Michael Faraday, a British physicist, discovered that a metal cage would shield objects within the cage when a high potential discharge hit the cage. The metal, being a good conductor, would direct the current around the objects and discharge it safely to the ground. This process of shielding is widely used today.

A Faraday Cage Lightning Protection System consists of Strike Termination Devices (air terminals) along the ridges, flat-roof portions and perimeters, interconnected with specialized lightning protection conductor coursed throughout the building, terminating at grounding locations.

The air terminals are spaced out at 20'-25' intervals around the perimeter and peaked ridges of structures and 50' intervals across mid-roof areas.  The specialized conductors consist of many small gauge wires interwoven in a rope braid to maximize the surface area.

Each 100' of perimeter requires a downlead.  A downlead is a cable connecting the roof-top lightning protection to a grounding location.  The grounding location is typically a ground rod or a series of ground rods, but it can also be a ground plate.  The grounding system can also include a counterpoise, which is basically a buried ground wire that interconnects all grounding locations and helps to make all grounding systems common.

This is the most well known and common lightning protection system and is certifiable by Underwriters Laboratories (UL).  UL provides a Letter of Certification to the owner for each building that passes a field inspection.  UL's inspection will verify that the work meets all current UL9A standards. 

Our UL number is E182594. 

Resources:  Underwriters Laboratories

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