NFPA 780 risk assessment, screen to signed report
Lumex runs the complete Annex L procedure of NFPA 780-2026, the current edition, on Voltrace™, the Lumex risk engine: a quick screen first, then the detailed assessment when the numbers call for it, with every figure traced back to its clause.
NFPA 780-2026 is the Standard for the Installation of Lightning Protection Systems. Its risk assessment sits in Annex L, which is informative: it guides the decision to protect a structure and is not a requirement of the standard. Lumex runs the full Annex L procedure, not a shortcut, and shows the working behind every figure.
Annex L gives two ways to answer the same question. A quick screen settles the clear cases in moments. When the numbers are close, or the facility is one that should not be caught out by a shortcut, the detailed assessment works out four risks from eight components and judges each on its own. New to NFPA 780 itself? See how it compares with IEC 62305, then read on for how Lumex computes it.
Two methods, one annex
The screen decides fast. The detailed assessment goes deeper when the screen is not enough on its own.
The simplified screen
Compares the expected strikes to the structure per year, N_D, with a tolerable strike frequency N_C built from the structure's own coefficients. An LPS is recommended when N_D is higher than N_C, and optional when it is not.
The detailed assessment
Works out eight risk components from the structure and its connected services, then rolls them into four risks, R1 to R4, one for each kind of loss. Each risk is judged against its own tolerable value, never a single combined number.
What N_D and N_C are built from
Both sides of the comparison come from the standard's own coefficients, never a guess.
Ground strike-point density
Read from the Vaisala strike-density map. Where only the flash density is known, Lumex converts it to strike points on the ground, the density the 2026 edition asks for.
The structure's collection area
The equivalent area around the structure that attracts a strike, built from its dimensions, which turns the strike density into N_D, the expected strikes per year.
Construction, contents, occupancy, consequence
Four coefficients describing what the structure is built from, what it holds, who uses it and what a strike would cost. Together they set N_C, the tolerable strike frequency it is judged against.
A critical facility, a hospital, a fire station or a power plant among them, should be protected or carried through the detailed assessment whatever the screen shows. That clause applies on top of the screen, not instead of it.
Four kinds of loss, each with its own tolerable value
The detailed assessment never sums the risks into one verdict. Each kind of loss is compared with its own tolerable line, and a structure can fail on one while passing the rest.
R1 · life or injury
Loss of life or injury
Judged against a tolerable value of 1E-5 per year by default, the strictest of the four. The owner or the authority having jurisdiction may set a different value.
R2 · service
Loss of service
The risk that a strike interrupts a service the structure depends on, defaulting to a tolerable value of 1E-3 per year.
R3 · historical significance
Loss of historical significance
For a structure of historical or cultural value, judged against a default tolerable value of 1E-3 per year, the same default as loss of service.
R4 · economic value
Loss of economic value
The annex sets no default tolerable value here. Lumex still computes R4 and reports it, and judges it against a value only if the owner enters one.
Eight components, from the structure and its services
Every risk is built from these eight components, each a source of strikes paired with what it puts at stake.
| Component | Where the strike lands |
|---|---|
| R_A, R_B, R_C | A direct strike to the structure itself |
| R_M | A strike near the structure, not a direct hit |
| R_U, R_V, R_W | A direct strike to a connected service, summed per service |
| R_Z | A strike near a connected service, summed per service |
The four kinds of loss are built from whichever of these eight components apply to that loss. Nothing here is summed into one number Lumex compares against a single line: R1 to R4 stay apart, all the way to the verdict.
What goes into the document you sign
One assessment produces a report carrying the verdict, the simplified screen with its working, and the detailed assessment broken into the strikes to and near the structure, the risk components, the probabilities and shielding factors, and the loss factors behind each figure.
Where a proposed upgrade is worth checking, Lumex can show the risks with that protection in place alongside the risks as they stand today. The proposal is a Lumex feature, not a step of NFPA 780-2026, and it never changes the verdict, which always follows the protection actually in place.
A closing section states how the assessment was made, and every clause, equation and table the report cites is NFPA 780-2026. Lumex is an independent product and is not affiliated with or endorsed by the NFPA; the values shown here are illustrative, and the authoritative annex is defined in NFPA 780, available from the NFPA.
Lumi speeds the routine. Voltrace still owns every number
You just read that procedure, computed clause by clause. Lumi works around Voltrace to cut the busywork, with the signing engineer in control at every step.
Risk-driver analysis
Reads the completed assessment and shows which component drives each risk, so you know exactly where to act.
Drafted report narrative
Turns your computed figures into clear report prose you review, edit and approve before it is filed.
Ranked mitigation options
Suggests protection upgrades and shows their effect on each of R1 to R4, with the maths shown for every one.
Early fail flags
Flags a risk likely to exceed its tolerable value as you enter inputs, long before you reach the final verdict.
One engine among three
NFPA 780-2026 is one standard among three Lumex runs on Voltrace, alongside IEC 62305-2:2024 for international projects and AS 1768:2021 for Australia. Each engine follows its own standard's method, and a figure from one is never mixed with a figure from another. Final responsibility for every result rests with the signing engineer, and Lumex does not replace professional judgement or the published standard.
Building in an IEC region instead? See how an IEC 62305 assessment works, or read NFPA 780 vs IEC 62305 for how the two compare. Ready to run an assessment? see the full platform.
Lumex computes the method of the standard you choose, IEC 62305-2, AS 1768 or NFPA 780, and shows the working. It does not certify a structure. You may not issue or submit a Lumex output until a competent person, qualified where the structure is located, has reviewed the inputs and the result and signed it.
The tolerable risk in IEC 62305-2 is not a fixed constant. Clause 7.3 NOTE 1 gives RT = 1×10-5 per year as a representative value of tolerable risk and adds that another value may be set once the case has been investigated in detail. Printed p.12 then lets national or local regulations fix RT, the tolerable frequency of damage FT, and the Annex A, B, C and E calculation rules and parameter values. Every IEC 62305-2 assessment in Lumex states the jurisdiction it was computed under and the values that applied.