Today, more so than ever, the typical residential home is susceptible to the risks of both direct and indirect lightning strikes.

Lightning not only poses the direct risk of fire to the home, but with more electronic equipment such as home entertainment systems, home office equipment, security alarm monitoring and modern appliances the risk of damage and loss is increasing.

Is your home at risk of being hit by lightning?

Following the simplified risk assessment guide below you can determine the level of risk your home is exposed to from lightning. It’s important to note that this risk assessment guide should be used as a guide on whether the risk is high enough to require direct strike protection to the home structure. The guide is a base on lightning frequency data from the southeast of the United States. Electrical power surge protection for the home in this modern world should be assumed as essential in reducing the risk of damage to electrical equipment within the home.

Even in cases with low risk of a direct strike to a home, the event is still possible, and the risk should be evaluated against the relative cost of undertaking protection for the home. In some states, a premium reduction on home insurance may also be applicable. Please contact your insurance provider for more information.

Direct Lightning Strike Protection for the Home

How to provide protection

A direct strike lightning protection installation for the home consists of the following four essential components (standard practice is defined within the LPI-175 installation handbook):

1 Air Terminals

The function of an air terminal is to capture the lightning strike, therefore each air terminal needs to be located on a point on the structure that has a higher probability of being struck by lightning. Some of these key design rules are stated below:

• Air terminals shall be provided on all roof projections (such as dormers, chimneys)
• Air terminals shall extend at least 10” above the roof-line or area to be protected.
• Air terminals greater than 24” in height shall be braced.
• Air terminals shall be placed within 2’ of roof ridge ends or within 2’ of outside edges or corners on flat roofs.

2 Interconnecting Conductors

The function of the conductors is to provide an electrical path from the air terminals safely to ground. Some of the key requirements relevant to residential homes are stated below:

• No less than two down conductors shall be provided from the air terminal system to the grounding system. These down conductors from the roof to ground level shall be installed at opposite ends of the structure, and shall be required at least every 100’ of outer perimeter of the home.
• There must be at least two conductor paths to ground for each air terminal.
• Conductors should be located at or near the perimeter of the structure.
• All roof top metallic objects (i.e. antennae, gutters, vent) should be bonded to the conductor system.
• The conductor can be either copper or aluminum and must be UL® listed for the application of a lightning conductor.

3 Protection of Electrical Equipment within the Home

A more common and regular threat exists to your electrical equipment within the home due to damage from electrical power surges. Although lightning is the most spectacular form of energy that can damage your valuable household electrical equipment, its only one source of damage. Other sources include operation or switching of electrical equipment on the power network. Its important to note that lightning does not need to directly strike a power line or your home to result in damaged equipment within your home. A lightning strike several hundred feet away can induce a damaging surge into the electrical, telephone or other services entering your home, even to underground cables. The threat of electric surges to equipment within the home is real, with sensitive electronics now present in a range of equipment in the home including TVs, home entertainment systems, home office equipment, security alarm systems, air conditioning systems and most home appliances.

It is possible to provide protection against this threat by arranging a “whole house” surge protector to be installed within your home. The benefit of installing a hardwired surge protector on your electrical panel is that you can be assured all electrical equipment within your home is protected. The only additional protection steps required include installation of surge protector on your home telephone and cable TV service if applicable.

4 Grounding System

The function of the grounding electrodes (rods) is to provide a point for the lightning discharge to safely enter the ground. It typically consists of a copper bonded ground rod, driven into the ground, outside the perimeter line of the structure. WARNING: Care must be taken before driving any ground electrodes that no services exist in the ground beneath. A ground electrode, driven to a depth of 8 ft typically is required at the base of every down conductor. Some of the requirements for lightning protection grounding, relevant to residential homes, are stated below:

• Ground electrode shall be at least ½” diameter by 8’ long, copper bonded electrodes are recommended.
• If rocky soil, services underground, or other reasons prevent a vertical electrode from being driven, a horizontal conductor, buried at least 18” below the ground, and extend ing no less than 12’ away from the structure can be used.
• All grounding systems shall be interconnected using the same sized (copper) conductor that was used as the lightning conductor. These grounded systems include lightning protection, electrical service ground, telephone service ground bond, antenna system (i.e. satellite TV) grounds. Note the electrical and telephone grounds should (by code) already be bonded, however it is advisable to confirm this with a qualified technician.
• In a similar method to point c above, interconnecting bonds are required to all underground metallic piping systems. This Includes water piping, gas piping, underground conduits or well casings within 25’ of the home. In the case of metal pipe systems that are interconnected with a section of plastic pipe, or non conductive fixing (joint) this section of the pipe shall be bridged using a lightning sized conductor and purpose designed pipe bond.
• If all services are already bonded prior to the lightning protection being installed, it is only necessary to bond from the nearest lightning protection ground electrode to the water pipe system.