In an area with hurricanes or high winds? Have a standing-seam metal roof that cannot meet the new wind load requirements? What about a metal building that makes lots of noise when it’s windy? One product solution may be an external purlin system. An external purlin for standing seam metal roofs, called WINDBAR, can add uplift strength to new and existing roofs. The principle behind the system is a patented Windstopper foot. A nonpenetrating clamp is placed evenly between roof clips on the standing seams, a square bar spans between clamps, and a bent metal strap attached to the bar over the middle of the panel prevents the panel from lifting. This “foot” then holds down the middle of the panel, resisting uplift under negative wind pressure. ASTM E1592, Standard Test Method for Structural Performance of Sheet Metal Roof and Siding Systems by Uniform Static Air Pressure Difference, is the standard that governs wind uplift. It simulates negative wind pressure on a roof panel system. During the test, the middle of the standingseam roof panel arches upward to such a great extent that it disengages the seams, causing roof failure. The company tested a standard 18-in.- wide, 24-gauge snap-together roof panel using the ASTM E1592 guidelines with its system and observed considerable improvements in performance with minimal seam deformation. For example, when roof clips were placed at 4 ft. on center with the external purlin system at 4 ft. spaced between the clips, the panel performance was doubled. Without the system, the panel failed (due to seam disengagement) at 41.6 psf. With the system, the panel failed (due to clip deformation) at 78 psf. Even more impressive, when the same roof panel system was tested at 1 ft., 6 in. on center, the limits of the testing chamber were reached before panel failure occurred. Without the external purlin system, the panels failed at 80.6 psf. With it attached, 250 psf—the maximum capacity of the test chamber—was reached. Thomas M. Shingler, PE, registered structural engineer and president of Design Dynamics, Inc. of Dallas, TX, observed the External purlins prevent panel uplift (photo courtesy of Marc Boulay). External purlin system on a standing-seam building in South Florida (photo courtesy of Marc Boulay). A u g u s t 2 0 1 2 I n t e rf a c e • 2 3 tests, collected and deciphered data, and prepared the structural report. The external purlin system improves the uplift performance of all standing seam metal roofs. Most jurisdictions in North America are now using the International Building Code (IBC), which replaces the Uniform Building Code (UBC). Many existing standing-seam systems do not meet all of the current requirements for wind uplift. In several cases, only the edge zone of the roof needs additional protection. In this instance, one would use the external purlin system only in select areas. The system has been factory tested to ASTM E1592 on several types of panels. It has also been field-tested. In Savannah, GA, external purlins were installed on a paper mill to resist wind uplift. Two years later, a hurricane blew through the area; and the mill was one of only a few buildings with standing-seam metal roofs that did not lose any of its panels. Another use for this system is for control of a “noisy” metal roof. Over the last five years, the system has solved noise issues on several projects throughout the United States, including numerous residences from Iowa to Wyoming. Recently, 3,000 linear feet of external purlin system were successfully 2 4 • I n t e rf a c e A u g u s t 2 0 1 2 www.rci-online.org/document-competition.html RCI 2013 DOCUMENT COMPETITION NEw – GREaTER RCI DOllaRs INCENTIvEs The winners of the 2013 RCI Document Competition will not only receive a plaque and recognition during the annual awards luncheon at the 28th RCI International Convention and Trade Show, as well as publicity of their winning projects in Interface, but also enjoy an increase in the RCI dollars awarded to them. RCI Dollars are awarded to nine winners in three categories: laRGE PROJECT | sMall PROJECT | REPORT 1st Place winners ………. 1,000 RCI Dollars 2nd Place winners ……… 500 RCI Dollars 3rd Place winners ……… 200 RCI Dollars RCI Dollars will be redeemable for any product or service provided by RCI or the RCI Foundation. RCI Dollars are redeemable by the award winner or by anyone specifically designated by the award winner. Use winnings for yourself or to help a friend or colleague buy a reference book or attend a seminar. The entry deadline is October 31, 2012. sEE wHaT IT TaKEs TO ENTER RCI, Inc. 800-828-1902 The external purlin system on the Lincoln County Justice Center in Hugo, CO, reduced roof noise due to wind uplift, strengthened the building, and gave snow-retention protection. External purlin system on a UPS building in South Florida (photo courtesy of Marc Boulay). installed on the Rehoboth Christian School in Gallup, NM, to provide sound attenuation. Another customer used the system on a metal building where the roof made so much noise that when it was windy outside, people could not use the space inside. After installing it as a test on one section of the building, the owner reported an almost complete noise reduction due to its addition. No laboratory testing has been done for noise reduction, but it has been field proven that the system reduces metal roof noise in some cases. On the Lincoln County Justice Center in Hugo, CO, the system served three purposes. First, it reduced roof noise due to wind uplift, which was the initial concern of the property managers. Second, it helped strengthen a metal building that had originally been underdesigned. Finally, it gave the building much-needed snow retention—an important feature in Colorado. The system is a good investment against roof failures, especially at the eave and edge zones of standingseam metal roofs, particularly in high-wind areas. Since WINDBAR is based on the proven SNOBAR snow retention system, in a large part of the country, an owner/architect can solve two problems with one solution. In this case, a designer must make sure to design not only for wind uplift, but also for snow protection, using the proper layout for both. A u g u s t 2 0 1 2 I n t e rf a c e • 2 7 Jason Nagaki, vice president of SNOBAR/WINDBAR, has been a driving force in the industry for over 17 years in various aspects of the research and development, design, and marketing for the company. Jason Nagaki Drawing for Windstopper patent describing use of WINDBAR system. the sheet. In the extreme, a thicker sheet could have no more weathering-side coating than a thinner sheet. Thus, the subcommittee proposed that the specified thickness of coating above the fabric or scrim be revised such that the coating thickness shall be a minimum of 0.015 in. (0.38 mm), or 30% of the total thickness of the sheet, whichever is greater. If a ballot for revision is successful, a 0.080-in. (2.0-mm) sheet would, for example, be required to have a coating thickness of 0.024 in. (0.61 mm)—about 60% thicker than presently required in D6878. D08 will reballot this proposed revision within the months ahead so that the results will be available before its December 2012 meeting. Status of Stan dar d D225 This document, Standard Specification for Asphalt Shingles (Organic Felt) Surfaced With Mineral Granules, is the responsibility of ASTM Subcommittee D08.02 on Steep Roofing Products and Assemblies. This standard is among the oldest of those under D08’s jurisdiction, having been originally approved in 1925. But times change and technology marches forward. According to the D225 task group, there are no longer any manufacturers of organic-felt shingles in North America. Furthermore, there are no known manufacturers worldwide, but this is not a certainty. Given this situation, the D225 task group recommended to the subcommittee that the standard be allowed to expire without revision and reapproval. It currently bears a 2007 date. Thus, according to ASTM rules and regulations, barring reapproval by 2015, it would be automatically withdrawn that year. The subcommittee neither accepted nor rejected the recommendation. Rather, it proposed an option of balloting the standard for withdrawal before the 2015 date is reached. No decision was made at the meeting. The topic will be revisited at a future meeting. In either case, the standard is seemingly destined for extinction—a stage in its career that organic-felt shingles appear to have already reached. Editor’s note: A separate article in the August issue of RCItems details awards presented to members of the D08 Committee at the spring meeting. Stucco and Exterior Finish Cladding Systems The Stucco and Exterior Finish Cladding Systems course is the second exterior wall-specific course that builds on the fundamentals presented in the Exterior Walls and Science program. The purpose of the course is to provide essential information on material properties, design principles, evaluation techniques, and repair methods for stucco and EIFS. Topics covered in this course include sound transmission, thermal bridging, coatings, testing methods, and the various codes and standards impacting stucco and EIFS systems. An RCI, Inc. Educational Program September 13-14, 2012 | Orlando, Florida Also offered at the same location: Exterior Walls Technology and Science September 11-12, 2012 | Orlando, Florida 16 CEHs | RCI Member Rate: $500 To register, visit: www.rci-online.org/education.html RCI, Inc. 800-828-1902 3 0 • I n t e rf a c e A u g u s t 2 0 1 2 The National Roofing Contractors Association (NRCA) has published a statement contesting the recent statement by the International Agency for Research on Cancer (IARC) classifying asphalt fumes as “probably carcinogenic to humans.” According to the IARC, the danger comes from “occupational exposures to oxidized bitumens and their emissions during roofing.” “Based on more than 20 years of research dedicated to the safe use of asphalt in roofing, NRCA believes IARC’s finding is at odds with the available scientific evidence,” the organization reported in Professional Roofing. NRCA Takes Position on Asphalt Fume Classification
