When it comes to installing lightning protection on your roof, there are a few special considerations to keep in mind. Thomas Smith, AIA, RRC, F, SEi, founder of TLSmith Consulting Inc., explains that in areas with strong winds, extra attention should be paid to the placement of the lightning protection system (LPS) so that it does not fade. UL 96A and NFPA 780 do not have specific requirements for areas with high winds. When it comes to metal roofs, the LPS conductors should not rest directly on the roof covering.
This is because the movement of the conductor, whether due to wind or heat, can wear down the surface of the metal panels. To prevent this from happening, the driver should be kept away from the panels as recommended by the Federal Emergency Management Agency (FEMA). If any product is subject to mechanical damage or unusual displacement, it can be protected with a molding or cover, but care must be taken so that the shock endings and other components mounted on the ceiling perform their function of accepting the accessories. The anchor sections of metal roofing and cladding systems are not built to carry current because, in most situations, the thickness of the metal used is insufficient to ensure a safe path for lightning.
Downward cables or downward conductors are the elements of the main conductive system that generally carry rays from the system at roof level to the grounding system. However, these occupied areas of the roof are usually located on the top or perimeter of a building and, therefore, direct lightning is likely to fall. Attention should be paid to locating and detailing lightning protection cables, connections and penetrations through the roof so that they do not interfere with the enjoyment of the terrace. Metal roofing materials are not combustible, so if lightning strikes a metal roof, a fire is less likely to occur than other types of roofing materials. Building enclosure case studies have shown that lightning protection systems can be successfully installed in five high-rise buildings with roofs or roof terraces.
In addition to wind liability, galvanic corrosion is a serious problem when installing copper components on metal roofs made of painted metal or galvanized aluminum. An effective LPS not only protects ceilings, walls and other structural components from direct lightning strikes but also protects electrical circuits, communications, process control systems and other elements that are vulnerable to indirect impacts. Installing a highly specialized LPS for a metal roof involves a combination of science, art, craftsmanship and technological acumen. To perfectly integrate lightning protection with occupied roof designs, metal elements can be placed on the roof where the overhead lightning terminals would normally be located. Contact East Coast Lightning Equipment for more information on specifying lightning protection systems for occupied roofs. If necessary measures are not taken for roof inclination, projections and metal roofing equipment, it can result in poorly protected roof areas or additional construction costs due to the use of excess components.
A network of grounding electrodes will largely depend on the experience and judgment of the person planning the installation while taking into account minimum requirements set by standards. The Associated Lightning Rod Company installed a unique lightning protection system in this special exhibition on the rooftop of the Museum of Modern Art in New York City.
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