The Science of Light and Its Impact on Paint Color, Specification, and IEQ

Using artificial and natural lighting to help specify paint for healthy spaces
Sponsored by Benjamin Moore & Co.
By Andrew A. Hunt
1 AIA LU/HSW; 1 IDCEC CEU/HSW; 1 GBCI CE Hour; 0.1 ICC CEU; 0.1 IACET CEU*; 1 AIBD P-CE; AAA 1 Structured Learning Hour; This course can be self-reported to the AANB, as per their CE Guidelines; AAPEI 1 Structured Learning Hour; This course can be self-reported to the AIBC, as per their CE Guidelines.; MAA 1 Structured Learning Hour; This course can be self-reported to the NLAA.; This course can be self-reported to the NSAA; NWTAA 1 Structured Learning Hour; OAA 1 Learning Hour; SAA 1 Hour of Core Learning

Learning Objectives:

  1. Describe how color affects the symbolic, emotional or associative perceptions of occupants, and in turn, their health, safety and well-being.
  2. Explain how correlated color temperature (CCT), color rendering index (CRI), and spectral power distribution (SPD) impact the quality and color of light.
  3. Distinguish the CCT and CRI of different artificial light sources, and describe their effects on color.
  4. Provide examples of how design professionals can use their knowledge of light to create designs that support the health and well-being of the occupant.

This course is part of the Interiors Academy

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Depending on the type and age of a building, you may encounter a range of artificial lighting systems, from incandescent and halogen to fluorescent and LEDs. Often buildings will include a combination of lighting types and will supplement artificial lighting with daylighting.

You likely understand intuitively that certain colors look more appealing when illuminated by certain types of artificial lighting compared to others. These differences can largely be explained by the differences in color temperature, color rendering index, and efficacy (efficiency) of these light sources. Understanding these characteristics can help design professionals select the ideal paint color for both residential and commercial projects. It can also help designers take into account how artificial lighting systems and color impact occupants’ well-being and productivity.

Photo courtesy of Benjamin Moore & Co.

Incandescent Lighting

The incandescent, or Edison bulb, has been with us for over 100 years, with the basic technology unchanged. These lamps produce light via a tungsten wire filament that is placed inside a glass bulb. When an electric current is passed through the filament, resistance in the filament creates heat, and the bulb glows. As we saw earlier, the spectral power distribution graph for incandescent lighting shows that there is much more energy toward the red end of the spectrum, which explains why incandescent bulbs produce such warm light.

Incandescent lighting has a CCT of about 2700 K and its CRI is 100, meaning incandescent lamps are very good at rendering color. Unfortunately, these lamps are highly inefficient. About 90 percent of the energy is lost as heat, and their life expectancy is short. Consequently, incandescent lamps are being rapidly phased out in the name of energy efficiency. The United States has set efficiency standards that, in effect, preclude the manufacture or importation of certain incandescent lamps. As of this writing, a second tier of even more stringent standards has been delayed.

Halogen Lighting

First patented by General Electric in 1959, halogen lighting is considered a type of incandescent lighting, but with several advantages over the Edison bulb.

Halogen lighting is about 20 percent more efficient than conventional incandescents. More energy is released as light, and the lamps have a longer service life. The bulbs burn at a continuous level of brightness and have a life span of about 2,000-3,000 hours.

The spectral power distribution of halogen lamps is the closest of all light sources to daylight; it’s relatively balanced across the visible spectrum. Consequently, halogen is considered an ideal light source.

The color temperature of halogen is approximately 3000K, which is considered “warm” light, and it renders color at 100 percent. This relatively high color temperature enables good color rendition across a wide range of colors.

On the downside, halogen lamps have a high operating temperature, and while they are more efficient than other incandescents, they are far less efficient than LEDs. Hence, many countries have begun phasing them out, and in the United States they are rapidly being replaced by LEDs. Also, the light quality is not consistent. Though bright and white at maximum output, when dimmed, halogen light appears amber.

In addition to specific applications in homes and commercial buildings, such as task lighting, halogen lamps are also used for film projectors, vehicle headlights, floodlights, work lights, and in film production.

Fluorescent lighting

Though the technology was developed in the 1880s, the first fluorescent lamps weren’t available commercially until the 1930s. These lamps work by exciting a vapor inside a glass tube. As electricity passes between tungsten cathodes, the mercury vapor releases ultraviolet energy. A phosphor coating on the inside of the tube converts the UV light into visible light—a process called fluorescence.

Fluorescent lamps require a ballast, which controls the current to the lamp. The current must be modulated as the gas inside the tube ionizes and the resistance lowers; otherwise, the lamp would destroy itself.

From classrooms to grocery stores, fluorescent lighting is widespread in commercial and institutional buildings. Fluorescent lighting is seen in residential settings, particularly kitchens, and compact fluorescent bulbs, or CFLs, have replaced the traditional Edison bulb in many homes.

The light produced by early fluorescent lamps was cold and undesirable; however, phosphor technology has improved, resulting in more pleasing light with higher CRIs.

The spectral power distribution graph for fluorescent lighting reveals spikes at the red, green, and blue wavelengths, with little or no output at others. Colors appear cool. Blues and greens are enhanced, while reds and yellows are muted.

Fluorescents are available in a range of color temperatures, from warm whites (2700 K) to cool white (6500 K), and they have CRIs in the 80-plus range. They have a life span of about 8,000-10,000 hours.

There are several types of fluorescent lamps. Linear, or tube lights, remain popular for their energy efficiency and their even, diffuse lighting.

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Originally published in Architectural Record
Originally published in June 2022