b'Steep SlopeMetal Nonmetallic Combustible Structure Roof Roof RoofMetal 0.5 1.0 0.5Nonmetallic 1.0 1.0 1.0Combustible 2.0 2.5 2.0A lightning protection system is recommended if buildings exposure to lightning exceeds tolerable risk as calculated based on the following:Exposure Criteria: FOUNDATION Lightning Flash Density:This is the average cloudto ground lightning flashes MRCA FOUNDATION per-square kilometer per SUPPORTS YOUR year as based on localmeteorological data or the ROOFING BUSINESSAverage U.S. LightningFlash Density Map from TheMRCAFoundation the National Lightning AD HERE raisesawarenessand Detection Network. Whiledensity varies, every state in improvestheRoofing the Country is at risk. IndustrybysupportingEquivalent Collection Area:This is essentially based on Without a lightning protection system, the lightningeducational programming, attached to the building along the metal parapet. It then the footprint of a building arced into the steel reinforcing in the wall, shattered theindustryresearch,and adjusted by the height ofthe building. The larger and grout-filled masonry units, and created hazardous fallingacademicscholarships. debris. The power continued to wreck havoc on its way to taller a building, the greater ground. Photo courtesy of Mr. Lightning. Your ongoing support of its exposure. the MRCA Foundation is Tolerance Criteria: critical to sustaining thisValue of building contents. Construction coefficient based on conductivity and combustibility of important mission. structure and roofing: Ease of evacuating building occupants. To make your 2020Continuity of service requirements and environmental consequences. commitment to the Regardless of the outcome of the risk assessment, Foundation, go toprotection should be given serious consideration if any of the following are factors: www.mrca.orgLarge crowds. Continuity of critical services. High lightning flash frequency. Tall isolated structure. Explosive or flammable materials. Irreplaceable cultural heritage. Statutory, regulatory and insurance requirements.www.mrca.orgMidwest Roofer 332.25x9.875.indd 3 8/23/17 3:34 PMBE_Winter18_MetalRoofingFeature.indd 31 1/19/18 11:35 AM'