Energy-efficient Roofs Can Save
by Greg Guy
Is your roof cool?
Traditionally, roofs of manufacturing facilities or warehouses have been built strictly by a simple formula: cost of construction versus years of service. If you spend more, you expect the roof to last longer. Little thought was given to how that roof affected the internal temperature of the building.
That is changing. A practice that is spreading nationwide is adding another component to your roofing choices -- energy efficient materials. The reason is obvious: the more efficient your roof, the lower your air conditioning costs.
Higher temperatures in buildings have a direct effect on worker productivity as well as comfort.
A joint study last year between Helsinki University and Berkeley National Laboratory in Berkeley, Calif., noted that the indoor temperature affected several human responses, including thermal comfort, perceived air quality, symptoms of sick building syndrome and work performance. For every 1 degree Celsius rise in temperature above 25 degrees (77 degrees Fahrenheit), worker productivity dropped more than 2 percent, the study showed.
Factory owners must take into account loss of productivity when determining what type of roof to build, as well as the cost of air conditioning or other cooling method. It's also a competitive advantage for businesses to consider.
In order to attract the best workers, a business must allow its people to work in comfort. If owners can achieve this goal without expensive air conditioning, it puts them ahead of their competitors.
Black roofs can become up to 70 percent hotter than white ones, as measured by the Solar Reflective Index (SRI). Dramatic savings in HVAC (heating ventilation and air conditioning) costs have alerted businesses to the trend toward more efficient roofs. Simply by using a light-colored material, such as white latex or aluminum, you can reflect the heat, thus lowering air conditioning costs by up to 40 percent.
Businesses could save between one and five cents per square foot of building space per year -- and an additional three cents to five cents more during periods of peak demands, reports Dave Roodvoets, technical director for Spry Products in Ohio and a board member for the Cool Roof Rating Council.
If you're operating a large manufacturing facility, by installing a high-SRI roof, you could be saving at least $10,000 per year in energy costs, as some agencies and utility districts throughout the country are beginning to sponsor rebate programs in order to encourage more businesses to build efficient roofs or to upgrade when a roof replacement becomes necessary. The savings can help the utilities better manage peak demand loads.
However, even cool roofs will lose some of their SRI over time, as dirt and weathering occur. Owners must have a regular program of maintenance and washing in order to maintain a high degree of reflectivity.
Another way to cut air conditioning costs is to use water cooling. By wetting down a roof or providing misting sprays, you can lower the internal temperature by several degrees. The water would have to be readily available and could be circulated through a pond on the grounds to keep costs down.
But the savings can make the effort worthwhile, especially during hot days when electric demand peaks and businesses pay a premium to operate equipment.
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