Roof Coatings Protect and Reflect
August 2004 - Paints & Coatings
Report prepared on behalf of Roof Coatings Manufacturers Association
One constant in facilities management is that there never seems to be enough money for needed im-provements and maintenance.
That’s true despite the fact that a comprehensive maintenance program is perhaps the best way to protect an organization’s facilities. And when it comes to adequate maintenance, roofing is one of the most overlooked spots — out of sight, out of mind, as the expression goes. Occupants make it known when lamps burn out above their desks or when a conference room is frigid. But unless there are water spots on the ceiling tiles — or drops falling on heads — roofs go unnoticed.
They shouldn’t. Perhaps more than any other feature, roofing protects an organization’s assets. And if the capital budget needs to be protected, roof coatings can help extend the life of a roof, allowing facilities executives to defer the capital costs of reroofing and the expensive business disruption it can cause.
Even for roofs with many years of service left, coatings can help protect the original roof from further ultraviolet (UV) and infrared heat degradation. The heat shock that accompanies diurnal swings in temperatures has a debilitating effect on watertight seals, flashings, rubber roofing and asphalt. Coatings that reflect the sun’s UV rays and infrared radiation reduce absorbed heat and prolong roofing life.
Coatings that reflect heat can also help protect against another kind of shock — the one from opening the monthly energy bill. Particularly for flat-roofed or low-sloped buildings with air-conditioning ducts that run through the plenum, roof coatings can substantially reduce summertime cooling costs; that’s all the more true if the plenum space is uninsulated. One study by the Florida Solar Energy Center indicates that cool roofs — those that reflect the sun’s rays — can reduce energy costs for large buildings with moderate insulation by 10 to 20 percent.
But to use roof coatings successfully, it’s critical that facilities managers understand the situations best suited for coating applications.
Two situations are common reasons to apply a coating:
- To maximize roof life and minimize energy bills with a roof that reflects harmful ultraviolet light and infrared rays.
- To make a mid-life roof watertight and maintainable.
- Though less common, other situations might warrant the use of coatings as well:
- Reflective coatings applied when the roof was installed require periodic re-coating to restore the reflective properties and prolong the life of the roof.
- Coatings also can serve cosmetic purposes. For facilities with roofs exposed to common view — beneath a highway overpass, or next to high-rise structures, for example — coatings can improve roof aesthetics.
- Certain coatings also can retard flame spread. These UL-listed coatings are typically specified with the roof installation, though they can be applied later.
But for all they’re capable of, coatings should not be viewed as a cure-all for roof ailments.
Steve Hudak, president of KST Coatings Manufacturing Inc., has met with people who expect coatings to do too much. “If the roof is not structurally sound, it will have to be replaced,” he says. “You can’t just put a coating up and expect miracles.”
Though coatings are versatile, they’re not appropriate in every instance. In some cases, roofs are significantly deteriorated, and the only viable and cost-effective option is a comprehensive tear-off and reroof. “It’s important to remember that – as much as some people would like such a product – there is no one thing that does everything,” says Paul Beemer, director of legal and technical affairs for Henry Co.
Tim Nelligan, president of United Cool Roof Coatings, expresses a similar view. “Facilities managers cannot think of a coating as solving all their roofing problems,” he says. “If you have a leak, fix it before you apply a coating. Sure, a coating will probably stop the leak, but that fix won’t last as long as if you fix the leak and then apply the coating.”
Types of Coatings
Beemer divides coatings into three broad categories: traditional, reflective and maintenance.
Traditional coatings rely on basic materials that have been used for decades and are designed to be chemically compatible with the existing roof. By protecting the roof from direct exposure to UV light, water and other weather elements, coatings extend the life of the roof. They also serve a secondary purpose of sealing minor imperfections in the roof. Traditional coatings include coal-tar, asphalt emulsions and solvent-based asphalt applications.
Because traditional coatings are relatively easy to apply and frequently do not require specialized knowledge or equipment, facilities managers can often use an organization’s facility personnel to apply these types of coatings to low-slope and flat roofs. Those applying the coating, though, should heed manufacturers’ labels regarding ambient temperature during application, necessary curing times, roof surface preparations and other factors.
Reflective coatings also protect the roof from exposure to sunlight and weather processes, but with the added benefit of reflecting infrared heat. Beemer says that even modest reductions in roof temperature can significantly extend roof life.
“This is particularly true for well-insulated roof systems, which tend to be hotter because they cannot shed heat into the building,” Beemer says. “Well-insulated black roofs are generally seen to have a shorter life than the identical system placed over lower insulation.”
Reflective coatings come in two predominant types: water-based white acrylic roof coatings and reflective aluminum asphalt coatings.
Acrylic coatings reduce infrared heat absorption in the roof membrane. These elastomeric coatings help reduce the internal temperature of uninsulated buildings, saving cooling costs. Because they generally contain low VOCs, water-based coatings are more environmentally acceptable than solvent-based coatings and last as long as other coatings, according to Nelligan.
Water-based white acrylics must be selected carefully. For example, to use a white coating on an asphalt roof, facilities managers must specify a coating formulated for asphalt.
More so than other coatings, water-based white acrylics are not intended for use in standing water. If a roof has a tendency to pond, maintenance staff should first fill the depressions where ponded water accumulates before applying an acrylic coating. Their application also is limited to emulsion surfaces, and they should not be applied at temperatures below 45 degrees. For a gravel roof, the recommendations of the manufacturer should be followed. Finally, the curing time should not be underestimated: Water-based coatings can require from six to 48 hours of cure time before the roof can be exposed to rain or cold temperatures. It’s crucial that the instructions on the label are followed.
Reflective aluminum-asphalt coatings use aluminum flakes in an asphalt matrix. While they retain slightly more infrared heat than white coatings, they can be applied on a variety of substrates, including metal, single-ply and built-up roofs. Either type of coating can be used on unpainted metal roofs, but only the aluminum-asphalt roof coatings will allow the roof to retain a metallic appearance.
Maintenance membranes use a combination of coating and reinforcing fabric. The membranes are used either as a short-term effort to stabilize a roof that might be compromised and eventually will need to be replaced, or as a longer-term solution that can extend the life of the roof five to 15 years. Beemer is careful to note that simply applying coatings is not the same as applying a complete maintenance system.
Knowing which coating is best depends on a host of factors, say manufacturers.
“People concerned most with longevity generally choose white coatings,” says Beemer. “But many things can affect how facilities managers choose their roofing materials. Some are concerned with a LEED rating, and others are more concerned with energy savings. Almost all care about their bottom line, so longevity factors into that decision.”
“My company sees much greater use of bituminous-based reflective coatings versus elastomeric coatings,” says Van Ripps, president of Palmer Asphalt. “Facilities managers in colder geographic areas have concerns for energy costs related to both heating and cooling. Reflective bituminous coatings, specifically aluminum-pigmented coatings, reflect heat and the UV rays of the sun and do retain some heat, plus I think that facilities managers and contractors are comfortable with their use.”
Nevertheless, Ripps also sees many specifiers who prefer elastomeric coatings.
“Elastomeric coatings are new, so specifiers need to keep current with product knowledge and trends,” he says.
Hudak of KST Coatings says that bituminous coatings seem to be the specifiers’ coating of choice. “Particularly if you’ve got thousands of square feet, bituminous is just more cost-effective on the initial application, although that’s not necessarily the case when you calculate the life cycle cost,” he says.
Geography also matters when choosing coatings. Obviously, facilities in the Sun Belt will expect greater benefits from reflective roofing than facilities in the Snow Belt or the rainy Northwest.
Pitfalls to Avoid
Roofs are expensive, and even coatings — which cost much less than a reroofing job — represent an investment that is expected to pay off in benefits to the organization. That is why it’s imperative for facilities managers to make sure the coating is applied properly.
For facilities managers who are planning on having their newly constructed roof coated, Kurt Sosinski, product manager at Tremco Inc., suggests bidding the roof coating separately.
“Because of the roofing calendar, your new roof may not be completed until sometime in the fall, and I would advise against applying a water-based acrylic roof coating late in the year,” he says. “Even though they may appear dry initially, shorter days and cooler nights will slow the ultimate cure of these types of coatings. Rain, dew and small amounts of standing water can delaminate an uncured coating.”
“You’re just as well to wait until early summer the next year to apply the water-based coating. That way, the coating has much better conditions to cure — those first 30 days are critical.”
Hudak says he’s been on buildings for inspections and has seen coatings applied without any roof preparation whatsoever. “These guys had coated right over leaves and twigs,” he says.
This situation is one that gives coating manufacturers nightmares: lack of roof preparation, even cleaning it of debris like leaves and dirt. “Failure to adequately prepare the roof is the biggest sin,” says Beemer.
Preparing the roof is vital to coating success for one principal reason: Coatings must bond with the roof.
Hudak also says that another pitfall to avoid is related to the topic of preparation and adhesion. “Specifiers need to be careful not to get hung up on just one aspect of coatings,” he says. “Look at other factors and weigh all considerations. There are times when a water-based coating would be nice, but above all else you’ve got to make sure that the coating is compatible with the substrate.”
Sometimes, Hudak says, solvent-based coatings are necessary to obtain the proper adhesion on substrates.
Heed the Label
Manufacturers also caution facilities managers to read and understand the directions on the product labels. Along with over- or under-application of the product, Ripps says he has seen products used on surfaces for which they are not intended.
Sometimes, not heeding a manufacturer’s labels can have dire consequences. In one case, a prison applied a solvent-based coating on its roof, but maintenance staff had neglected to shut the air intakes. The fumes filled the prison’s interior spaces and the prison had to be evacuated overnight. As the manufacturer’s representative said, “You can’t just put up prisoners overnight in the local Motel 6.”
Additionally, aged roofs that have not been maintained since installation may be in such disrepair that a coating alone is insufficient to save the roof, says Ripps.
For facilities with known roof leaks, it’s advisable to check any roofing or plenum insulation for wetness. Eventually, wet insulation will cause headaches for facilities managers who do not adequately solve the problem.
“It is always a no-no to install products over roof systems where insulation is saturated with moisture,” Ripps says. “Eventually that moisture needs to escape by evaporation and will blister or delaminate any roofing product applied over it.”
Nelligan says that most facilities managers look to coatings to extend roof life. “We have clients who recoat their roof every 5 years – because they don’t want to tear the roof off,” he says. “It’s expensive and can cause business disruption.”
Nelligan also says that it’s important for facilities managers to remember that coating costs generally are expensed the year they are applied – they’re not capital costs spread over a multiple-year timeline, which can be the case for reroofing.
But coatings can help mitigate other roofing costs as well, including the environmental costs associated with disposal of the old roof.
“When you put together disposal costs and the costs of business disruption,” Nelligan says, “coatings make real sense.”
The Roof Coatings Manufacturers Association (RCMA) is the national trade association representing manufacturers of cold-applied protective roof coatings and cements, as well as suppliers of products, equipment and services to the industry.
Since its founding in 1982, RCMA has grown to be a respected voice in the building-construction industry. The association has tripled its membership to almost 60 manufacturing and supplier member firms and affiliate and contributory members. Association benefits and activities include:
Contact RCMA at 202-207-0919.