Posted on March 7, 2016
Color and Beyond
Most people have a basic understanding how solar reflection works. You know that if you wear a black t-shirt on a hot summer day you will feel significantly warmer than if you wear a white t-shirt and you likely know this is due to the fact that white reflects more of the sun’s rays while black absorbs them, drawing them toward your body. The same principle is true for homes. According to the National Renewable Energy Laboratory:
The primary source of heat buildup (i.e., gain) is sunlight absorbed by your house through the roof, walls, and windows. Dull, dark-colored home exteriors absorb 70% to 90% of the radiant energy from the sun that strikes the home’s surfaces. Some of this absorbed energy is then transferred into your home by way of conduction, resulting in heat gain. In contrast, light-colored surfaces effectively reflect most of the heat away from your home.2
The effect of switching from a dark-colored to a light-colored home exterior can be significant. One study on Florida homes found that increasing heat reflectivity through the use of light colors saved homeowners an “an average of 23% of their cooling costs” and widespread implementation of such measures could incur a nationwide savings of “$10 billion in energy and equipment costs.”3 But while color itself can be an important part of heat absorption, what ultimately matters is solar reflectance, which, thanks to recent advances in paints and coatings, no longer necessarily correlates with color.
Expanding the Possibilities of Passive Cooling
Many homeowners have a specific vision for what they want their home to look like. As such, while they may know that a light-colored home with a light-colored or reflective metal roof is the best option for maximizing solar reflection, they may be reluctant to take such measures due to aesthetic or practical concerns. The paints and coatings industry recognizes this and has begun to expand the appeal of passive cooling by developing products that minimize light absorption on even dark surfaces.
Today, these products take the form of everything from solar reflective paints with built-in light reflection properties to specialized coatings to minimize light absorption, including 3M Glass Bubbles that use a hollow structure with a low refractive index to maximize solar reflection, titanium dioxide compound integration, and proprietary pigments that “reflect energy in the near and far infrared region of the spectrum even though they absorb strongly in the visible region.” 4 With an ever-growing number of solar reflective paint and coating options to choose from, these innovative products can be applied to a full range of traditional and modern wall and roofing materials, including wood, metal, polymers, and concrete, and allows homeowners to optimize cooling without compromising appearance.
Measuring Color in Solar Reflective Paint
Evaluating the efficacy of light reflecting products requires the use of advanced spectral technologies to quantify total solar reflection values (TSR). Spectrophotometric instrumentation offers the most accurate and cost-effective way of determining reflectance values of all sample types and can evaluate individual ingredients, complete formulations, and installed products. For manufacturers, detailed TSR analysis is critical to measuring the success of a product, facilitating the tailoring of formulations, and continuously monitoring product efficacy during production. Additionally, employing spectral analysis during product testing allows you to observe the performance of the product over time by measuring TSR in response to environmental stressors and establishing durability of protection. For consumers, both initial and eventual TSR values are vital to ensuring they can make informed choices regarding building materials and have the Solar Reflectance Index (SRI) data needed to for LEED certification.5
But spectrophotometers don’t only provide you with TSR data; they are also essential to evaluating color. The range of optical geometries available in modern spectrophotometers allows you to precisely and easily capture color information at any point in your product design or manufacturing process ensure that you can consistently produce the shades needed to meet the needs of consumers. Colorimetric analysis of light reflecting coatings is particularly important to determine what effect, if any, they have on underlying materials and protect against unwanted color shifts.
Full article with photos available here: