METAL MYTH #1: METAL ROOFS ATTRACT LIGHTNING
When you start talking to your friends and family about your new metal roof, inevitably someone will gasp and say, “Don’t you know that your metal roof attracts lightning!” They might tell you that, unless you’re trying to power the Delorean and you need your building to light up like the Clock Tower in Back to the Future, you should avoid a metal roof.
Did the Clock Tower have a metal roof? Probably not. Source giphy.com
First, we need a basic understanding of lightning. The Metal Construction Association describes it as the “flow of electrical current between earth and sky.” The brightest part of the strike, the flash, happens when electrons from the earth rush up to the sky along a path of ionization. Basically, lighting isn’t interested in your metal roof. It’s only interested in connecting negatively charged electrons with the earth’s positively charged electrons as fast as possible.
It’s impossible to predict exactly where lightning will strike, but topography is a much better indicator of a strike than building materials. Lightning is more likely to strike mountain tops and tall objects. It’s looking for the path of least resistance, so it’s drawn to whatever is closest to the sky. If you build your home on a mountain top or cliff edge, you may be more susceptible to strikes.
If your house is located in the mountains it may be more likely to field a lightning strike.
The size of your building and proximity of your building to taller structures are two more indicators. If you’re going to build yourself a skyscraper in the middle of the planes, it doesn’t matter what building material you use. Taller and larger buildings are more likely to be struck than surrounding smaller buildings. If you have a small house close to that huge structure your risk is reduced.
METAL IS YOUR BEST PROTECTION
While metal doesn’t increase the risk of a lightning strike, it does help reduce the impact. Remember, lighting is negatively charged electrons looking for the path of least resistance to the earth’s positively charged electrons. Thanks to middle school, we know that metal is a great conductor of electricity. When lightning strikes a metal roof it’s conducted away fast, toward the ground or another nearby conductor.
Metal is also a non-combustible material. Lightning produces intense heat, and often this heat can cause fires on the roof or inside the house. A metal roof can protect your house from both the heat of the lightning strike and the electrical current.
A metal roof can protect your home from lightning damage better than other building materials.
In fact, the Metal Construction Association says, “Because metal roofing is both an electrical conductor and a noncombustible material, the risks associated with its use and behavior during a lightning event make it the most desirable construction available.”
While metal roofing can keep you safer during a lightning strike, your property can still be damaged. If you live in an area prone to electrical storms or own expensive electrical equipment you should consider a lightning protection system, which creates a consistent connection between earth and sky.
From what we understand about lightning, it’s clear that metal roofing is no more likely to attract lightning than other materials. Metal roofing is the best material you can consider. The next time Aunt Marge claims your metal roof is going to light you up like a christmas tree, you can set her straight with this myth-busting knowledge.
If you have more questions about metal roofing and lightning, please send us an email or give us a call. We're happy to answer all your questions.
The Metal Construction Association Technical Resources: http://www.metalconstruction.org/index.php/education/tech_resources#lightning_metal_roofing
The Physics Classroom: