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Lightning Risk Assessments: What You Need to Know

July 1, 2020

Though the National Electrical Code (NEC) and most local building codes do not require lightning protection, property owners and facility managers would benefit from installing lightning protection. Building managers and facility managers can conduct a lightning risk assessment to determine the potential hazards.

Reasons for Assessing a Building’s Lightning Risk

Lightning strikes 40 to 50 times per second worldwide, and insurance claims for lightning-damaged buildings total more than $5 billion annually in the United States. If your facility does not include a lightning protection system, then a strike by lightning can cause property damage and disrupt the facility’s operations.

Possible consequences of lightning striking an unprotected building include:

  • Lightning traveling through the walls, instantly turning any moisture into steam (this can result in a high-pressure explosion of concrete walls).
  • Lightning sparking fires.
  • Lightning damaging or destroying electronic devices/systems within the building.

Assessing a building’s lightning risk helps with making recommendations to building owners. A high lightning risk would likely advise for the installation of a lightning protection system to safeguard the people and the facility’s continued operations.

Factors That Affect Lightning Risk

National Fire Protection Association (NFPA) 780, “Standard for the Installation of Lightning Protection Systems,” covers lightning risk assessment in Annex L. The assessment factors include the building’s area, frequency of lightning strikes, construction type, occupancy, contents, and more. Simplified calculations of risk use the following variables, among others:

  • Equivalent collection area: The building rooftop’s area and the height of structures there impacts the lightning risk.
  • Lightning ground flash density: The annual number of flashes per kilometer squared can be obtained from a ground flash density map.
  • Surrounding structures: The location factor impacts the likelihood of a lightning strike. For example, is your building isolated on a hilltop? Is the building surrounded by trees or other structures taller than your building?
  • Contents of the building: One factor in assessing lightning risk considers the risk of damage to the structure and to the property contents.
  • Type of construction: A steel structure and a wooden building hold different risks for lightning strike and damage caused by lightning.

Which Facilities Should Consider Lightning Protection?

Since lightning isn’t selective about where it strikes, facility managers from any/all industries should consider implementing an LPS on their facility. Particular consideration should be given to buildings which:

  • Contain large crowds
  • Provide critical services
  • Hold explosive or flammable materials
  • Are historical structures or represent irreplaceable cultural heritage
  • Experience high lightning flash frequency, or
  • Are subject to regulatory or insurance requirements requiring lightning protection.

How to Assess Your Facility’s Lightning Risk

Want to determine the lightning risk of your facility? VFC is the industry leader in Facility Protection Systems, with over 30 years of experience in designing and implementing solutions to mitigate damages from lightning and transient currents. Contact us to speak to one of our experts today!