ᐅ Is Lightning Protection Necessary for a New Build?

I have a follow-up question:

Can it generally be said that a lightning rod / lightning protection system on a timber frame house makes (no) sense?

What happens if lightning strikes the lightning rod / a grounded gutter? Can a fire still occur despite the lightning protection system?
Is the likelihood of a lightning strike higher if grounding is present?

Search for Dehn Blitzplaner; it contains all the information you need, including risk assessment, legal requirements, technical details, and more.

In my opinion, there is no simple answer. Years ago, we had a semi-detached house next to a large walnut tree that was significantly taller than all the neighboring houses, so we saw no need for a lightning rod. It took only three years before lightning struck the neighbor’s house, causing a fire in their roof structure and nearly destroying almost all our electrical appliances. Now we have been living for 20 years in a detached house equipped with a lightning conductor, and there hasn’t even been a single thunderstorm.

roestzwiee schrieb:

Is the likelihood of a lightning strike higher if grounding is present?

Even if that were the case, would your house then be protected… If the electric field strength is high enough to discharge as lightning, the lightning will probably strike the lightning rod rather than the neighbor’s house, assuming it is the same height. But lightning is not “attracted.”

roestzwiee schrieb:
My electrician explained to me that we need to ground the rain gutter and the exterior stainless steel chimney via the foundation earth electrode.

You will have to determine for yourself whether this electrician is among the approximately 20% of the profession who still hold a valid VDE subscription for electrical engineering trades. However, even with such a subscription, electricians are not necessarily lightning protection specialists, and where building regulations do not require a lightning protection system, there is no obligation to ground rain gutters or downspouts.

Nevertheless, it makes sense to design grounding systems so they can be used for a future lightning protection system, and to include connection tabs for a lightning protection system at minimal additional cost during the installation of the grounding system. In that case, the downspouts should also be connected to these tabs.

roestzwiee schrieb:
You can then also ground the solar system on the roof via the rain gutter. The argument is: In case of a lightning strike to the solar system or chimney, it is safer if the current is conducted outside the house.

Lightning currents use every path to earth. They distribute proportionally according to the inductive impedances of loop conductors, almost independently of cross-section, so the wishful thinking of directing all current outside the building—even with unusually lightning-current-capable connectors—cannot be fulfilled.

roestzwiee schrieb:
The company that installed the foundation slab was willing to route all connections through the foundation to the outside, but advised me to think carefully about it.

Search for "DIN 18014:2023-06" and check whether this company meets the requirements for installing and documenting grounding electrodes.

roestzwiee schrieb:
It was stated here that grounding is not necessary. On the contrary: if grounded, the system must be inspected regularly. If this is not done, it could cause trouble with the insurance in case of damage.

Lightning protection systems do not have an unlimited service life and must be maintained at defined intervals. Where a lightning protection system is installed, a functional grounding of the module supports according to DIN VDE 000-712 and DIN EN 62305-3 (VDE 0185-305-3, Supplement 5) is mandatory. Without a lightning protection system, contrary to common misconceptions, this is not required.

IF a functional grounding is installed, it must be laid according to the German standards directly adjacent to the photovoltaic cabling, which excludes the variant using the downspout.

See also the DEHN lightning protection planner. Even with at least two downconductors for a lightning protection system, functional grounding conductors of at least 6 mm² copper (with separation distance maintained) or 16 mm² copper (if separation distance is not maintained) are required by standards.

k-man2021 schrieb:

Even if that were the case, would your house be protected… if the electric field strength is high enough to discharge as lightning, the lightning is more likely to strike the lightning rod rather than the neighbor’s house if it is of the same height. But lightning is not “attracted.”

All previous studies on lightning damage have found NO increased local strike frequency due to lightning protection systems, photovoltaic arrays, and/or antenna installations of typical building heights.

Lightning tends to strike edges, corners, and especially points where there is a high concentration of field lines, which is why masts of terrestrial roof antennas often act as unintended strike receptors. The preferred lightning strike points can be determined quite accurately using the scientific lightning sphere method.

Direct strikes are objectively rare, and anyone who wants to protect their house or specific roof structures must equip them with separate strike receptors according to current technical standards. Direct grounding of antennas or photovoltaic systems with commendable external down conductors and the rarely found lightning current rated certified connectors and equipotential bonding systems with tension clamps cannot prevent partial lightning currents from coupling into the installations during direct strikes, which can destroy sensitive electronics.

*Dipol* schrieb:
A functional grounding of the module supports according to DIN VDE 0100-712 and DIN EN 62305-3 (VDE 0185-305-3, Supplement 5) is mandatory when a lightning protection system is installed, but without a lightning protection system, contrary to common misconceptions, it is not required.

Typo noticed too late, it should have been DIN VDE 0100-712.