Reflective Vinyl Roofs Save Energy

Faced with rising energy costs, smart building managers are discovering that light-colored roofs made of vinyl offer a unique solution. Scientists have found that reflective surfaces on top of buildings can play a critical role in cutting energy consumption inside them.

Recent studies show that temperatures are significantly lower in areas with more vegetation and light-colored, reflective surfaces than in urban "heat islands" caused by acres of dark, asphalt parking lots and black roofs. In fact, scientists have found that the air in "urban heat islands" can be as much as 6 to 8 degrees hotter than in surrounding areas.

It’s a simple concept - reduce utility costs by reducing the temperature of the roofing surface, thereby reducing the temperature of the interior of the building. The warmer the climate, the greater the savings. When the temperature outdoors reaches 90° F, the temperature on a black roof can be as high as 160° F, according to The Heat Island Group at the University of California, Berkeley. Some of that heat is transferred inside to the occupants of the building, resulting in higher utility costs for air conditioning to keep the occupants comfortable.

Additional studies by the Florida Solar Energy Center and the U.S. Environmental Protection Agency (EPA) confirm that reflective roofs made of polyvinyl chloride (PVC or vinyl) membranes or other single-ply materials can reduce utility costs of air-conditioning by as much as 50 percent. And cooling demand in the peak hours - the most costly - can be reduced by 10 to 15 percent, reducing demand on the grid. According to the EPA, $40 billion is spent annually in the United States to air condition buildings - about one-sixth of all electricity generated in the United States each year.

In a recent study sponsored by the EPA and the U.S. Department of Energy (DOE), scientists at the Lawrence Berkeley National Laboratory measured and documented summertime air-conditioning energy savings and power demand reduction from a large retail store in Austin, Texas. The store was retrofitted with a reflective vinyl roof membrane manufactured by Sarnafil, Inc. Temperatures were monitored with the original black rubber roofing membrane from August 1999 to April 2000. In April and May 2000, the roof was replaced with a white thermoplastic membrane, and monitoring continued from late May through the summer of 2000.

The results were significant. The average daily summertime temperature on the surface of the black roof was 168° F, but only 125° F on the white vinyl roof. Measured at the plenum between the roof and the ceiling, average temperatures were reduced from 101° F to 95° F.

Scientists concluded that installation of the white vinyl roof would save the building’s owners about 63 megawatt hours of energy consumption per year, with annual energy- and peak-demand savings of about $7,200. They conservatively extrapolated this over a 13-year expected life for the roof and concluded that the present value of future energy savings would range from $62,000 to $71,000. (In fact, according to the manufacturer, Sarnafil’s vinyl roofs have demonstrated a service life capability in excess of 30 years, so the savings should be substantially higher.)

In addition, according to the building manager, lower labor costs offset higher material costs when installing a white thermoplastic roof instead of a black rubber roof, yielding a negligible cost differential. Therefore, the payback for this system was immediate.

Scientists point out that that the magnitude of energy savings will vary depending upon the building type, level of roof insulation, ventilation rate between roof and ceiling, size and efficiency of the air-conditioning system and, of course, roof solar reflectance.

But it’s clear that white vinyl roofing membranes can offer substantial savings for retail stores, sports arenas, schools, manufacturing facilities, office buildings and hospitals with large roof surfaces and low-slope roofs. Jim Poltl, director of maintenance and operations for the San Marcos Unified School District in San Marcos, Calif., has installed reflective vinyl roofs on several projects and is now covering 30,000 square feet at three school sites with these roofs.

"The money saved on energy costs is really the icing on the cake," Poltl says. "This is an excellent design and a good system." His district of about 12,000 pupils started the retrofitting project because the old roofs on single-story manufactured classrooms were leaking. However, once the new system was installed - complete with improved insulation - he started hearing comments from teachers who noticed how much cooler and quieter their rooms were.

The U.S. Environmental Protection Agency (EPA) maintains a list of ENERGY STAR^® Roofing Products that meet these criteria. The EPA’s Energy Star program promotes the use of reflective roofing materials, and lists some 115 manufacturers of energy-saving membranes. To qualify, products must have a total initial solar reflectivity of at least 0.65 - meaning that 65 percent of all solar energy is reflected away from the surface, and only 35 percent absorbed. EPA has recognized certain vinyl roofing manufacturers as Charter Partners of their Energy Star Roof Product Program for their commitment to develop specific products that meet agreed-upon energy-efficient criteria.

As an added benefit, research has demonstrated that lowering the temperature in urban areas can actually reduce smog.

Of course, as Poltl points out, the primary function of a roof is to shelter the building from the elements. Reinforced thermoplastic vinyl roofing membranes do an excellent job of this as well, withstanding wear and tear and the toughest weather conditions while remaining watertight.

The advent of single-ply roofing technologies in the United States came in the mid-1960s, with vinyl membranes arriving shortly thereafter in the early 1970s. The concept was attractive to roofing contractors and building owners, because single-ply technologies offered a clean, safe, energy-efficient and cost-effective alternative to built-up roofs, as well as greater design flexibility with slopes and roofing aesthetics.

While most vinyl roofs are white, gray or tan - perfect colors to reflect heat - vinyl membranes also offer color versatility, enabling designers to incorporate patterns, logos or a variety of colors into the vinyl roofing membranes. Vinyl membranes are designed to repel dirt, maintaining aesthetic appeal and maximizing reflectivity.

Vinyl roofing membranes can be designed to resist wind uplift, structural movement and harsh outdoor elements. In addition, vinyl roofing membranes have a documented performance track record that exceeds 30 years, and are inherently fire resistant, exceeding current standards and providing an extra measure of safety over the alternatives.

Finally, vinyl roofing membranes can also be found as a component in "green roofs," which consist of a multi-layer soil and drainage system upon which vegetation can grow on urban roofs. Green roofs, in turn, improve the energy efficiency of buildings, enhance the look of urban rooftops and promote healthier air in such areas.

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Dunne Roofing Company

310 Busse Highway #271

Park Ridge, IL 60068