Fixit: Lightning rod is a good idea for unprotected house on hill

Q Our home is on a high hill, along a river with no trees nearby. Would lightning rods be a safety check on our home?

A generation or more ago, lightning rods were on many houses and barns. They seem to have disappeared, but the incidence of lightning has not changed. What is the explanation?

A Yes, lightning rods are a good idea for your house.

"Lightning rods are just as useful in diverting lightning from striking a building today as they were when Ben Franklin invented them in 1752," according to David Rhees, executive director of the Bakken Museum, a museum of electricity and magnetism in Minneapolis.

Although lightning isn't as serious a threat in Minnesota as in other areas, such as Florida or the foothills of the Rocky Mountains, most experts recommend some kind of coordinated lightning protection. In the situation you describe, it may be especially necessary.

One reason why lightning protection isn't as common as it once was is that insurance companies have changed their policies. In the early part of the past century, they allowed credits for lightning protection systems for some residential structures, particularly those remote from fire protection. Today, most insurers lump lightning losses with all fire losses.

Another reason is that some people believe that their home is grounded because their electrical system is. However, even houses with an electrical system ground, communication system ground, maybe a data system ground, and metallic piping systems (water, sewer, gas) that enter the ground, are not protected from lightning strike damage.

Lightning tries to get from its strike point -- normally a ridge, corner or edge of the roof line or to a projecting body -- to ground. It will follow the easiest path, which could be along metal piping, electrical wiring, even wallboard nails. If allowed to advance with no control mechanism through a structure, it may move from grounded system to grounded system, "jumping" or side-flashing through the house. When these various grounded systems are not intentionally interconnected or bonded together near grade, then the jumping can occur from a less suitable ground path (a poorly grounded water line) to a better path (the electric service ground).

Several contracting firms in Minnesota will supply and install lightning protection. Look in yellow-page directories, or check the Underwriters Laboratories website (www.ul.com/lightning). Remember, when hiring any contractor, practice due diligence. Check with the Better Business Bureau, get references and check them.

Includes information from National Lightning Safety Institute www.lightningsafety.com

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