designer may choose to light a moody, sophisticated powder room at 2000K, and a home office at 3500K. Nice, warm light is about 2800K. Generally, ambient lighting is often specified at 3000K.

Below is a general guide, but designers should take latitude in choosing Kelvin to achieve their desired effect.

Terminology: COLOR RENDERING INDEX (CRI)

Another consideration that comes into play—particularly when lighting artwork—is how faithfully a light source shows the true color of an object. It would be wrong to shine a very warm light source on Monet’s Waterlily paintings, which are very purple-blue. The true colors used by the artist would be distorted, and the vividness of the painting’s subject matter would be lost.

The measurement used to rate how accurately a light source reveals the genuine colors of an item being lit is Color Rendering Index, or CRI. CRI ratings are from 1 to 100, with higher numbers indicating better color rendering capacities. Where color appearance is very important, as with artwork, a light source with a CRI of 90 or above should be specified.

Chromacity of color and color rendering capabilities do not necessarily align across light sources. Two different lamps (light bulbs) can have the same Kelvin measurement, but quite different CRIs. Designers should rely heavily on lighting vendors to assist with lamp choices for important applications.

So remember these terms and measurements for light sources:

Watts - energy usage
Lumens - output and brightness
Kelvin - measurement of chromacity or light hue
CRI - how well a light source renders colors accurately

What to Know About DImmers and Dimming

Light dimming (reducing output from a light source) is an important strategy to conserve energy by using less power when lower light levels are appropriate, and can extend the life of a lamp (light bulb). Dimming also accommodates different times of day and various activities by adjusting light levels.

The 2024 International Residential Code, Section N1104.2, and the 2024 International Energy Conservation Code, Section R404.2.1, now require that all permanently installed lighting fixtures in new residential construction are controlled by a dimmer, OR have an occupant sensor (motion sensor) that automatically turns off lights after 20 minutes of inactivity. This requirement does not apply to hallways, bathrooms, exterior, or security lighting within homes.

Although all states and municipalities have not yet adopted these requirements, the overarching goal is obviously to reduce energy consumption in two events:

Lighting levels (lumen output) are higher than needed or desired, and energy usage could be lessened with lower, more appropriate light levels
Energy is wasted because lights are left on in rooms that are not occupied

With traditional incandescent lamps, a dimmer reduces the amount of electrical current powering the light source, which causes the filaments to glow less brightly.

With LEDs, dimming is a bit more complex because lowering the flow of electricity to a low-energy consuming LED light source does not react in quite the same way. LED lamps contain a small driver that converts alternating current (AC) electricity to a lower current to power the LED microchip. A dimming device must be compatible with the internal LED driver. Virtually all LED bulbs on store shelves today have dimmable drivers and can work with any wall switch dimmer. But certain LED products—LED strips for instance—may not work appropriately with a wall dimmer. Often, the packaging on an LED bulb will indicate “Dimmable.”

The other important factor is that, with LED bulbs, often the chromacity of the light changes as the electrical current is reduced. This may cause a 2700K LED light source to become much whiter (higher Kelvin) as it is dimmed. This is usually the opposite effect than what is desired. Usually, a warmer, more intimate light is wanted when a light is dimmed, not a cooler or whiter light. Check for LED packaging that indicates “warm dimming” when selecting a low Kelvin LED lamp, to ensure it will remain warm as the light level is dimmed.

Design Possibilities With LED Technology

The real beauty of LED lighting technology goes way beyond encasing it in traditionally shaped light bulbs!! Because of the tiny size of an actual light-emitting diode, LED fixtures can be made into remarkable shapes and curves, and can be easily embedded into glass or within a metal extrusion, allowing just a bit of air space for heat dispersion. The design possibilities for LED technology are endless and the future will hold many remarkable innovations in form and effect. It will be interesting to see the creative LED lighting innovations coming to the marketplace in the next ten or twenty years!