A cool reflective roof is a roofing system that can deliver high solar reflectance (also know as albedo). As a general rule, cool reflective roofs also deliver high levels of thermal emittance in order to qualify under current cool roofing standards.
Although the majority of reflective roofs installed today are white in color, advanced work in infrared (IR) reflective pigments has allowed the development of cool reflective roofs in colors other than white. Several informative articles about the development and application of IR-reflective coatings include:
Many elastomeric roofing membranes are available in cool reflective formulations. Although the surface layer of such membranes is formulated to be inherently reflective, almost all cool membranes are produced as composites, with an upper layer of inherently reflective membrane and a lower layer or layers of non-reflective materials. Examples of cool roofing membranes include:
*Although many EPDM membranes used in commercial roofing are black in color and are not classified as cool reflective roof membranes, white reflective versions of EPDM are commercially available that meet or exceed current reflectiive roof membrane standards.
Additional information about cool roof membranes is available from a variety of sources, including the Vinyl Roofing Division of the Chemical Fabrics and Film Association, the EPDM Roofing Association, the Asphalt Roofing Manufacturers Association, and the Single-Ply Roofing Institute. Product listings for cool roof membranes that meet or exceed current cool reflective roof standards are available from the Cool Roof Rating Council and the EPA ENERGY STAR reflective roofing program.
A wide variety of cool reflective roof coatings are available that may be used to apply a reflective surface on both new and existing roofing membranes. In addition, some roofing products are available with factory-applied cool coatings. Examples of popular cool roof coatings include:
Additional information about cool roof coatings is available from the White Coatings Council of the Roof Coatings Manufacturers Association and the Reflective Roof Coatings Institute. Product listings for cool roof coatings that meet or exceed current cool reflective roof standards are available from the Cool Roof Rating Council and the EPA ENERGY STAR reflective roofing program.
Cool metal roofing comprises a family of roofing products featuring metal surfaces that may be unpainted, pre-painted, or granular-coated. Cool metal roofs are available in a wide variety of finishes, colors, textures, and profiles for both steep-slope and low-slope applications. Additional information about cool metal roofs is available from the Cool Metal Roofing Coalition. Product listings for cool metal roofs that meet or exceed current cool reflective roof standards are available from the Cool Roof Rating Council and the EPA ENERGY STAR reflective roofing program.
Revised formulations of ceramic granules used as a surfacing on asphalt roofing shingles been developed that can meet or exceed current roof reflectivity standards for steep-slope roofing applications. Additional information about cool roof shingles is available from the Cool Colors Project jointly sponsored by Lawrence Berkeley and Oak Ridge National Laboratories. Product listings for cool shingles that meet or exceed current cool reflective roof standards are available from the Cool Roof Rating Council and the EPA ENERGY STAR reflective roofing program.
Research conducted by Dr. William Miller of Oak Ridge National Laboratory (“Steep-Slope Assembly Testing of Clay and Concrete Tile with and without Cool Pigmented Colors”) indicates certain clay tiles can meet or exceed current standards for cool reflective roofing. Dr. Miller’s research also indicates that clay tiles reduce solar heat transfer due to the thermal mass of the clay tile and convection in the ventilating space between the clay time and the roof deck. . This natural ventilation translates into cooler attic temperatures in the summer and warmer temperatures in the winter. According to Dr. Miller, “The clay roof tile showed up to 70% heat reduction entering the house as compared to roofs with (non-reflective) shingles.”
Additional information about cool clay tile roofs is available from the Tile Roofing Institute. Product listings for cool tile roofs that meet or exceed current cool reflective roof standards are available from the Cool Roof Rating Council and the EPA ENERGY STAR reflective roofing program.