EPDM Roofing Systems Deliver Environmental Benefits
With more than a billion square feet installed across the globe, EPDM single-ply membrane has an impressive history of performance in the commercial roofing industry. EPDM has been utilized as a roofing material since the early 1960s, quickly gaining popularity among building owners and construction professionals because of its durability, cost-effectiveness, and quick and simple installation process. More than 50 years after its inception, with today’s building projects placing heavy emphasis on sustainability, EPDM is earning new respect in the green building community due to its long service life, low environmental impact, and ability to improve a building’s overall energy efficiency.
One of the best ways to conserve natural resources in any construction project is to use building materials with long life expectancies, thus reducing or delaying the need for their replacement. As one of the few roofing membranes with more than 50 years of history in the field, EPDM is unmatched in terms of long-term service life. Thirty-year-old EPDM has been known to exhibit physical properties that exceed those of new membranes, including tensile strength, water absorption rate, and tear strength.
In October 1981, G&E Roofing Company, Inc. was awarded a re-roofing project at the Cives Steel Paint Shop in Augusta, Maine. At the time, built-up roofs were one of the most popular commercial roofing systems, and EPDM was just coming to the forefront of the industry. Though EPDM was a newer product, testing had already shown that it would be an extremely durable membrane, and G&E decided to re-roof the 9,600-square-foot building with EPDM membrane. Having successfully installed EPDM roof systems before, they knew EPDM would be flexible and easy to install, enabling them to finish the project quickly while providing Cives with a highquality roofing system.
The G&E team began by completely tearing off the existing smooth-surface built-up roofing system. Once the existing system was removed, G&E loose-laid five inches of expanded polystyrene (EPS) insulation directly to the metal deck, and then installed the EPDM membrane in 20’ x 100’ and 45’ x 50’ sheets. Field-fabricated accessories were used to complete the roof details, and the ballasted system was finished with inch and a half stone loose-laid on top of the membrane. The project was completed in only three days, which G&E attributed to the EPDM membrane’s simple installation process and convenient roll sizes.
This roof has stood the test of time, requiring only minor repairs, the most recent of which occurred in May 2014, when edge metal and drain details were upgraded with pressure-sensitive flashings. EPDM remains repairable throughout its long life, another important attribute that speaks to the sustainability of this roofing system.
EPDM is available in both white and black colors for use in different climates. It is commonly accepted that white EPDM saves energy by reducing air conditioning usage, which is a major benefit in hot, southern climates. Somewhat less well known is the fact that black EPDM provides energy savings in cold, central and northern climates by reducing heating costs.
A recent study conducted by Ashley-McGraw Architects, PC and CDH Energy Corp analyzed various roofing systems in real-world conditions and concluded that in northern climates, dark-colored roofs are more energy-efficient and cost-effective than white roofs when heating and cooling expenses are examined. The study found that in northern climates during the heating season, the thermal heat loss associated with a white membrane is 30 percent higher than that of black EPDM, which translates to a 30 percent increase in heating bills for the building with the white roof. In addition, the study found that the cooling cost savings delivered by white roofing during the summer months does not outweigh this figure, particularly in buildings like schools that are closed in the summer months.
Another study, entitled “Life Cycle Inventory and Assessment of Low-Slope Roofing Systems in North America,” examined roofing systems that used a variety of membranes, including EPDM, TPO, PVC, and SBS modified bitumen. The study’s intent was to measure and compare the relative environmental impacts of different low-slope roofing systems through a Life Cycle Assessment (LCA), which is a scientific evaluation of the ecological aspects and potential effects of a product, process, or service throughout its lifecycle. This study’s LCA found that EPDM’s long-term environmental impact is much less than that of alternative roofing systems.
The study used the US Environmental Protection Agency’s Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts (TRACI) model to account for all inputs associated with the manufacture and installation of the different roofing systems. The results suggested that one of the most meaningful measures for comparing the relative environmental impact of low-slope roofing systems is the global warming potential (GWP) related to their manufacture, installation, and end-of-service-life disposition. The study held the service life constant at 15 years for all system types. The data showed that when compared to TPO, PVC, and SBS modified bitumen systems, EPDM roof systems have the lowest global warming potential, smog impact, and acid rain impact.
Stormwater management is a growing concern, particularly in large cities where stormwater and sewer systems are combined and sometimes unable to handle heavy rainfalls. In these settings, traditional ballasted EPDM systems can be modified to absorb and retain stormwater.
In many cities, a substantial rainstorm can overwhelm combined stormwater/sewer systems, causing raw sewage to be discharged into area waterways. In these settings, drainage board and moisture retention mats are often added to traditional ballasted assemblies, allowing the roof to retain as much as 67 percent of the water from a 24-hour rain event and providing substantial relief to public sewer systems.
Based on these findings, dark-colored EPDM roofing system is an energy-efficient and cost-effective solution, particularly for buildings in cool climates. There is no one roofing system that will deliver high performance and energy savings in every situation and location; a building’s geography, use, and contents must all be taken into consideration when choosing a roofing assembly. But when all the environmentally friendly attributes are evaluated, EPDM certainly rises to the top of the list of sustainable building materials.
Richard Stever is Environmental & Energy Efficient Solutions Product Manager at Carlisle Construction Materials.