lightning rods are there to take lightning hits!
lightning rods are there to take lightning hits!
For best understanding why grounding the metal roof is a bad idea, google lightning protect methods and study up on it... You will find grounding the metal roof is just like moving the earth up HIGHER in the sky and so will indeed attract a lightning hit - lightning will go for the highest grounded point.....
On the other hand, a lightning rod is a special device made with as sharp a POINT on its vertical end as possible. this point DISCHARGES the static build up in the air and runs that static to ground thru the bonding wire. this eliminates the voltage difference between that point in space and the clouds with the lightning, thus eliminating the ionization of the air and thus preventing the strike in the first place. these rods are not there to take lightning HITs, just to discharge the voltage so it wont happen to begin with. You may have seen this in action on high radio towers where they have a pointed discharge rod attached then to a large metal sphere - when the static builds enough you can get lucky and watch the ball shooting off lightning into the air as it discharges like a whatchamacall it - vandegraff - thingy.
LOTS of difference between these two things!
Now if you want to talk about adding lightning rods to the highest points of the metal roof and bonding THEM to ground, now your on the right path....just like the 1920 metal roof barns of old....
that said, anyone with a metal tower for their ham radio antennas should have at the highest point a sharply pointed metal rod to discharge the static and prevent the antenna from attracting lightning. I have not had a lightning strike on my towers in the last 40 years - they have always had a sharp pointed grounded metal thing on the top *(usually in the form of a 5/8 wave 2 meter antenna).
oops: left out the NOT in title but edit won't let me add it....
