represents total reflectivity. Thermal emittance is the ability to emit absorbed heat. It is also expressed either as a decimal fraction between 0 and 1, or a percentage. Another method of evaluating coolness is the solar reflectance index (SRI), which incorporates both solar reflectance and emittance in a single value. SRI measures the roof's ability to reject solar heat, defined such that a standard black (reflectance 0.05, emittance 0.90) is 0 and a standard white (reflectance 0.80, emittance 0.90) is 100. A perfect SRI is approximately 122, the value for a perfect mirror, which absorbs no sunlight and has very low emissivity. The only practical material which approaches this level is stainless steel with an SRI of 112. High-reflectivity, low-emissivity roofs maintain a temperature very close to ambient at all times preventing heat gains in hot climates and minimizing heat loss in cold climates. High emissivity roofs have much higher heat loss in cold climates for the same insulation values. Roof Savings Calculator The Roof Savings Calculator (RSC) is a tool developed by the U.S. Department of Energy's Oak Ridge National Laboratory which estimates cooling and heating savings for low-slope roof applications with white and black surfaces. This tool was the collaboration of both Oak Ridge National Laboratory and Lawrence Berkeley National Laboratory in order to provide industry-consensus roof savings for both residential and commercial buildings. It reports the net annual energy savings (cooling energy savings minus heating penalties) and thus is only applicable to the buildings with a heating and/or cooling system. Cars Solar reflective cars or cool cars reflect more sunlight than dark cars, reducing the amount of heat that is transmitted into the car's interior. Therefore, it helps decrease the need for air conditioning, fuel consumption, and emissions of greenhouse gases and urban air pollutants. Cool pavements Cool color parking lots are parking lots made with a reflective layer of paint. Cool pavements which are designed to reflect solar radiation may use modified mixes, reflective coatings, permeable pavements, and vegetated pavements. Mirrors Mirrors are being explored as a reflective surface to reflect solar radiation and cool temperatures. MEER is a nonprofit using recycled materials to manufacture mirrors and polymer reflective films for potential widespread use on rooftops and in open spaces such as farmland. Trials have been undertaken in California and further application opportunities are developing in New Hampshire, India, and Africa. Climatic variables Cool roofs In