Cool roof

Reflective surfaces are surfaces that can deliver high solar reflectance (the ability to reflect the visible, infrared and ultraviolet wavelengths of the sun, reducing heat transfer to the surface) and high thermal emittance (the ability to radiate absorbed, or non-reflected solar energy). Reflective surfaces are a form of geoengineering.

The most well-known type of reflective surface is the cool roof. While cool roofs are mostly associated with white roofs, they come in a variety of colors and materials and are available for both commercial and residential buildings. Today's "cool roof" pigments allow metal roofing products to be EnergyStar rated in dark colors, even black.

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 decreasing the need for air conditioning, fuel consumption, and emissions of greenhouse gases and urban air pollutants.

Cool color parking lots are parking lots made with a reflective layer of paint. The project is being undertaken by Jordan Woods of the Berkeley Lab.

Cool roofs, in hotter climates, can offer both immediate and long-term benefits including:

Cool roofs achieve cooling energy savings in hot summers but can increase heating energy load during cold winters. Therefore, the net energy saving of cool roofs varies depending on climate. However, a 2010 energy efficiency study looking at this issue for air-conditioned commercial buildings across the United States found that the summer cooling savings typically outweigh the winter heating penalty even in cold climates near the Canada–US border giving savings in both electricity and emissions. Without a proper maintenance program to keep the material clean, the energy savings of cool roofs can diminish over time due to albedo degradation and soiling.

Research and practical experience with the degradation of roofing membranes over a number of years have shown that heat from the sun is one of the most potent factors that affects durability. High temperatures and large variations, seasonally or daily, at the roofing level are detrimental to the longevity of roof membranes. Reducing the extremes of temperature change will reduce the incidence of damage to membrane systems. Covering membranes with materials that reflect ultraviolet and infrared radiation will reduce damage caused by u/v and heat degradation. White surfaces reflect more than half of the radiation that reaches them, while black surfaces absorb almost all. White or white coated roofing membranes, or white gravel cover would appear to be the best approach to control these problems where membranes must be left exposed to solar radiation.

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Wikipedia