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. Radius and mesh are set out per protection level in Table 2 of the standard:

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 Bbl (Buildings and Living Environment Decree; the Bouwbesluit before 2024), 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