Lightning protection for greenhouse complexes

Large glasshouse horticulture businesses combine an extensive, often hundreds of metres long, electrically connected steel skeleton with — certainly in the presence of a CHP (WKK) installation or an LPG/CO2 buffer — an elevated risk profile in the event of a lightning strike. NEN-EN-IEC 62305 is the standard that determines whether, and how, a lightning protection system (LPS) must be designed for such a complex.

NEN 1010 versus NEN-EN-IEC 62305: a separate standard

NEN 1010 (IEC 60364) governs the internal electrical installation, including surge protection (SPDs, §443/§534) as the interface with lightning protection. The design of external lightning protection — air-termination system, down-conductors, earthing system — however falls outside the scope of NEN 1010 and is governed by the separate standard series NEN-EN-IEC 62305 (recently revised, 2024 edition, replacing the 2011 edition).

Mandatory risk analysis (Part 2)

NEN-EN-IEC 62305-2 requires a formal risk analysis — comparable in setup to an RI&E — to establish whether an LPS is needed and, if so, which of the four protection levels (Lightning Protection Level, LPL I–IV) applies. LPL I offers the highest protection (intercepting approx. 99% of lightning strikes), LPL IV the lowest (approx. 84%). For a greenhouse complex, this analysis weighs, among other things, the size of the roof surface, the presence of hazardous substances (see the ATEX guide for CHP gas-engine rooms and CO2 storage) and the consequences of failure of climate control/lighting.

Rolling-sphere method and mesh spacing (Part 3)

Part 3 of the standard describes, among other things, the rolling-sphere method for determining the placement of air-termination conductors, with a mesh spacing ranging from 20 m (LPL I–II) to 60 m (LPL IV) radius, and a corresponding mesh network of 10 m (LPL I–II) to 20 m (LPL IV). On a continuous steel greenhouse structure with multiple sub-distribution boards, this raises specific design questions: the skeleton effectively functions as a large, electrically coherent conductive surface, and the standard requires that all metal parts capable of introducing a potential from outside the installation — including metal roof and facade structures — be connected to the main earthing busbar (see also the guide on main bonding).

Note: there is no lightning-protection interpretation, published by a Dutch authority, that is specific to greenhouses for the rolling-sphere method applied to a combined steel/glass structure at complex scale. The application described above is a general-principles application of the standard at greenhouse scale, not a literally citable greenhouse-specific clause.

Legal status

NEN-EN-IEC 62305 is not directly mandated via the Bouwbesluit (Building Decree), but its application is enforced in practice through the employer's general duty of care under the Working Conditions Act (Arbowet), and — in the presence of fire/explosion-hazardous installations such as an LPG or CO2 buffer — through fire-safety regulations that refer to the risk analysis of IEC 62305-2.

Common mistakes

1. Treating lightning protection as part of the regular NEN 1010 installation handover — the external LPS design falls under a separate standard (NEN-EN-IEC 62305) with its own risk-analysis process, not under the standard NEN 1010 handover test.
2. Not commissioning a formal risk analysis because SPDs are "already" present in the installation — internal surge protection (§443) protects the installation against indirect consequences, but does not replace the external risk analysis that determines whether an LPS itself is needed.
3. Adhering to a fixed mesh-spacing figure without determining the corresponding LPL from the risk analysis — the 20-60 m range depends directly on the protection level; without a risk analysis, any fixed figure is a guess.
4. Not factoring the presence of a CHP gas-engine room or CO2 buffer into the risk analysis — these significantly increase the consequence-risk of a lightning strike and should be explicitly included when determining the LPL.

Related

• Surge Protection (SPD) — §443
• ATEX & explosion-hazard zones
• Greenhouses and Horticultural Enterprises