Contractors and architects in search of sustainable and energy-efficient roofing products increasingly face a broad range of new choices. But a recent study suggests that a frontrunner in the race to be green may be one of the most tried and true products in the marketplace.

Contractors and architects in search of sustainable and energy-efficient roofing products increasingly face a broad range of new choices. But a recent study suggests that a frontrunner in the race to be green may be one of the most tried and true products in the marketplace. The new study shows that EPDM roofing, available for more than 30 years, is giving Planet Earth a helping hand by doing its job very well and for a very long time.

A common objective of sustainable building practices is to achieve a service life of 60 years. For roofing, this presents a special challenge. The typical roof system is often “out of sight and out of mind” as far as building owners are concerned, receiving service only when it leaks. At the same time, it serves as a work platform for an increasing amount of equipment and building utility systems: heating and air-conditioning units, plus a growing number of wind turbines and solar heating units. Given these demands, it will take a very tough roof to perform well for the 60 year benchmark.

The results of a recent long-term service life study of EPDM roof systems proves conclusively that EPDM delivers durability for decades. EPDM roof systems have been in the North American low-slope roofing market for almost 30 years, and many of these roof systems, including those installed more than two decades ago, are still providing useful service. Customers have long maintained that well designed and installed EPDM roof systems can attain service lives of 25 years and more. Marc N. Boulay, Chief Engineer of Northridge Consulting Engineers in Southeastern Massachusetts, says that the longevity of EPDM is demonstrated across the major domestic manufacturer brands. “My main client has tens of millions of square feet of EPDM roofs in service in North America, a fair percentage of which are well past 20 years old, numerous past 25 and a few closing in on 30.” In order to provide scientific evidence to back up these observations, the EPDM Roofing Association (ERA), commissioned a study of long-term performing EPDM roofs and how they were managed in an attempt to provide extended watertight protection.

The Research Study

The goals of the long-term service life study were to:

• Verify the long-term performance characteristics of EPDM membrane.

• Validate empirical sustainability experiences.

• Create a foundation for specifier-to-owner discussions in regard to long-term service life.

To conduct this study, samples from five roof systems, installed between 29 and 32 years ago, were collected for analysis. They were:

1. A ballasted, 45-mil EPDM roof membrane, in place for 32 years at the Jacobetti Center of Northern Michigan University in Marquette, Mich.

2. A ballasted, 45-mil EPDM, in place at the Jamrich Building for 29 years, also at Northern Michigan University

3. A ballasted, 45-mil EPDM in place for 28 years at the North Asheboro Middle School in Asheboro, N.C.

4. A ballasted, 45-mil EPDM in place for 29 years at a warehouse facility in West Bend, Wis.

5. A fully adhered EPDM, in place for 29 years at the Barrington Combined Community School District 220 Headquarters in Barrington, Ill.

The samples were sent to Momentum Technologies, a testing facility for the roofing industry, in Uniontown, Ohio, where the following tests were performed:

• Elongation (percentage)

• Tensile Strength (psi)

• Thickness XD (Cross Direction) (inches)

• Thickness MD (Machine Direction) (inches)

• Factory Seam Strength (psi)

The Factory Seam Strength tests were done using the ASTM Standard D816, Standard Test Methods for Rubber Cements. The other four tests were conducted, using the ASTM Standard D4637, Standard Specification for EPDM Sheet Used In Single-Ply Roof Membrane. In addition, manufacturer minimum physical characteristics for new EPDM were applied to the results.

Those results showed that all of the samples were essentially performing like new products: They had physical characteristic properties above or just below the minimum physical characteristics of 45-mil EPDM membrane being manufactured today or for aged EPDM.

For example, regarding Elongation Test Results (Figure 1), four of the five roof samples exceeded the minimum characteristics for aged EPDM, and one exceeded the minimum for new EPDM, with another roof nearly exceeding the minimum for a new product.

For Tensile Strength (Figure 2), all five samples exceeded the minimum standard. For Thickness XD (Cross Direction) (Figure 3), three samples exceeded the manufacturer mininum, while the other two missed by one-thousandth of an inch.

For Tensile Strength MD (Machine Direction) (also shown in Figure 3), three achieved or exceeded the minimum, while one missed by one one-thousandth of an inch and another by four one-thousandths of an inch. For Factory Seam Strength (Figure 4), it was only possible to test two of the samples and both easily surpassed manufacturers’ minimums.

These test results validated the results of earlier, anecdotal studies and determined that properly designed, installed and maintained EPDM membranes can successfully withstand the effects of very harsh climates. It also indicates that these roofs and other EPDM systems can approach or exceed 40 years of service life. Long service life means less frequent need to replace a roofing system, conserving the financial resources of the business owner and the energy resources of the environment.

Given the sustainability target of 60 years for roofing systems, these particular samples are now being heat-aged to simulate use at prorated “life spans” of 40, 50 and 60 years. It should also be noted that these tests were conducted solely on 45-mil membrane. In the time since their installation, the manufacturers of EPDM have introduced 60-mil and 90-mil EPDM, and both are likely to have service lives that exceed the performance of 45-mil EPDM, perhaps 50 years or more. It is important to note that these roof systems were properly designed, installed and maintained. Certainly those factors combined with the inherent durability of the membrane to allow for this type of service life. In addition, all of the samples were taken from moderate to cold climates, since that is where EPDM roofing has been used for at least three decades. But industry experts say that white EPDM, now widely used in warmer climates, can be expected to deliver the same long service life.