Cool Metal Roofs
There are some significant potential benefits to specifying a cool roof on a building project. Cool roofs save building owners money by reducing ongoing operating costs, and they also have a positive effect on the environment.
Buildings consume one-third of all energy and two-thirds of all electricity generated. Cool metal roofs can help reduce energy consumption by lowering cooling loads with their wide array of finishes, designs, and colors.
Cool roof performance is a function of two radiative properties: Solar Reflectance and Infrared Emittance.
Solar reflectance is defined by the Cool Roof Rating Council (CRRC) as, "The ratio of the reflected flux to the incident flux". In other words, the number reported for solar reflectance for a roof product is a decimal number less than one that represents the fraction of light reflected off the roof. For example: "high" reflectance materials, such as white painted metal roofing, have values of around 0.70 (a.k.a. 70%). That is, only 30% of the light from the sun is retained by the roof.
Infrared emittance is defined by CRRC as, "The ratio of the radiant heat flux emitted by a sample to that emitted by a black body radiator at the same temperature". In plain terms, emittance is a decimal number less than one that represents the fraction of heat that is re-radiated from a material to its surroundings.
Cool metal roofing will last for decades without color fading, and the surface of metal roofs is resilient and resists dirt and biological build-up, which keeps them cool longer than other roof types where soil and algae can form. Metal roofing also has a low life-cycle cost due to its longevity compared to other roof types.
You can find more information on the benefits of cool metal roofing by visiting the Cool Metal Roofing Coalition (CMRC) website: www.coolmetalroofing.org.