Photo courtesy of PPG Industries Inc.
In architecture and design, it’s important to understand the impact colors have on both the appearance of an internal environment, as well as potential heat build-up of external surfaces. Understanding how a color will look in an environment helps to plan lighting, while also creating visual contrast where needed.
How light or dark a color appears is determined by how much light the color reflects. Light reflectance value (LRV) is the total amount of visible and useable light reflected by a surface in all directions when illuminated by a light source. LRV is measured as a percentage between 0 and 100, with absolute black being 0% and perfect white 100%.
“LRV is an important value for designers or architects as it provides an indication as to how light, dark or bright a color will be and how it will contribute to the overall aesthetic, mood or feel of a project,” explains Michelle Vondran, technical manager at NS BlueScope Coated Products North America, Rancho Cucamonga, Calif.
Higher LRV numbers mean more visible light is reflected, and lighter colors typically have higher numbers than darker colors. However, texture can also impact LRV, as rough textures tend to reflect less visible light. Knowing a color’s LRV is important when choosing coordinating colors or creating a mood. LRV is also beneficial in making energy-efficient decisions, as a lighter color with a higher LRV won’t require as much air conditioning or lighting as a darker shade with a lower LRV that warms quickly and soaks up light.
Gary Edgar, architectural specification manager for Pittsburgh-based PPG Industries Inc.’s Building Products, notes that color selection can notably affect the lighted appearance, glare and the energy costs of a structure. “The darker the color, the more light can be absorbed. Conversely, the lighter the color, the more visible light is reflected,” he says. “The same balance is typically true the absorption of energy/heat, a light color absorbs less heat.”
Brad Shreve, building and construction segment lead–Americas at AkzoNobel Coil & Extrusion Coatings, Columbus, Ohio, says how dark or light a color is and its associated LRV can alter how a space can appear (bright, spacious, dark, confined, etc.). “These days, movements towards eco-friendly buildings make use of higher LRV coatings, which can require less artificial light therefore reducing energy demand.”
Solar Reflectance Value (SRV)
While LRV measures the amount of visible light that a surface reflects, solar reflectance value (SRV) measures the amount of total solar radiation, visible, infrared and ultraviolet, that is reflected from a surface. SRV is expressed as a percentage from 1 to 100, with the higher the number, the more solar radiation that is reflected. Similar to LRV, light-colored objects tend to have a higher SRV, while dark colors have a low SRV. However, with the introduction of “cool” pigments, it is possible for a medium to dark color to have a high SRV. And, the higher the SRV, the cooler the surface stays in direct sunlight.
Vondran explains that LRV is often confused with solar reflectance, which measures the thermal properties of a surface, as well as gloss and/or sheen, which measure the gloss or shine of a surface. “We are seeing LRV specifications in some building codes and they typically want a mid- to low-LRV value (think midtones and dark colors),” she notes. “While the intent of these specifications may be to create a desirable look or theme in a community, sometimes the concern is actually glare or shine, which is a different topic.”
This photo shows the difference between high LRV and low LRV but with the same color. The low LRV, or matte product, is achieved by creating a micro texture in the paint, which scatters the light resulting in very little reflection. (Photo courtesy of Bluescope Coated Products)
Gloss, Sheen, Glare
Gloss and sheen are two other terms that can be used to describe the visible reflection of a surface. Gloss refers to a surface’s shininess, while sheen defines the range of gloss levels. Gloss and sheen are the measurement of concentrated visible light reflection at a specific viewing angle; 60 degrees for gloss and 85 degrees for sheen.
“Glare is controlled by the color, the lower the LRV, the lower the glare, though a high sheen can enhance a visual glare,” Edgar explains. “A high sheen (gloss) on a smooth surface can create a visual glare, where the as the same gloss on a distorted surface will create less of a visual glare. A high sheen can add depth and crispness to a color whereas flat sheen in the same color will appear more soft or pale, but the lower sheen may have a higher LRV. For glare reduction on exterior buildings, the LRV is typically 40 or less, though can be specified at 25 or under.”
While gloss is independent of color, such as black, which can have a low LRV but be very glossy, Shreve says color can be dependent on gloss with higher gloss achieving a lighter look for light colors, and a darker look for dark colors. And, high gloss coatings will have a higher LRV because more light is reflected versus the same color at a low gloss.
While there is some confusion that LRV plays a part in glare or shine, Vondran says it doesn’t. “So, if shininess is a concern, the gloss and/or sheen needs to be specified, not LRV,” she says. “Gloss and sheen are controllable through various paint formula techniques including chemical reactions, flattening additives and physical texturizing particles that create a rough or broken surface (sometimes invisible to the eye) that results in a diffusion of light and thus less glare or shine.”
Color Selection
When selecting colors, LRV is important, but Edgar notes it’s also important to remember that lighting, both natural and artificial, direct or indirect, along with the surrounding objects or environment colors are considerations that affect the appearance of a color. “LRVs are one of many elements used in architectural design criterion,” Shreve adds. “All design factors regarding color, lighting, space requirements, etc., must be used in tandem by professionals.”
As Edgar explains, different coating technologies in the same color will have a similar LRV. Comparing the same color in a matte sheen and a gloss will also have a similar LRV, though the gloss will visually reflect more light, but will have a lower LRV. “The pigments used in the paint coatings can influence the amount of heat absorbed by the color though,” he says. “Infrared (IR) pigments can reflect the heat energy away from the surface, thus creating a cooler surface temperature. The use of these pigments will have a marginal effect on lighter colors but can reduce the heat absorption up to 50% on dark colors. A dark color in the same coating, one with IR pigments and the one without, both will have a similar LRV, but the IR pigment coating will have less heat absorption, reducing the energy to cool the building, along with meeting heat island codes and glare restrictions.”
“There has been movement over the past 25 years to lower gloss paint finishes for exterior painted metal, especially in residential applications,” Vondran adds. “In recent years, more attention is being paid to low sheen and the creation of very matte finishes. Very low sheen products tend to better mimic other natural products like wood or clay, giving architects greater design options in addition to eliminating objectionable glare.”