When Benjamin Franklin did his kite-key-and-cloud experiment on a stormy night in Philadelphia in the middle of the 18th century, it’s hard to imagine that such a simple yet extremely dangerous act would spark a debate regarding lightning rods that still crackles today.
The costs from lightning-strike damage have risen in recent years, not because of the number of houses getting hit, but rather due to the destruction of sensitive, big-ticket electronic components therein. Computers, audio-video equipment, telephone systems, even that new refrigerator with the LED readout are all susceptible to high currents, and it’s likely that your run-of-the-mill surge protector won’t do much when a lightning bolts zaps your house.
But take heart: Compared to centuries ago, when dishonest lightning-rod salesmen would prey on fear-stricken folks who had seen their homes destroyed by a strike, we now know more about lightning and how to protect against it. A properly installed and maintained lightning protection system, consisting of cables, connectors, air terminals (the industry-preferred term for the rooftop rods), and at least two grounding rods sunk deep into the earth, can save your house. And while there are still some questionable devices and practices, better products, certification programs for installers, and even breaks on your homeowner’s insurance all have helped clear up some of the controversies.
If you look to the rooftops of some period buildings, you can see a row of sentinel-like lightning rods—often adorned with glass balls—stationed along the ridge, on chimneys, or atop turrets. For the longest time it was thought that the balls, which are still available on reproduction rods and highly collectible as originals, were put there to repel lightning and to indicate that the lightning rods were functioning properly. In fact, the balls were purely decorative; lightning rods neither repel nor attract lightning.
To understand how lightning protection systems work, you need to know a little bit about what happens when you see that white-hot bolt blast from the sky. Think about what happens in the winter when you shuffle across the carpet to turn on the television: You reach out with your finger, and when you get close enough, a little spark jumps between your digit and the TV. Now imagine that you’re a cloud, and the television is a tree, a house, or the ground.
Lightning starts when rising and falling air within a thundercloud separates into positively and negatively charged particles. A cloud-to-ground lightning strike, which happens about 20 million times every year, begins when an invisible channel of negatively charged air moves from the cloud toward the positively charged earth. The lightning doesn’t care whether the positive point is a tree, a sailboat mast, or your chimney; all it wants is to get into the ground. A lightning rod system doesn’t repel or attract lightning; it merely facilitates that travel of electricity to the earth.
“A properly installed lightning protection system performs the simple yet invaluable task of providing a network of low-resistance paths for lightning current to follow in preference to other parts of the structure,” says Jennifer Morgan, principal of East Coast Lightning Equipment, one of the largest suppliers of protection products in the country.
So what “other parts of the structure” is Morgan referring to? Imagine a bolt of lightning hitting the chimney on a house without lightning rods. It blows off the top ten courses of bricks before arching to the roof ridge and shredding its way under the shingles, then blowing the rake board off the gable end before splintering and catching fire to the corner boards. Then it jumps to the earth and into the underground wire that leads down to the copper fixtures on the lamppost at the end of the driveway. Oh, and on its way down, it also made a few frantic side trips around the house and took out the stereo in the front parlor and the microwave in the kitchen. It also might have jumped to the power lines, knocking out some of your neighbor’s electronics. While it may sound far-fetched, horror stories like this abound.
If lightning sees an unprotected house as a complex grid of roads, avenues, alleyways, and side streets, it sees a house with a lightning protection system as an interstate highway. A lightning protection system is made from copper or aluminum components that are bolted together to form a continuous and highly conductive path from the high points on a house to copper rods or metal rings buried deep in the earth. If that lightning bolt had hit the chimney-mounted lightning rods instead, it would have traveled from the rod to a braided copper cable along the ridge, down the corner board and safely into an underground copper rod or ring.
A total protection system also requires that lightning arrestors be installed on all incoming lines, including electric, cable, and telephone. These protect lightning from destroying your electronics via power lines. Remember: Your house may have a protection system, but you also need to protect yourself from your neighbors who don’t.Underwriters Laboratories (UL)—the same company that approves everything from fire extinguishers to toaster ovens and provides the little labels you’ve seen on myriad products—has strict compliance regulations for all the parts of a lightning protection system. Heavy-gauge copper and aluminum rods, cables, and connectors keep the lightning on the interstate and prevent it from veering down a side street to start a fire on your roof or blow the clapboards off your sidewalls. Along with approving the individual parts of a system, UL and other governing organizations such as the Lightning Protection Institute (LPI) and the National Fire Protection Association (NFPA) have strict mandates about the installation of the parts.
Exacting standards ensure that all the components of a system, as well as all the other metal parts in a house, including gas lines, well casings, and underground water lines, are connected by an uninterrupted circuitry to several grounding points in the earth.
Because a lightning strike will immediately find any flaw in the circuitry of a protection system, usually with devastating results, it’s important to keep in mind the words of Judy Ackerman, cofounder of East Coast Lightning Equipment: “Partial protection is as good as no protection.”
Don’t Try This at Home
If you search around online, you’ll find several sites that will sell you almost everything you need to set up a lightning protection system on your house. What they can’t sell you is the peace of mind that you’ve done it right. Do you really want to test your first-time lightning rod project on a bolt that’s several hundred million volts and has a temperature upwards of 54,000 degrees Fahrenheit?
Rob Cooper, president of Associated Lightning Rod Co., has been installing lightning rods on buildings for more than 40 years. He says customers sometimes balk when he tells them that lightning protection can cost anywhere from $1,500 to $3,500, depending on the size of their home. But as he puts it, “For less than 1 percent of the cost of your house, you’re getting an awful lot of protection.”
When you contact an installer, ask to see his credentials. UL certifies installers—check ul.com/lightning for a list of qualified installers in your area. After a UL-certified installer finishes a job, a third party UL inspector will come to the site to make sure every thing is up to snuff, and issue a certificate stating the system’s compliance. On some older installations, you can still find a small, brass UL inspection plaque nailed to the wall, usually near where a cable is attached to a ground rod.
Inspect Your Gadgets
When my wife and I moved into our house several years ago, I was happy to see a row of lighting rods on the ridge. But when I looked more closely, I saw that the workers on a more recent re-roofing job had left several of the rods unattached, and they dangled by their cables. And then I noticed that the one of the braided cables was no longer connected to the ground rod.
Cooper says this is a common occurrence, and that if your house is ever re-roofed, it’s important to put into the contract that the contractor is responsible for contacting and paying a UL certified inspector to check out the lightning protection system after the roofing job is finished. He also suggests getting your system checked out after house painting and chimney work.
It’s also a good idea, he says, to get existing systems inspected on any old house you own or are considering purchasing. Chances are, even if the rods, cables, and grounds all check out on a system that’s more than 15 years old, it probably has inadequate surge arrestors for all the different utility lines that come into the house.
The old adage is true: You never know where lightning will strike. But when it does, it’s heartening to know that certified installers using approved products can protect you and your house.
Jefferson Kolle, a former restoration carpenter, lives in an old house in Connecticut.
Online exclusive: Learn more about vintage lightning rods and where to find them.Published in: Old-House Journal June/July 2010