1 Aging and Hail Research of PVC Membranes Frank J. Foley, Jim ...
1 Aging and Hail Research of PVC Membranes Frank J. Foley, Jim ...
1 Aging and Hail Research of PVC Membranes Frank J. Foley, Jim ...
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<strong>Jim</strong> D. Koontz, P.E., is a consulting engineer with <strong>Jim</strong> D. Koontz & Associates, Inc. <strong>of</strong>Hobbs, New Mexico, a ro<strong>of</strong>-engineering firm. With 30+ years <strong>of</strong> experience in hailinvestigation, ro<strong>of</strong> research, ro<strong>of</strong> consulting <strong>and</strong> laboratory analysis <strong>of</strong> ro<strong>of</strong>ing materials,he has authored numerous technical articles <strong>and</strong> presented ro<strong>of</strong> seminars regarding avariety <strong>of</strong> ro<strong>of</strong> topics.Joseph K. Valaitis, M.S., is an independent research consultant with Valaitis Consulting<strong>of</strong> Brecksville, Ohio for the rubber <strong>and</strong> plastics industry. He brings 37 years <strong>of</strong> chemicalresearch experience that includes 24 technical articles, chapters to h<strong>and</strong>books onrubber technology <strong>and</strong> 19 patents in polymer mechanics <strong>and</strong> ro<strong>of</strong>ing chemistry.1.0 INTRODUCTIONSix distinct categories <strong>of</strong> membrane systems dominate the current United States lowslopero<strong>of</strong>ing market: built-up asphalt; built-up coal-tar pitch; thermoset rubber (EPDM);SBS-modified bitumen; APP-modified bitumen; <strong>and</strong> thermoplastics (<strong>PVC</strong>, <strong>PVC</strong> alloys,<strong>and</strong> TPO). Selection <strong>of</strong> the optimum ro<strong>of</strong>ing solution for a given project is dependentupon a number <strong>of</strong> building owner's criteria (Table 1). Although some owners focus ononly a few criteria, others may have multiple reasons for selecting a particularmembrane system. All <strong>of</strong> these categories <strong>of</strong> ro<strong>of</strong> systems demonstrate benefits toowners. No single classification <strong>of</strong> ro<strong>of</strong> system satisfies all criteria because each bringsdistinct features to a vast spectrum <strong>of</strong> owner <strong>and</strong> building needs.Initial installed cost Speed <strong>of</strong> installation Warranty <strong>and</strong> perceived health <strong>of</strong>supplierWeight Ease <strong>of</strong> leak detection UV <strong>and</strong> ozone resistanceImpact upon energy Ponding resistance Ease <strong>of</strong> applicationFire rating Aesthetic appearance Life cycle costWind rating Chemical resistance Impact <strong>and</strong> abuse resistanceEnvironmental impact(degradation/disposal)Tolerates movement (thermal<strong>and</strong> structural)Performance in extendedextreme temperaturesEase <strong>and</strong> integrity <strong>of</strong> repair Ease <strong>of</strong> accurate inspection Timeline length -- signal <strong>of</strong>degradation to replacementRo<strong>of</strong> pr<strong>of</strong>ile -- density <strong>of</strong>Compatibility with system Use <strong>and</strong> climate <strong>of</strong> buildingpenetrations, accessibility components <strong>and</strong> deck typeTable 1: Criteria in membrane system selectionHowever, when selecting any ro<strong>of</strong>ing system, specifiers <strong>and</strong> owners must consider thepotential causes <strong>of</strong> failure <strong>of</strong> their selected ro<strong>of</strong>ing system. <strong>Hail</strong> events in particular canundermine a careful membrane selection because <strong>of</strong> a sudden <strong>and</strong> complete loss <strong>of</strong>waterpro<strong>of</strong>ing, resulting in damage to equipment, product, interior finishes, businessenterprise, <strong>and</strong> building structure. The authors have observed hail damage to allexposed ro<strong>of</strong> systems - from thin, non-reinforced, elastomeric skins to thick, reinforced,multi-layer composites. “Exposed” here is defined as any ro<strong>of</strong> system not covered withstone.2
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