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Stopping Solar Damage
By Loren Snyder - March 2003 - Roofing
In today’s faltering economy, maintenance and engineering managers with shrinking budgets often look for ways to minimize and defer capital costs. For managers facing tear-off and other roofing project costs, reflective roof coatings are one tool that might help stave off large capital expenditures for roofing projects.
But managers should not view coatings solely as a way to postpone reroofing projects, say coating manufacturers. Reflective coatings can pay dividends by reducing the amount or frequency of roof maintenance by protecting roof materials. Specifically, coatings help preserve roof waterproofing and can mitigate solar damage.
Before discussing the types of coatings available — and to help dispel confusion over how reflective coatings perform — a discussion of solar radiation and the damages it can cause roofing systems is necessary.
Radiation strikes the Earth in four wavelengths: X-ray, gamma, infrared (IR) and ultraviolet (UV). Of these, IR and UV radiation make it to the Earth’s surface largely unaffected by the atmosphere.
IR radiation heats the Earth. And wavelengths visible to the human eye are a narrow band of light between IR and UV frequencies. UV light, which has wavelength frequencies lower than visible light, is a disinfectant used to purify water, sterilize medical equipment, and kill mold and bacteria in HVAC ducts.
Both IR and UV radiation are necessary for life on Earth, but both also can cause significant damage to roofs.
Solar Damage Quantified
IR energy causes temperature variations that damage roofs, says Tripp Hyer, vice president of Gardner-Gibson Inc. For example, Hyer says roofs on buildings in the Southeastern United States can undergo drastic swings in temperature within relatively short time periods.
“Roofs in sunny regions can get up to 160 degrees, but when a storm comes, the rains can cool that roof to 90 degrees within minutes,” he says. “So reflective coatings can help minimize the expansion and contraction cycles that occur.” By keeping the roof surface at a cooler and constant temperature, he says, fewer roof failures will result from flashings that loosen or fasteners that pop.
Even regular daily fluctuations in temperature can damage roofing, says Paul Beemer, director of legal and technical affairs for Henry Co.
“Reducing overall roof temperature and helping prevent daily swing [in temperature] is crucial to protecting the roof membrane,” he says.
UV light, which can fade paint and break down polymers and other materials, also damages roofs. Black-bodied asphalt roofing is particularly susceptible to UV damage through a process known as actinic deterioration, says Lewis Ripps, chairman of the Palmer Asphalt Co.
“A roof unprotected by a UV coating will dry out,” he says, causing an alligatored surface.
UV radiation on uncoated roofs can oxidize the oils in asphalt, causing brittleness and a loss of aggregrates, according to manufacturers. Coatings protecting roofs against UV radiation will help prevent the roof from drying out and losing thickness.
Select types of reflective roofing also can save energy costs associated with solar heat gain. IR heat that builds up in roofing materials can allow heat to enter the occupied space of a building. This heat gain can result in higher energy costs, particularly if the structure has cooling ducts that run through the plenum or just below an uninsulated roof. To help prevent heat gain, reflective roofs also should have high emissivity — the ability of a material to give off IR heat.
“It’s important to protect against thermal shock and weathering effects, but white elastomeric coatings can also help property owners save on energy costs,” says Tony Ruffine, director of specialty products for GAF Materials Corp. While potential energy savings can be great, some manufacturers caution that using white roof coatings in certain geographical regions may not drastically reduce energy costs, though they still provide UV protection.
“You’ve got to remember that energy saving is situational,” Beemer says. “There’s much about energy savings that depends upon climate.”
For example, not every building stands to benefit from high-emissivity coatings. In northern states, solar gain might help keep a cap on winter heating bills, but buildings in the Sun Belt — particularly flat-roofed buildings with large roof area — can stand to lower summer cooling bills substantially. One study conducted by the Florida Solar Energy Center in the late 1990s showed that retail stores in a south-Florida mall reduced electric demand by up to 40 percent and cut peak cooling demand by an average of 25 percent after applying a reflective coating.
Types of Coatings
Depending upon a number of factors ranging from the presence of roof insulation to geographical location, managers should specify the reflective coating that best suits their environment and their organization’s goals and needs.
Most reflective coatings fall into one of two categories: solvent-based coatings which use varying amounts of aluminum paste to reflect solar radiation; and water-based elastomerics, which reflect a wide spectrum of radiation but generally stay cooler than aluminum-based coatings. The latter category generally includes white acrylic coatings that Hyer says have the consistency of rubbery house paint.
According to manufacturers, white elastomeric coatings stay cooler than either black asphalt roofs or aluminum-coated roofing, which means these white coatings have both higher albedo and emissivity. Silvery, aluminum-based coatings have a surface temperature somewhere between white coatings and black roofs, generally much closer to black roof temperatures on a warm day, says Ruffine.
All manufacturers agree that managers can’t simply forget about the roofs or the coating once they’ve been applied.
“Most people don’t look at the roof until it leaks,” Hyer says. Ripps agrees, and cites anecdotal evidence of the extent of one building owner’s ignorance.
“People who own roofs and make an investment in their properties need to know what’s up on their roof,” he says. “I recently visited one 400,000-square-foot building located near a trash dump. When the contractor, building owner and I got on the roof, we discovered that the roof was literally covered thick with bones that had been picked clean.” Birds apparently had carried scraps over to the building to feed, and the building owner never knew it, he says.
“Applying coatings is the easy part,” Beemer says. “Roofs are frequently dirty places, and managers should pay more attention to them.” He says the single most important task managers can schedule when using a coating is to make workers properly clean the roof before applying the coating. Managers also should implement a regular coating and rooftop inspection schedule.
“I always tell people, ‘As often as you paint the exterior, you should coat the roof,’ “ Hyer says. “Just because you can’t see the roof doesn’t mean you shouldn’t take care of it.”
Association Spotlight: RCMA
The Roof Coatings Manufacturers Association (RCMA) is the national trade association representing manufacturers of cold-applied protective roof coatings and cements, and the suppliers of products, equipment, and services to and for the industry.
RCMA was founded in 1982 by a group of industry visionaries. The association is located in downtown Washington, .,C. RCMA’s proximity to governmental and regulatory agencies and to the business organizations and many other association headquarters in the Washington, D.C., area, has proved beneficial when working in the interest of the RCMA members.
Since its founding, RCMA has grown to be a respected voice in the building-construction industry. The association has tripled its membership from some 20 member companies in 1982 to 62 member manufacturing and supplier member firms today.
In recent years, RCMA has developed strategies to effectively address the many industry challenges and opportunities facing RCMA and its members. Emphasis has been directed to government and regulatory issues, advancing product technology and education, enhanced communications and promotion, and an increased involvement with related organizations. RCMA is dedicated to serving members and directing them to resources that can help them with all phases operations.
RCMA is helping supply the roof coating needs of America. Most importantly, RCMA is dedicated to providing the RCMA member producers of cold-applied roof coatings products and systems, and cements, and the industry’s suppliers, with means to produce and provide dependable, high-quality roof coatings and cement products.
While the future of cold-process roof coatings is positive, the industry does face some challenges. For instance, increased government regulations at the federal and state levels and new performance criteria established by building code agencies make it imperative for the industry to concentrate on a unity of effort to participate in the development process. To help ensure that role in the future, RCMA is conducting cooperative activities to demonstrate product performance and promote a supply of quality, energy efficient materials that meet the needs of the consumer, as well as those of the environment.
Among the association’s benefits and activities:
RCMA has successfully evolved from its beginnings to its present day dynamics. We capitalize on the intense interest and participation of our members who insist on providing users of their products with materials that meet higher standards of performance and compliance.
Historically, cold-applied roof coatings and cements have proven time and again to be an effective and economical answer to solving many challenges associated with the installation of new roofing, as well as preventive maintenance and repair of existing roof surfaces.
To learn more about the roof coatings industry, RCMA, or any of the RCMA member companies and products, contact RCMA at (202) 207-0919, or visit the RCMA Web site.