We all know the saying, ‘lightning never strikes twice’, is a myth – after all, the Eiffel Tower gets hit multiple times every year. However, that’s about as far as the everyday folk’s knowledge will extend.
The natural electrical discharge follows the cloud-to-ground passage of a lightning bolt, which aims to find the path of least resistance to the Earth. Given that such bolts have to surge through miles of air before even reaching civilisation, the chances of them aiming within the vicinity of a household or any other structure is pretty marginal.
However, if lightning should happen to charge in your direction, then the variety of metallic routes most modern houses provide – from gas and water pipes to metal window frames – will provide convenient conductors for them to latch on to. Nearby pylon lines can also bring bolts within close proximity to residential areas.
So, which houses should pay particular attention to their safety – or in other words, when do buildings need lightning protection?
Naturally, it’s impossible to predict the exact location of all future bolts; at least not with today’s meteorological technology. That said, there is a method used by lightning specialists known as the ‘rolling sphere’ technique – this uses electro-geometric modelling to assess the risk of each building within a 50 metre radius. Any structure flagged up by this test, as well as taller buildings in general, would be advised to look into taking precautionary measures.
An individual risk assessment on a building is the most guaranteed way of knowing its current situation with regards to lightning-related risks. However, to stay on the safe side, an Early Streamer Emitting Device is a wise move for most property owners.
This lightning attractor works in a similar fashion to a conventional lightning rod. It triggers upward streamers which, when the electric field is particularly strong, begin to form. At this point they connect with a channel of ionised air that makes up the downward leader – a process which makes the bolt more likely to hit the device rather than the building. As far as lightning protection for buildings goes… it’s a cost-effective and sensible option.