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What Makes a “Cool Roof” Energy Efficient?April 24th, 2014 by
A cool roof is just what it sounds like—a roof that maintains a lower temperature than traditional roofs. Its coolness is not restricted to just temperature, though; it is also a cool option for both homes and commercial buildings because it is environmentally friendly and cost effective.
How Cool Roofs Work
The surface color and material of a cool roof are what determine its coolness. There are two facets of the cooling process that can work independently or in conjunction with one another: light reflection and heat absorption. Some heat transfer into the building will inevitably occur, but roofs that effectively reflect sunlight and emit thermal radiation will be much cooler than roofs that have no defenses against absorbing light and heat from the sun.
Metal roofs are naturally the best at reflecting sunlight, but almost any type of roof can be adjusted to improve reflectivity and thermal emission by an addition of a special, paint-like coating. White coats are ideal for reflecting light, but if color is desired for aesthetic purposes, cool-toned color coats also offer some light-reflecting capabilities. Reflective granules can even be added to darker color coats to achieve some reflectivity improvement.
The Advantages of Installing a Cool Roof
The positive ramifications of a cool roof installation are significant. In addition to doing your eco-friendly part by opting for a cool roof, you will also be saving money and possibly prolonging the life of your roof.
Environmental benefits. If many buildings or houses in an area install cool roofs, it helps fight against the “urban heat island” effect, which occurs when too many dark roofs in a cluster heat the air above them and radiate heat into the atmosphere. Researchers say that limiting this effect will slow global warming and hinder smog production since smog thrives in warm air. A lower air temperature around roofs results in cooler climates and a decrease in Earth’s surface temperature.
Homeowner benefits. Because cool roofs allow homes and buildings to absorb less heat, A/C systems do not require as much usage, which cuts down on energy bills as well as A/C repair and maintenance costs. If A/C systems are used less, then electrical grids will experience less strain and are less likely to have power outages that disrupt everyday life. A cool roof coating may even extend roof life by protecting against heat damage that can wear down your roof over time. Additionally, a tax credit is often awarded to homeowners and businesses that install cool roofs. According to ENERGY STAR, the credit is usually either 10 percent of the cost of the roof up to $500 (not including installation) or a specific amount between $50 and $300.
Will a Cool Roof Work for Everyone?
Cool roofs are priced roughly the same as traditional roofs, so if you are in the market for a new roof, they are definitely worth considering. Some are marginally more expensive than regular roofs, but the money saved in energy bills after installation will often quickly make up for the extra up-front cost.
It is important to note that cool roofs are most energy efficient in hot, dry climates. If you live in an area that is predominately overcast, rainy, or cold, cool roofs will not provide the same returns as they would in hotter regions. While cooling bills will decrease, heating bills will likely be slightly higher because of a smaller heat transfer into the house from the roof.
The few weaknesses of cool roofs are easily outweighed by the copious ecological and personal advantages they provide. If cool roofs achieve widespread use, the Earth could become a much healthier, more comfortable place.
Sources: ENERGY STAR; EPA; Heat Island Group; US Department of Energy.
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