About Metal Roofs: Do They Attract Lightning?

Metal Roofs Aren’t What They Used to Be

What comes to mind when you think of metal roofing? If you’re like a lot of people, the image goes hand in hand with utilitarian storage buildings in lackluster industrial parks. Today’s modern construction, however, has greatly improved the look of metal roofs, so much so, that many homes and well-appointed commercial structures include metal roofing in their design.

But Don’t They Attract Lightning Strikes?

Cloud to ground lightning, the most dangerous to humans and property, is a sudden and intense electrostatic discharge between a cloud and the ground. Today’s metal roofs are attractive, but only to the eye. In fact, no type of roofing material attracts lightning more than another. Instead, lightning is attracted to the highest objects in an area and to structures that cover a greater mass. There’s a good reason why people clear a golf course when there is threat of lightning!

Metal Roofs Can Actually Be Safer

Developers often choose metal roof designs for their financial benefits. They are more durable, weather resistant, and energy efficient than traditional wood shakes or asphalt shingles. However, they are also more resistant to fire.

Steel and copper are good conductors and if struck by lightning will quickly send the electricity through the structure to the ground. Metal is also non-combustible and will not catch fire. Wood shakes, asphalt shingles and other traditional roofing materials, on the other hand, are flammable and have a far greater risk of catching fire.

Lightning Protection Systems

Because lightning is attracted to the highest points in an area, with the exception of city skyscrapers and other tall buildings, building roofs are not as likely to be struck by lightning. Instead, electrical wires, telephone poles, and trees tend to be targets. However, if a metal roof is struck, the damage from the impact will generally be mitigated when the electricity is spread across the roof’s mass.

According to the National Fire Protection Association (NFPA), during the five-year period from 2007 to 2011, firefighters responded to an average of 22,600 fires resulting from lightning strikes each year. The NFPA offers a risk assessment calculator for determining whether installing a lightning protection system might be warranted. Considerations are for the height of trees and structures in the immediate vicinity, the topography of a building’s location, the roofing material (metal is deemed safer), structure contents and occupancy, and what the consequences might be to continued services and the environment.

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