By Colin Murphy, RRC INTRODUCTION The following article is the first in a series of three addressing hail damage to shingles The article provides an overview of the history of shingle system testing and is a preface to the second and third articles, which address actual hail data and the future of shingle hail testing The Roof Consultants Institute has sponsored the second phase of testing. A technical paper will be delivered in Dallas at the 1998 RCI Convention and Symposium addressing the test protocol and results The two most common causes of weather damage to asphalt composition shingles are wind and hail. Research and development work first carried out in the 1950s addressed the former with the development and implementation of the sealing strip, a heat activated adhesive strip placed adjacent to the nail line that bonds the overlapping shingle to the base shingle layer close to the point of mechanical attachment. Shingle manu¬ facturers quickly adopted this advance in wind-resistant shin¬ gle design and, in turn, the number of wind-damaged shingle installations was reduced In the late 1960s, a wind resistance test was developed to document the performance of asphalt shingles with an adhe¬ sive strip. The test subjects a “conditioned” shingle assembly to forced air blown at 60 miles per hour (97 kph) from a 36” x 12″ opening for a period of two hours or until failure. The American Society of Testing and Materials (ASTM) adopted the test protocol in 1972 under the designation D 3161 1 Thereafter, Underwriters Laboratories adopted the test pro¬ tocol, under the designation UL 997^, as part of the require¬ ments for shingle system classification. Shingles are typically warranted to resist wind gusts of up to 60 miles per hour (97 kph). Development of more wind resistant shingles has been ongoing Very few shingles tested under the ASTM protocol have passed at wind speeds in excess of 60 miles per hour Testing to elevated wind speeds, as discussed below, has resulted in further UL classifications under the Prepared Roof Covering Materials (TFVC’Z) section in the 1997 UL Roofing Materials and Systems Guide. 1 After Hurricane Andrew, which struck South Florida in 1992, the South Florida Building Code established two new wind related requirements for asphalt shingle systems. Metro-Dade County Protocol PA 1004 subjects a large (10 ft. x 10 ft.) shingle assembly to wind forces in combination with simulated wind-driven rain. Forced air is blown at the test specimen at incrementally increased wind speeds during a simulated rainstorm. Metro-Dade County Roofing Protocol PA 1075 subjects a “conditioned” shingle assembly to a maximum wind speed of 110 miles per hour (180 kph) for a period of two hours or until failure. The protocol is based on ASTM D 3161 / UL 997, with an elevated wind speed requirement. As a result, the 1997 UL Roofing Materials and Systems Directory includes six shingle systems classified to wind speeds in excess of 60 miles per hour (97 kph). Wind speed classifica¬ tions range from 90 to 110 miles per hour (145 to 180 kph). The South Florida Building Code also requires that shingles marketed within the Metro-Dade jurisdiction comply with the physical property requirements of ASTM D 3462 6. As a result, some manufacturers have increased mat weights to meet these requirements. Initially, only shingles that successfully passed at elevated wind speeds were submitted for physical property testing. Within one year of the test requirement, most shingle manu¬ facturers reformulated/redesigned their shingles to meet the new requirements, however, the manufacturers’ wind war¬ ranties have remained at 60 miles per hour for the great majority of asphalt composition shingles. Research on both shingle products and associated test methods is ongoing today The most prominent is a multi¬ year project sponsored by the Asphalt Roofing Manufacturers Association (ARMA) at the University of Colorado/ The project is multi-phased, first addressing the effects of wind on shingle assemblies, and eventually, addressing a new test criteria for wind resistance of discontinuous roof assemblies Prior to 1992, the only shingle offering a 100 mile per hour (161 kph) wind warranty was Herbert Malarkey Roofing Company’s modified bitumen “Hurricane” shingle. While today there are six shingle systems that are UL classified to wind speeds in excess of 60 miles per hour (97 kpFO, only two of the six offer a wind warranty in excess thereof. Shingle damage resulting from wind speeds in excess of 60 miles per hour has been, and continues to be, considered an insurable event In contrast to the industry-wide research and development 12 • Interface January 1998 Average hail days in the United States. Source: Weatherwise dedicated to wind resistance, hail resistance in shingles has, until the early part of this decade, received far less attention While limited hail testing of steep slope products has been carried out over the last four decades, testing has followed no common procedure. Therefore, data from one program can¬ not be compared to that from another. Moreover, no test standard for hail or impact resistance has been developed or adopted by United States building code agencies or ASTM. Hail has been considered an act of nature and, therefore, an insurable event, regardless of storm intensity. Conse¬ quently, the cost to insurers for hail-related damage has been significant. This has resulted in the insurance industry taking a leading role in the development and implementation of a hail test standard. In recent months, the Texas State Insurance Commission has petitioned for the adoption of a new hail test and mandatory homeowner credits for the use of sloped roofing products that have been tested to be “hail resistant.” Hail is a weather event that occurs most frequently and at its highest severity within a small area of the United States: east of the Rockies and west of the Mississippi River The most severe hail areas cover approximately 8% of the United States A larger, moderate hail area includes approximately 80% of the United States, with 90% of the United States experiencing some sort of hail event annually (See map, above.) Hailstones form when moisture in a thunderstorm is held in the upper atmosphere between currents of rising air (updrafts) and currents of descending air (downdrafts). Hailstones vary in size, dependent on the magnitude of the updraft versus that of the downdraft Larger hailstones form if held in the atmosphere for a longer period of time. More¬ over, because hailstones are composed of frozen water and encapsulated air, the density and shape of hailstones will vary. Hailstorms are generally contained within a relatively small area, moving quickly within a confined path, making it diffi¬ cult to detect, follow and quantify the severity of a storm While new radar systems are capable of detecting and quan¬ tifying hail events, the technology is relatively new and human observation, with its inherent limitations, remains the primary source of data gathering. Hail data are gathered and reported to the Severe Storm Center of the National Weather Service Data are recorded after each observation in monthly tallies See Table i). Hail damage is not limited to roof damage. Damage to automobiles, livestock and crops contributes to the billions of insurance dollars paid each year to compensate for hail dam¬ age Hail has also been a cause of loss of human life in rare instances The extent and magnitude of damage caused by a hailstorm are dependent, in part, on the size and density of hailstones dropped by the storm. Larger and/or more dense hailstones incur greater impact energy on the object(s) being struck (See Table 2). Moreover, the population density, storm intensity and storm duration have a significant impact on the extent and magnitude of damage incurred While hailstorms have been primarily viewed as an unusual, insurable weather event, a major hail event in an urban area can result in hundreds of millions of dollars in roof damage January 1998 Interface • 13 Storm Data and Unusual Weather Phenomena Ealh No, Of Persons Est, Damage Character of Location Date Time Length Width Killed Injured Property Crops m TEXAS, Northern Strong winds blew down several trees onto power lines at Center and 1 mile west ofCenter. Tarrant County Watauga 22 1820CST 0 0?? Hail (0.88) N Richland Hills 22 1826CST 0 0 ? ? Hail (1.25) Keller 22 1832CST 0 0 ? ? Hail (1.00) Keller 22 1848CST 0 0 ? ? Hail (1.50) Dallas County 1 NW Coppell 22 1831CST 0 0?? Hail (1.75) Coppell 22 1837CST 0 0 ? ? Hail (1.00) Grayson County Luella 22 1849CST 0 0 ? ? Hail (0.75) Sherman 22 1857CST 0 0 ? ? Hail (3 00) Sherman 22 1910CST 0 0 ? ? Thunderstorm Winds Northern Portion 22 2230CST 0 0?? Flash Flood Southmayd 22 2O3OCST 0 0 ? ? Hail (1 75) Table 1 alone Such a hailstorm is a boom to the roofing industry, whereby contractors and wholesale suppliers travel to a stricken area to participate in the insurance-financed reroof¬ ing bonanza. Product shortages due to the resultant surge in demand increase prices within a wide region. Inexperienced installers and insurance defrauders add to the overall costs and the difficulty in providing quality roof replacements In short, hail events provide localized demand for new steep sloped roofs, increasing the sale of products and instal¬ lation labor The cost of the reroofing is primarily borne by the insurance industry There is little incentive within the roofing industry to reduce the demand for its products and services In contrast, there is a great incentive on the part of the insurance industry to reduce damage during a hail event Comprehensive hail studies began in the 1960s when Sidney H Creenfeld published findings of a hail test pro¬ gram intended to replicate damage incurred on a shingle assembly when installed over various substrates The test pro¬ gram, which was sponsored by the United States Department of Commerce, simulated hail impact through the use of a hail gun” that shot ice pellets at test specimens at a predeter¬ mined velocity After impact, the shingle was visually exam¬ ined and categorized as severe or superficial damage, as noted below ▼ Superficial Damage with no loss of weather¬ proofing capabilities ▼ Severe: Penetration of the shingle The Creenfeld test program examined a variety of sub¬ strates including shingles installed over 3/8 inch and 1/2 inch thick plvwood and I inch x 6 inch tonguc-and-groove decking with and without an underlayment Data from the Creenfeld test program indicated that a shingle s hail resistance decreased when the assembly includ¬ ed an underlayment. In theory, impact energy incurred on shingles with an underlayment was transferred to tensile loading within the shingle, which the organic mat shingles of the time were not able to absorb. To that end, comparative testing of organic shingles versus “new” fiberglass mat shin¬ gles provided data indicating those with a fiberglass mat had greater hail resistance. Lastly, testing of shingles and built-up roofing assemblies performed better on a more rigid substrate than on lighter, less rigid substrates. In 1978, ASTM published Test Method D 37469 in which steel missiles are fired at test specimens to simulate the impact energy incurred by a falling hail stone. The method has been used to test a variety of roof covers for impact resistance. During the 1970s, the majority of shingles produced were of a fiberglass mat. In 1983, ASTM published Test Specification D 3462. The ASTM specification established minimum physical properties for fiberglass mat shingles,- how¬ ever, the document makes no reference to minimum hail resis¬ tance criteria Moreover, system designers and industry mem¬ bers have made little to no change to the underlayments and decking materials over which shingles are installed, a variable clearly established as critical in the Creenfeld report In contrast to what appeared to be a blind eye view of hail resistance for steep slope roofing products, hail test standards and minimum requirements were developed and instituted for low slope roof systems In 1986, Factory Mutual Research Corporation (FMRC) amended its Test Standard 4470’0 to include a hail resistance test requirement for FM Approved Class I roof covers The test standard was revised in 1992 to include moderate and severe hail designations (Class l-MH and Class 1-SH, respectively). The hail test prescribes the use of a steel ball dropped onto various locations of the test spec¬ imen from a predetermined height. For a moderate hail 14 • Interface January 1998 Table 2 Characteristics of Free-falling Hailstones Size (in.) Weight (lbs.) Freefall Velocity (mph) Freefall Energy (ft. -lbs.) 1/2 0.002 34.7 0.09 3/4 0.007 42.3 0.44 1 0.017 49.8 1.43 1-1/4 0.034 55.9 3.53 1-1/2 0.058 61.4 7.35 1-3/4 0.093 66.2 13.56 2 0.138 71.6 23.71 2-1/4 0.197 75.7 37.73 2-1/2 0.270 79.8 57.48 2-3/4 0.360 84.6 85.95 3 0.467 88.6 122.66 3-1/4 0.594 93.4 173.21 3-1/2 0.742 97.5 235.67 3-3/4 0.913 101.6 314.71 4 1.108 105.7 413.31 .Approval (Class 1-MH), the steel ball is 1-3/4 inches in diam¬ eter dropped from 5 feet above the specimen. For a severe hail Approval (Class 1 -SH) the steel ball is 2 inches in diame¬ ter dropped from 17 feet 9-1/2 inches. Testing is performed on both “as received-” and UV-conditioned samples In contrast to the irregular ice pellets shot from a “hail gun,” the FMRC 4470 hail test incurs a specific, repeatable impact energy onto the test specimen surface. The repeatability inherent in the test method allows for data from one system to be compared to that from another. In 1996, Underwriters Laboratories published UL 22 1811 Similar in concept to the FMRC 4470 hail test, this UL impact test subjects a conditioned test specimen to the impact energy incurred by dropping steel balls of various diameters from various heights at predetermined increments When a series of impacts is complete, the specimen is examined for failure, through a magnified visual examination, or through subjecting the specimen to a flexibility test, or a combination thereof. While LIL 2218 is a repeatable test method, it is des¬ ignated as an impact resistance test, not to be mistaken for a hail resistance test. In Switzerland (a country affected by severe hailstorms), a test procedure using a 40 mm diameter plastic sphere to simu¬ late hail impact was developed The test method is slightly more complex than the aforementioned methods in that data gathered are not limited to “pass’ or “fail’ at a predetermined impact energy The data generated include the impact veloci¬ ty, backing and boundary conditions, and kinetic energy at which the specimen incurs damage The method also catego¬ rizes “failures based on type, form, extent and behavior While the shingle manufacturers have stated their commit¬ ment to studying the effects of hail on steep slope roofing products, research data have been kept, for the most part, proprietary The test data established have been generated without the benefit of an industry-recognized, repeatable test method to provide a baseline of data from which further research and testing could draw An attempt to resolve this problem and establish “baseline data” can be seen in work performed by Haag Engineering In 1993, Haag Engineering established a test protocol intend¬ ed for “controlled impact testing ” The protocol established not only a repeatable test procedure, but also a repeatable method of specimen examination and data analysis. Areas on the shingle test specimen are designated based on underlying support (unsupported, marginally supported, and fully sup¬ ported) and area location (field, edge, corner, upper trough, lower trough, etc ). After impact, shingle samples were desat¬ urated and examined for damage at these designated areas Damage is defined as “diminishment of the water shedding capacity or the reduction of expected long term service life of the tested materials.” In 1994, Exterior Research & Design, LLC began a test pro¬ gram based on examination and testing ol shingle systems that had experienced a major hail event Through review ol warranty cards from one shingle manufacturer, roofs were identified as being: ▼ Within the path of severe hail or ▼ Within the storm area, but outside of major hail impact areas Thirty-five applications of two shingle weights and ten applications of a third shingle weight were identified Shingle systems that endured the hailstorm with no subsequent repair were examined and samples were extracted from both sides of the roof ridge, approximately eight to ten courses up from the eave. In addition, neighboring homeowners were inter¬ viewed to determine whether their respective shingle systems had withstood the hailstorm with no repair work If the appropriate answers were given and the shingles could be positively identified, samples were taken from the same roof areas Sampling also included shingles taken from roofs installed in Seattle, WA during the same roofing season The Seattle shingles had not experienced a major hail event, but had been in place for an equal period of time The subject shingle applications were visually examined for damage Damage location (if any), underlayment and sub¬ strate data were recorded. Shingle samples were packaged and returned to the laboratory for further testing. Shingles taken from roofs outside the path of the storm were viewed and sampled in a similar manner Sampled shingles and new shingles of an identical type were conditioned in the laboratory, installed on test panels and tested for simulated hail resistance following the FMRC 4470 severe hail test standard Variables examined included roof pitch, underlayment type, deck type and impact loca¬ tion After impact, shingle impact areas were examined for damage under 30x magnification and desaturated for a view of the fiberglass mat condition Test procedure development and observations of weath¬ ered samples subjected to a major had event will be covered in Part II of this article. Comprehensive test data and conclu¬ sions will be covered in Part III January 1998 Interface *15 ITIW =h’l^ 1. ASTM D 3161, “Standard Test Method for Wind- Resistance of Asphalt Shingles (Fan-Induced Method),” ASTM Standards in Building Codes. Vol. 3, 1996. 2. (JL 997, “Wind Resistance of Prepared Roof Covering Materials,” Underwriters Laboratories, 1981. 3 Roofing Materials and Systems Directory, Underwriters Laboratories Inc., 1997. 4 PA 100-95, ‘Test Procedure for Wind and Wind Driven Rain Resistance of Discontinuous Roof Systems,” Dade County Building Code Compliance Office, 1995. 5. PA 107-95, ‘Test Procedure for Wind Resistance Testing of Non-rigid, Discontinuous Roof Systems,” Dade County Building Code Compliance Office, 1995. 6. ASTM D3462-93a, “Standard Specification for Asphalt Shingles Made from Glass Felt and Surfaced with Mineral Granules,” ASTM Standards in Building Codes. Vol. 4, 1996. 7. Everly, C., McCleur, R., et al, “ARMA Wind Research Program Report” Asphalt Roofing Manufacturers Association, July 1996. 8. Greenfield, S., “Hail Resistance of Roofing Products,” 1969. 9. ASTM D3746-85, “Standard Test Method for Impact Resistance of Bituminous Roofing Systems,” ASTM Standards in Building Codes. Vol. 4, 1996. 10. FMRC 4470, “Class I Roof Covers,” Factory Mutual Research Approval Standard, 1986. 11. UL 2218, “Impact Resistance of Prepared Roof Covering Materials,” Underwriters Laboratories Inc., 1996. About The Author Colin Murphy, RRO, RRC founded Trinity Group Fastening Systems, a company that developed fastening sys¬ tems for use in roofing assemblies, in <9 st. In tone, he established Trinity Engineer¬ ing, focusing primarily on forensic analy¬ sis of roof systems, materials analysis, laboratory testing and long¬ term analysis of in-place roof systems. The firm is based in Seattle, WA. Colin joined RCI in 1986 and became an RRC in 1993. He is currently the Director of Region VII. In 1996, he liras honored with the Richard Horowitz Award for excellence in technical writing for Interface. ASCE’s EdAC Clarifies Resolution Condemning ASTM Consensus Documents A recent press release from the Professional Firms Practicing in the Geosciences (ASFE) announcing that the American Society of Civil Engineers’ Educational Activities Committee (ASCE EdAC) had endorsed a resolution opposing the American Society for Testing Materials’ (ASTM’s) “promulgation of consensus documents that are labeled as Standard Practices or Standard Guides” has been characterized as “factually incorrect” by ASCE. According to a release signed by James E. Davis, ASCE Executive Director, the Midwest Civil Engineering Department I leads had prepared the said resolution, which was later endorsed by the Society’s Department Heads Council. The council then forwarded the resolution to ASCE’s board-level Educational Activities Committee for consideration, but no action has been taken to date on the issue. “ASCE has a long history of working cooperatively with ASTM,” Davis wrote. “Following further review of this issue, ASCE will work collaboratively to resolve any concerns the Society may have with ASTM.” Both ASFE and the Geo Institute have argued that the materials involved should be called something other than “standards,” claiming that the guides presuppose a standard client with standard risk management objectives for a standard project at a stan¬ dard site—conditions impossible to match in the “real world.” Hire the designers who created the RCI web site ’A’ The Written Word, Inc. w 0 * B_ 206.938.0990 * www.writtenword.com • wrttnwrd@nwlink.com 16 • Interface January 1998
