Installing Whole House Lightning Protection | Ask This Old House

Ask This Old House landscape contractor Roger Cook travels to central Florida to install a lightning protection system

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Homeowners have a virtual truckload of questions for us on smaller projects, and we're ready to answer. Ask This Old House solves the steady stream of home improvement problems faced by our viewers—and we make house calls! Ask This Old House features some familiar faces from This Old House, including Kevin O'Connor, general contractor Tom Silva, plumbing and heating expert Richard Trethewey, and landscape contractor Roger Cook.

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Installing Whole House Lightning Protection | Ask This Old House

[Wanda_Jannette]

My father installed 4 rods himself right on top of the house, cable is through exterior too and grounded several feet below. We get a lot of lighting & T-Storms during summer. So, we're blessed, there has never been any issues.

[JP-rfpx]

Speaking as a retired electrical engineer;
When a lightning strike occurs, the bolt creates a path of ionized air from cloud to ground. That's why you see the flash. That path conducts really well. The idea is two fold. The rods on the roof will leak off charge from the air over the house so it doesn't build up there as much. That's why more than one rod on the roof. Hopefully it will hit your neighbors house or the tall tree nearby, or the utility pole on the street that is taller and has a grounded conductor.
Then if it does build up too much or too quickly and hits your house, , the ground wire will "guide" the ionized path to follow it to ground as it is the lowest resistance path. But that ionized air is several thousand degrees hot!
Conductor in attic is a very bad idea, should be on exterior. Sorry about that "wife acceptance factor".
I would drive the ground rod several feet from the house, not next to it. Several on 6ft centers would be even better. And I wouldn't tie it to the electrical service ground as that can be a path for the surge right back into your house wiring. And the lightning ground system should be better than your service panel ground anyway as it needs to handle thousands of volts, not just 120 or240 volt faults.

[nonyadamnbusiness]

Sometimes I think "This Old House" should be called something like "Numbskull Renovations". As if running a lightning rod ground cable through the attic wasn't bad enough, they screw it down to the pine framing with copper tabs. Then they don't mention the necessity of bonding the lightning rod ground to the electrical system ground. They've built a system to transfer lightning from outside to inside the house.

[dennismcandless]

But the cable inside the attic attached to bare framing. Wouldn't that cause a fire if you had a lightning strike.

[coleve]

What stops the threaded bolt on the roof from rusting out. Why is the through the roof bolt not copper or brass. Why change to steel when it does not have the same conductivity as brass or copper, I would have thought dissimilar metals so far apart on the noble scale would encourage electrolysis in damp conditions.

[coleve]

Notice no topography mentioned before hammering ground bar into ground. Ie checking for other utilities that may be buried

[villayatMuhammad]

Can I run the lightning protection naked copper wire through the attic and through the wall and cover it with the foam insulation. I read the 780 SPEC and according to it I can.. could you please verify my understanding as someone told me that, the heavy current when run trghough the conductor, may burn the trusses or foam insulation. My understanding is, teh copper wire will not get that hot when lightning current passes through in case of lightning strike. Appreciate your help and support.
Thanks
Villayat

[josephmauldin]

That is a great setup! I never thought about protecting my home like that. I have had lightening hit just a few feet away from the house a couple of times and it has really done some damage to everything inside.

[NSMike]

While lightning rods CAN ground a lightning strike, that's not the goal. Lightning rods ground the charge buildup that causes lightning strikes to happen in the first place.

[PlayRightParent]

When you put the rod into the ground, how do you know your not going to hit any utilities?

[jcusak]

Copper and brass is used for the whole install, then the main rod on the roof is connected with a piece of steel all thread. Doesn't seem to make sense, or am I wrong? @ 1:10

[jimh]

What size was the grounding conductor. (Cable)

[rolfsinkgraven]

Why inside? that sounds like a fire hazard too me if it strikes.

[robertotrinanes]

you should test the thermal resistivity of the grounding rod.

[SkillTK]

the video is interesting and informative, I've been installing lightning arrester across saudi arabia, the video didn't show how you connected the surge device in relation with the grounding and lightning aerial.

[Skammerd]

Was the electrician off today? Why's Roger there?

[rawmilkmike]

This used to happen to me when I changed the streetlight bulbs under transmission line. It's capacitive reactance.

[Cityboy]

Does the lightning rod also pull electrons from the air aswell???

[marriagepartnersministry]

Wouldnt it be better to run a thick copper wire up a tall tree right next to the home and ground that wire? It would be taller and would keep burning away from the home. If there isnt a tall tree close to the home then maybe a metal tower for a wind turbine or ham radio tower would be a good location for a lightning rod?

[KamenKr]

Well, if a lighting hits the rod, the copper cable will get hot and it can couse a fire because it has a close contact to the wood. Is this true?