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Lightning Risk Calculation Guide

Try the Online Lightning Risk Calculator

Does your Building Require Lightning Protection?

NFPA 780 is the North American standard for lightning protection systems (LPS). It contains “Simplified Risk Assessment” calculations to determine if an LPS is recommended for a building.

East Coast Lightning Equipment, Inc.’s online risk calculator automates the calculations to make it even easier. It also prepares a report you can present to the building owner.

For more detailed information, see User Guide for Lightning Risk Calculator

How to Use the Online Risk Calculator

  • Enter general project information.
demonstration of risk calculator
  • Sketch roof areas to show building’s general shape and size. Include large rooftop fixtures such as major pieces of equipment, antennas, etc. Enter height above grade for each building element.
demonstration of risk calculator
  • Click Map link to find lightning flash density.
map of lightning risk
  • Use drop-down boxes to enter the required information, then press “Calculate”.
demonstration of risk calculator
  • A two-page PDF report will be generated showing the data and sketch you entered plus the calculations. Based on NFPA criteria, the report will make one of the following statements:

risk determination results
For more information, see User Guide for Lightning Risk Calculator

Special Consideration

NFPA 780 states, “There are some cases where the need for protection should be given serious consideration regardless of the risk assessment. Examples are those applications where the following are factors:

  • Large crowds
  • Continuity of critical services
  • High lightning flash density
  • Tall isolated structure
  • Buildings containing explosive or flammable materials
  • Buildings containing irreplaceable cultural heritage

“Statutory, regulatory, and insurance requirements for the installation of a lightning protection system should take precedence over the results of a risk assessment.”

Discuss with Building Owner

Design professionals should discuss the risk assessment report with the building owner. If calculations or special considerations recommend a lightning protection system yet the owner decides against using it, the designer should get the decision in writing.

To weigh the benefits of an LPS against costs, see our cost study for preliminary cost guidelines. Or, contact ECLE to be put in touch with a certified lightning protection specialist in your area.

Go to the Lightning Risk Calculator