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; 0.1 IACET CEU*; 1 GBCI CE Hour; 1 AIBD P-CE; 1 IDCEC CEU/HSW; 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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Light Reflectance Value (LRV)

An important consideration when selecting paint is the paint’s light reflectance value, or LRV. This figure represents the total quantity of visible and usable light reflected by a surface at all wavelengths and in all directions. Put another way, LRV measures how much light a surface reflects and how much light it absorbs.

LRV is largely dependent on color. This quality is measured as a percentage from 0 to 100, where zero is absolute black and 100 percent is perfectly reflective white. In reality, the most absorbing black has an LRV of about 5 percent, and an extremely reflective white has an LRV of about 90 percent.

LRV has important implications for daylighting and energy use. Dark colors absorb more light and heat; consequently, spaces painted with darker colors may require more artificial light to light them. They may also require more cooling energy or less heating energy, depending on the building location, orientation, and other factors. If heat gain is a concern, a good rule of thumb is to choose colors with an LRV of 60 and higher.

Lighter colors reflect more light back into the room and absorb less heat. A color with a high LRV will contribute most to daylighting and can reduce reliance on artificial light sources. Naturally, whites have high LRV values, but colors in the yellow family can achieve LRVs of up to 80 percent or 90 percent. An important consideration is that yellow grows exponentially more intense the more area it covers.

Knowing the color’s LRV can help the designer ensure adequate illumination for tasks and general lighting. LRV can also help delineate spaces and highlight hazards by optimizing contrast. Designers can often find the LRV of a paint color on the opposite side of the fan deck or through the manufacturer’s website.

Importantly, LRV is an invaluable tool for creating successful lighting plans that optimize daylighting and reduce reliance on artificial lighting. Commercial spaces such as auditoriums, classrooms, banks, lobbies, museums, and restaurants have a suggested LRV of about 70 percent. Industrial spaces such as warehouses, manufacturing, and shipping facilities have a suggested LRV of 65 percent.

ASHRAE also recommends minimum reflectance values for interior ceilings, walls, and flooring for various building types. The ceiling is the most important light-reflecting surface; hence, the recommended reflectance values are high—80 percent or more. Reflectance values for walls should be at least 50 percent, and at least 20 percent for floors.

Photo courtesy of Benjamin Moore & Co.

Reflectance and Paint Sheen

The type of finish on the paint affects how light is reflected from a surface. This, in turn, impacts how light is distributed within a space—and ultimately, how we experience it.

Think about a glossy versus a matte finish. The glossy surface will have more variation, with highlights that appear white or nearly so, while the matte surface will have a more uniform color.

To understand why this is, it’s helpful to understand the two main types of reflection: specular and diffuse.

Specular reflection is the mirror-like reflection of light from a surface. Incoming light from a single direction reflects off the surface in a single outgoing direction. Satin, semi-gloss, and gloss sheens produce specular reflection.

Specular reflection creates highlights on glossy surfaces, especially those with texture and “topography,” like molding. While specular reflection tends to make surfaces more interesting, it can also induce glare, which can cause fatigue and eyestrain.

Diffuse reflection occurs when incoming light is reflected in many directions. Matte, flat, and eggshell paint sheens produce diffuse reflections.

Diffuse reflection makes surfaces appear matte and uniform. This type of effect tends to obscure surface defects and can help contain glare; however, it creates a more monotonous painted surface.

Photo courtesy of Benjamin Moore & Co.

Impact of Sheen on Color Perception

Because of the way light reacts to glossy surfaces, light colors can appear lighter, and dark colors can appear darker in glossy sheens. Intuitively, it makes sense that the highlights in a glossy finish can make the color appear lighter. With darker colors, there is a greater contrast between the lighter highlights and the rest of the surface where light is not reflected. The overall effect is for the color to appear darker.

    To summarize:
  • Matte, Flat, Eggshell tend to produce a diffuse reflection
  • Satin, Semi-Gloss, and Gloss will produce a specular reflection
  • Darker colors may appear darker in higher sheens
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Originally published in Architectural Record
Originally published in June 2022