ERA | EPDM Roofing Association

Protection from Summer Storms: The Science Behind the Durability of EPDM

Protection from Summer Storms: The Science Behind the Durability of EPDM

June 30, 2015 16:08

In light of the increasing frequency of severe hailstorms, the ability of a roof to withstand these storms has become a significant factor in roof system selection. According to research conducted by the National Oceanic and Atmospheric Administration’s (NOAA) National Severe Storms Laboratory, the “hail belt” area of the United States is getting larger. This means that regions which were not typically prone to hailstorms in the past are now regularly receiving hail fall greater than ¾ of an inch in diameter. For example, an article from Construction Canada Magazine found that damage from hailstorms in 2010 was so extensive, the dollar values accounted for approximately half of all insurance claims across the country.

A larger hail belt, combined with more frequent hailstorms, means that an increasing number of buildings need roofs that can withstand the abuse of these hailstorms. Most asphalt-based products and white plastic-based membranes become increasingly brittle with age, and therefore more susceptible to severe damage from hail impact. A number of recent studies comparing the performance of different roofing systems in moderate or severe hailstorms conclude that EPDM is the most hail-resistant roofing system on the market today.

EPDM Provides Superior Protection Against Hail
Roofing experts agree that EPDM performs especially well in hail conditions for the following reasons:
• EPDM's inherent elasticity and flexibility allow it to resist impact
• EPDM retains the bulk of its impact resistance as it ages
• Ballasted EPDM systems provide a protective layer atop the membrane
• Adhered EPDM systems eliminate protrusions caused by fasteners and plates

A 2009 study conducted by Jim D. Koontz, PE, RRC, and Thomas Hutchinson, AIA, CSI, FRCI, RRC, used the “hail gun” test to compare new, heat-aged, and field-aged EPDM membrane samples. The test used compressed air to propel ice spheres into vertically mounted 4’ x 4’ EPDM roof deck assemblies. The assemblies, or “targets,” were constructed by attaching the membrane to a variety of substrates, including polyisocyanurate insulation, wood fiberboard, and oriented strand board. To simulate hail conditions, the materials were sprayed with water at 40°F; then, hailstones measuring 1.5”, 2.0”, 2.5”, and 3.0” were fired at the models.

Field Tested, Research Approved
Of the 25 “new” EPDM assemblies tested in the Koontz study, 24 targets were not damaged. The field-aged samples performed admirably with only four failures out of the 36 assemblies tested; most of that damage was found directly over a mechanical fastener or plate. The research by Koontz and Hutchinson, as well as research from another roofing industry veteran, Ric Vitiello of Benchmark Services, all concludes that EPDM offers a high degree of hail resistance and retains the bulk of its impact resistance as it ages, making it an excellent choice for roof systems in this country’s ever-increasing hail belt.

The results from these studies and over 50 years of field service, combined with extensive warranty coverage and cost effective options, make EPDM roofing the leading choice in areas of the country with significant hail fall.

Roofing professionals like Mark J. Sobeck, RRO, have been specifying EPDM roofing systems for more than 30 years. This video chronicles an EPDM roof that has been performing for 31 years and is still going strong, despite its location in an area that receives severe hailstorms.

Robert Reale, Carlisle Creative Services

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