Should we install a lightning protection system?
July 6, 2008 1:09 PM   Subscribe

Residential Lightning Protection System: good idea or waste of money?

The more I research this, the more confused I become. Our house is already built and is on a low hill in West/Central Texas with nothing else around, so the recent thunderstorms are making me VERY nervous. We recently received a $4,300 estimate for a whole house Lightning Protection System for our 4,000+ sq ft house.

Some people say these systems actually attract lightning. Some say that it’s only worthwhile if you have a pricey commercial system. Some say it’s extremely rare for lightning to even hit a house (which I find hard to believe since lightning did strike my mom’s house and her brick chimney exploded into a million pieces).

I’m also unsure how much of an eyesore it will create on our exterior with the rods sticking out on the roof and the copper wires running along the exterior. (I have not been able to find a house in person to see what it would look like.)

We do have a whole house surge suppression and individual surge protection outlets which should help the electronics.....however I suppose my biggest fear is lightning taking a direct hit to the house and it catching on fire or having major structural damage.

Please help me make a decision!
posted by texas_blissful to Home & Garden (7 answers total)
 
It depends on what sort of house you have. If you have wood shingles that are unpainted and have grayed, it is almost invisible and looks great (not really great, but fine). If you have a different color it may stand out. The rods themselves are about half a foot long and the wires are grey metal mesh wires about the thickness of an extension cord. The system I saw is about 30 years old, and I don't know what new ones look like though (although they can't have changed much).
posted by ooklala at 1:47 PM on July 6, 2008


Whether it's based in superstition or tradition or common sense I can't say (I suspect a little of each), but where I come from you'd be considered insane to build a house in an exposed area with nothing else around. Particularly something like a 4000 square foot McMansion. Where I come from, only a tiny fraction of a house's exterior is made of wood - brick and plaster, with clay tile roofs being the norm. Doing so, in the opinion of most people, would only *guarantee* that lightning would strike the house.

Do you have trees surrounding your property that exceed your house in height? That would be a big factor for me in making this decision. I doubt that copper wires themselves attract electricity more than just functioning as an excellent conductor of it when nothing else is around.
posted by Dee Xtrovert at 2:02 PM on July 6, 2008


Does your homeowner's policy cover lightning damage? Any chance your premiums would go down if you installed this system?
posted by amtho at 2:44 PM on July 6, 2008


Presumably you already have insurance that will cover you in the event of a lightning strike. If it does and the lighting blows up your chimney it won't be the end of the world.

I wouldn't take advice from a lightning protection system salesman. They have the interest in a possible sale. Talk to a local weatherman or some other local expert attached to a university, maybe?
posted by JJ86 at 2:46 PM on July 6, 2008


Well, there was a lightning strike just a few hundred feet from my house last week, so I looked into it...

According to the National Lightning Safety Institute, the most lightning-prone places in the whole of the United States get not much more than about 10 strikes per square km per year. So if you lived in such a place, and your house hypothetically takes up 1000 square metres in lightning footprint area because of its electrically attractive stature, you'd have a 1% per year chance of it getting hit. Over 50 years, then, it'd have about a 48% chance of getting hit, that'd be my guess for the worst case.

More likely your chances of a direct hit would be less than that, but apparently there are 256000 insurance claims for residential lightning damage each year in the US, so it's not all that uncommon. The average claim is less than $4300.

... actually, the NLSI has a page on estimating the probability of lightning striking. They say only 0.5 lightning flashes per km square per year and expect to get hit once every 17 years, for example, but that's for some 45000 square metre facility with 32-meter-tall light poles, and it's a bit complicated.

Lightning flash density can vary quite a bit depending on the local geography, for instance some part of Pennsylvania appears to vary between 0.5 and 5, over one year anyway. Not as much relationship to elevation as you might guess.

Some people say these systems actually attract lightning.

Well, my intuition would be to avoid hiring those people as the house physicists. A lightning rod might attract the path of lightning towards itself from a few feet away, but you can not attract lightning all the way down from the sky so easily, unless maybe you did something to incur the wrath of Zeus.
posted by sfenders at 4:47 PM on July 6, 2008 [1 favorite]


You could have a whole house surge protector installed by an electrician for $500 to protect your electronics, and gamble on the house strike. The fact that your mother's house got hit says nothing about the odds of you getting hit. Personally, I can't imagine that I'd spend that kind of money to protect against something that is so unlikely. Your homeowners insurance will cover you, and I doubt you'll see anything near a big enough break on your insurance from installing the system to make the ROI positive. If it's worth $4300 to buy some peace of mind I guess go for it though.
posted by COD at 4:59 PM on July 6, 2008


Well, since lightning strikes are rare, it is hard to test theories. Wikipedia has a lot of stuff on it.

I agree that a little rod sticking out of your house isn't going to change lightning's mind when it decides to strike. But it might be enough to give the lightning that was going to strike anyway a path of least resistance along the side of the house instead of right through it.

As for dissipation, I tend to think it's possible. There must be *some* reason lightning takes the path it takes- whether these systems are the answer, however, I can't imagine one way or another. It stands to reason that having metal spikes on your roof, tied to the ground, would tend to make your house appear no different from the ground.

As COD says, lightning is more likely to cause a number of lesser tragedies rather than a direct hit to your house. Like hitting a neighbor's house and zipping up through the phone line or through the ground up into your electrical system and blowing out a TV. So lightning arrestors and the like might not be a bad idea in addition to a lightning rod.
posted by gjc at 6:17 PM on July 6, 2008


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