Deferred maintenance has been one of the great failings of many of the nation's education institutions, and roofs — out of sight, out of mind — are one of the easiest elements of maintenance to neglect.
Of course, as many administrators have learned through the years, the cost of putting off routine inspections and preventive maintenance can be leaks, mold growth, serious structural damage to a facility and serious health risks for students and staff. As more schools and universities have begun to embrace green strategies in building and maintaining their facilities, the health and safety of the indoor environment is driving facility managers to be more vigilant about roofing maintenance, and to seek out roofing types that can conserve energy and have less impact on the environment.
Although many schools and universities don't have enough maintenance staff and resources to inspect all their roofs twice a year, that is what roofing experts recommend.
Inspections in the fall will enable maintenance workers to clear a roof of leaves and other debris before winter weather strikes, and a spring follow-up will reveal whether the roof sustained any significant wear or damage during the winter.
“A proper inspection program is an important aspect of maintenance and can identify problems before they impact energy use and affect occupants' health,” says the Collaborative for High Performance Schools (CHPS) Best Practices Manual.
The CHPS urges schools to maintain thorough records about each roof — the type of roof, its size, its installation date, the contractor, warranty information, and a history of inspections and repairs.
Inspections should include checks on cap flashings, edge metal, base flashings, penetrations (pipes, drains, exhaust), field of the roof, ballast, and roof adhesives and coatings.
On the roof membrane, inspectors should check for worn spots, blisters, holes or deteriorating sections, the CHPS manual recommends. For flashings, workers should look for any loose or missing fasteners, corrosion, and cracking or aging sealants. If possible, workers also should inspect the interior of the roof to see if moisture has penetrated the building.
School maintenance staff should ensure that any runoff drains properly from a roof, and that roof edges are properly secured. Minimize foot traffic on a roof and provide protective walkways in areas where traffic is expected.
If an education institution decides to replace a roof, it must take special precautions if the existing roofing contains asbestos.
“When asbestos is disturbed by sanding, cutting and other renovation-type activities, asbestos fibers become airborne, creating an added risk of lung cancer and other lung diseases,” the CHPS manual warns.
About 90 percent of roofs in the United States are dark-colored, according to the U.S. Environmental Protection Agency (EPA). Those roofs typically absorb greater amounts of heat from the sun and force a building's cooling system to work harder to keep the interior comfortable.
The phenomenon is exacerbated in urban and suburban areas that experience the “heat-island effect.” The high density of buildings, pavement and vehicles in those areas can result in temperatures 2 to 10 degrees (Fahrenheit) higher than nearby rural areas.
One of the primary strategies for combating the heat-island effect and easing the demand placed on a building's cooling system is installing a cool roof.
Two critical characteristics of cool roofs are high solar reflectance — the percentage of solar energy that is reflected by a surface — and high thermal emissivity — the percentage of energy a material can radiate away after it is absorbed. The less heat a roof absorbs, the less energy that is needed to keep a building cool.
“By limiting the quantity of absorbed solar energy, damage from ultraviolet radiation and daily temperature fluctuations — which cause repeated contraction and expansion — can be reduced,” the EPA says.
With less wear and tear, cool roofs will last longer.
“Since solar radiation is a major cause of roof deterioration, cool roof coatings can significantly increase the life of the roof membrane,” says the CHPS Best Practices Manual.
Schools can make their roofs cool by applying coatings or by installing cool single-ply membranes. The EPA says cool roof coatings typically are white liquids — elastomeric, polyurethane or acrylic — with the consistency of thick paint. Applied over an existing roof structure, they can last 10 to 20 years, depending on quality and thickness.
The CHPS Best Practices Manual recommends that schools that have asphalt roofs with a cap sheet or a modified bitumen roof should apply coatings with an initial reflectance of 0.7 and emittance greater than 0.8 (both measures represent a scale from 0.0 to 1.0 — the higher the number, the “cooler” the roof).
The types of cool single-ply membrane roofs include ethylene-propylene-diene-terpolymer membrane (EPDM), an elastomeric material; polyvinyl chloride (PVC), a synthetic thermoplastic polymer; and thermoplastic polyolefin (TPO), a blend of polymers that also may contain desirable additives such as flame-retardants or UV absorbers. It can last 30 years and is largely maintenance-free. PVC is the most expensive of the three, but has a track record of long-term performance, the EPA says.
Green on top
The University of Pennsylvania has installed its first “extensive” green roof on its Philadelphia campus.
The environmentally friendly roof sits atop the English House/Kings Court student residence. The university says the roof has low-maintenance alpine sedums and mosses, which grow slowly but eventually provide a dense cover that does not need watering or maintenance.
Green Roofs for Healthy Cities, an association that works to promote green roofs, cites numerous benefits of green roofs. The layers of a green roof can prolong the life of a roof membrane; provide insulation to reduce energy costs and noise; provide more stormwater retention; and convert carbon dioxide to oxygen. On some green roofs, herbs, flowers and vegetables can be grown and reduce food-service costs.
The university says installing the roof will benefit the campus in several ways:
Evaporative cooling will counteract the heat-island effect and reduce the temperature on the top floor of the building.
The additional insulation will help moderate winter temperature swings on the top floor.
By retaining storm water, the roof will help the university manage campus discharge and prevent flooding.
The vegetation will protect the waterproofing membrane from ultraviolet radiation and from frost. This will reduce leaks and help extend the life of the roof.
The roof will support wildlife (including beneficial insects and some migratory birds), and provide beautiful scenery.
Percentage of roofs in the United States that are dark-colored.
150 to 190
In degrees Fahrenheit, the temperature reached by dark-colored, low-reflectant roof surfaces.
Source: U.S. Environmental Protection Agency