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Cool RoofsMarch 22nd, 2012 by
With energy costs zapping more and more of homeowners’ budgets, many are looking for ways to reduce their electricity usage.
Some of the more popular strategies include unplugging idle electronic devices, turning the thermostat down a few degrees, and purchasing ENERGY STAR-rated appliances. However, there is also a less well-known part of the home that can produce energy savings: the roof.
What Are Cool Roofs?
Because of the large amount of electricity used by air conditioning, many homeowners are investigating cool roofs, so called because their surface is designed to stay cool by reflecting and emitting as much of the sun’s energy as possible.
This minimizes the amount of heat transferred into the home through the roof, thus reducing the air conditioning system’s workload. Cool roofs accomplish this through a combination of their color and composition.
Because light colors reflect more energy than dark colors, many cool roofs are white or very light gray. While color plays a significant role in keeping cool roofs cool, most cool roofs are also coated with a highly solar-reflective material that aids in bouncing back the sun’s energy.
High Thermal Emissivity
Besides solar reflectivity, cool roofs also have high thermal emissivity. This refers to the ability of materials to radiate the absorbed heat that isn’t immediately reflected. Think about a piece of paper and a wrench both left in the sun.
The paper, which has high thermal emissivity, won’t retain much of the sun’s energy and its temperature will remain relatively static.
The wrench, on the other hand, has very low thermal emissivity and will trap most of the energy it absorbs, causing it to get hotter. Most cool roofs can emit 90 percent or more of their absorbed heat.
Benefits of Cool Roofing Products
According to ENERGY STAR, ENERGY STAR-rated cool roofing products can reduce a roof’s surface temperature by as much as 100 degrees and reduce a home’s peak cooling demand by 15 percent.
Cool roofs also last longer than regular roofs because they don’t expand and contract with the heat as much as regular roofs.
Finally, cool roofs are better for the environment than regular roofs, since they ease energy consumption and mitigate the problem of urban heat islands, which can be a health concern for residents.
While cool roofs will slightly increase a home’s heating bill during the winter, that extra cost is more than offset by the amount saved during the summer, especially in a climate like Atlanta’s. There are two primary reasons for this:
First, the winter sun is lower in the sky and less intense than in the summer, so the vast majority of passive solar heating occurs through the home’s windows during this time. Second, there are fewer hours of sunshine during the winter due to shorter and frequently cloudy days.
For a climate like Atlanta’s, cool roofs are an excellent way to reduce your energy bills, increase the longevity of your roof, and help reduce the urban heat island that “Hotlanta” can become.