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I work for a lightning protection company in Colorado. We are having more metal roofs installed all over the United States, from homes to prisons. With almost all of these buildings there is computers involved in the structure or the controls of the structure. Therefor we are seeing increased demand for lightning protection to help protect from lightning.
We have seen many problems with metal roofs and exterior mounted lightning protection systems. Lightning protection systems are typically attached by screws, or use adhesive, or a pressure bolt system on metal seamed roofs. This includes aprox. 6 fasteners for each base to hold the lightning rod and 1 fastener for each 3' of cable that runs to all of the lightning rods. All of these types of fastening methods have their draw-backs. The screws have the potential for leaks and can "tear" metal roofing when a snow load shifts. Snow loads can also break the bond of the adhesive or the pressure bolt. The obvious conclusion is that there can be damage to the metal roofing and the lightning protection system that would have to be repaired or replaced.
Another option is to mount the lightning rods and cable below the metal roofing with the rods coming through the roofing material. With lightning rods being spaced at 20' centers, this can be a lot of penetrations with the potential of leaks at each of these locations.
The last known option is for a lightning protection system known as an E.A.S.E. (Electronicly Activated Streamer Emission) system. This system typically has only one roof penteration and relys on the structural members of the building for its support and not the roofing system. Conductors are typically run below the roofing material which eliminates the potential problems of running the conductor on the roof.
I would like to know if the Metal Roof Association has an installation method which is preferred or which one of the above mentioned lightning protection systems would work best with metal roofing?
8/13/2002
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