Raising roof reflectivity from an existing 10-20% to about 60% can reduce cooling-energy use in buildings in excess of 20%. Cool roofs also result in a lower ambient temperature that further decreases the need for air conditioning and retards smog formation. In 2002, suitable cool white materials were available for most roof products, with the notable exception of asphalt shingles; cooler colored materials are needed for all types of roofing. To help to fill this gap, the California Energy Commission (Energy Commission) engaged Lawrence Berkeley National Laboratory (LBNL) and Oak Ridge National Laboratory (ORNL) to work on a three-year project with the roofing industry to develop and produce reflective, colored roofing products. The intended outcome of this project was to make cool-colored roofing materials a market reality within three to five years. For residential shingles, we have developed prototype light-colored shingles with solar reflectances of up to 35%. One manufacturer currently markets colored shingles with the ENERGY STAR qualifying solar reflectance of 0.25. Colored metal and clay tile roofing materials with solar reflectances of 0.30 to 0.60 are currently available in theCalifornia market.
LBNL and ORNL performed research & development in conjunction with pigment manufacturers, and worked with roofing materials manufacturers to reduce the sunlit temperatures of nonwhite asphalt shingles, clay tiles, concrete tiles, metal products, and wood shakes. A significant portion of the effort was devoted to identification and characterization of pigments to include and exclude in cool coating systems, and to the development of engineering methods for effective and economic incorporation of cool pigments in roofing materials. The project also measured and documented the laboratory and in-situ performances of roofing products. We also established and monitored three pairs of demonstration homes to measure and showcase the energy-saving benefits of cool roofs. The following activities were carried out.
In collaboration with the Energy Commission, we convened a Project Advisory Committee (PAC), composed of 15 to 20 diverse professionals, to provide strategic guidance to the project.
In order to determine how to optimize the solar reflectance of a pigmented coating matching a particular color, and how the performance of cool-colored roofing products compares to that of a standard material, we (1) measured and characterized the optical properties of many standard and innovative pigmentation materials; (2) developed a computer model to maximize the solar reflectance of roofing materials for a choice of visible colors; and (3) created a database ofcharacteristics of cool pigments.
In order to help manufacturers design innovative methods to produce cool-colored roofing materials, we (1) compiled information on roofing materials manufacturing methods; (2) worked with roofing manufacturers to design innovative production methods for cool-colored materials; and (3) tested the performance of materials in weather-testing facilities.
One of the project objectives was to demonstrate, measure and document the building energy savings, improved durability and sustainability attained by use of cool-colored roof materials to key stakeholders (consumers, roofing manufacturers, roofing contractors, and retail home improvement centers). In order to do this, we (1) monitored buildings at California demonstration sites to measure and document the energy savings of cool-colored roof materials; (2) conducted materials testing at weathering farms in California; (3) conducted thermal testing at the ORNL Steep-slope Assembly Testing Facility; and (4) performed a detailed study toinvestigate the effect of solar reflectance on product useful life.
We developed partnerships with various members of the roofing industry. We worked through the trade associations to communicate and advertise to their membership new cool color roof technology and products. This collaboration induced the manufacturers to develop a market plan for Ca ifornia and to provide technical input and support for this activity. Through the industry partners, many California housing developers and contractors have been convinced to install the new cool-colored roofing products.