By John Becker
One of the most important assets any facility can have is the one that keeps it covered—the roof. As one of the largest building components, cool or emissive roof systems can impact energy efficiency and provide significant cost savings through solar reflectivity and thermal capacity.
These types of roofs are designed to stay cool in the sun by minimizing solar absorption and lessening the transfer of heat from the roof into a building. Highly reflective and emissive single-ply roofing membranes offer many benefits including reduced energy use, reduced air pollution, and reduced greenhouse gas emissions. In addition, green building programs advocate the use of cool roof systems to negate the urban heat island effect created from dark rooftops, asphalt parking structures, and sparse vegetation.
Once installed, it is imperative to maintain the roof’s reflectivity in order to fully recognize the overall energy and cost savings. The accumulation of airborne particles, dirt, debris, and biomass can cause up to a 40% loss in cool roof reflectivity. For areas with high cooling loads, this can significantly impact the energy savings associated.
The beauty of these types of roofs is their ability to be easily cleaned and maintained to ensure a longer roof life cycle. Most accumulation of dirt, debris, and vegetation can be simply removed using brooms and brushes. In places where there is standing or pooling water, it might be necessary to clean out the drain screens or snake the roof drain pipes or down spouts. Pressure washing at the lowest setting can also easily remove most built-up grime and mildew. Lastly, specialized detergents designed for single-ply roof systems may be used. However, it should be noted that petroleum based solvents, harsh abrasives, or citric based cleaners are not recommended as these may damage or deteriorate the roof membrane.
All of these things can be done by facility maintenance personnel. However, the more square footage a building has the more time and effort it is going to take. In addition, if the roof has not been cleaned in some time and debris has been allowed to build up significantly, it is often better to call in a professional contractor. Often times, they will be better equipped to handle more square footage, and have heavier equipment and access to detergents designed specifically for the roof system.
Overall, though, the best solution for maintaining the reflectivity of a cool roof is to establish a preventive maintenance plan that routinely inspects the roof at least twice a year, typically before and after the region’s most severe weather season. For instance, in the Northeast, inspections should be done prior to the winter freezes and storms and then after the last snowfalls. In the Southeast, summer would be the severe season, with its high heat indexes and cooling rains that can cause thermal shock. These inspections can vary in scope, complexity, and intensity so it is imperative to partner with a competent roofing consultant or contractor to ensure each roof is evaluated comprehensively. In addition, to retain most roofing system manufacturer’s warranties, it is required that any maintenance or repairs be performed by a certified maintenance professional (CMP) or a certified contractor approved by the manufacturer.
In addition to the normal inspection, moisture surveys should be done periodically on existing properties within the portfolio but especially when a property is being purchased or sold. Moisture surveys measure the properties of the roof materials that change when there is water present. Most commonly, these are done in the form of infrared (IR) scans that measure the amount of heat retained through wet insulation. While there are other types of methodology for detecting roof moisture, an IR scan is the only non-destructive and unobtrusive type. These in depth scans can detect and document places within the roof system that have been compromised to roof leaks. By conducting these types of detailed analyses, roof systems can be evaluated for establishing a proper maintenance program and remedied prior to loss of business and revenue.
Formal energy audits should also be conducted by a seasoned roofing industry professional periodically and should be integrated into any new roof construction or replacement project. Energy audits can give a detailed comparison analysis of different types of roof systems and components and project the cost savings realized through the life cycle of the roof. These types of evaluations examine numerous factors including environmental conditions, insulation, building codes, air barriers, and the building’s interior climate. By assessing all of these factors, the energy audit can help improve and optimize the energy savings realized from cool roof systems.
While cool roof technology has been around for a long time, the potential for long-term sustainability is just now being fully realized. By preserving a facility’s cool roof system, the timetable for tear off or replacement is decelerated equating to less waste in landfills and less energy consumed from new material manufacturing processes. Overall, cool roof systems that can withstand years of use without degradation due to routine inspection, maintenance, and cleaning can provide better energy efficiency and cost savings.
Becker is the Roof Guard Program Manager for North American Roofing, a national, commercial roofing contractor based in Asheville, NC. He directs and manages the Roof Guard Asset Management Program, a platform designed to prolong the life of existing roof systems.