Solar Panel Fire Risk on Farm Buildings: What RC62 Asks (2026)

How PV fires start

RC62 is written for insurers and their clients, and its evidence base is worth quoting directly. Issues associated with installation have been identified as the largest single cause of PV fires. The 2017 Building Research Establishment study it cites found DC connectors, inverters and DC isolators accounted for 84% of PV-system-related fires. Product failure is the second largest cause: the IEC technical report on managing PV fire risk on buildings, IEC TR 63226:2021, found 33% of reviewed PV fires were caused by it. The practical reading for a farm is that the fire risk lives in the DC wiring and the plant room, not in the panels themselves, and that it is set on the day of installation.

The single most repeated instruction in the code is about connectors. IEC 62548:2016 and IEC 60364-7-712:2017 explicitly do not allow the connection of DC connectors from different manufacturers. RC62 asks for the connector the module manufacturer recommends, assembled with the correct crimp tool, exposed cable length and gland torque, and for spare compatible connectors to be kept on site so that a future repair does not reach for whatever is in the van. Connectors should lie horizontally, off the roof surface, on supported cable trays that drain, and interim inspections during installation should check that no cable is pinched under a module, a fault the code says can take several years to show itself.

Five hazards that belong to farm buildings

Grain dust. RC62 requires the ignition sources a PV installation introduces to be addressed under the Dangerous Substances and Explosive Atmospheres Regulations where a potentially explosive atmosphere may form, and its chosen example is agricultural grain storage barns at harvest time, where the dust could be explosive. If the inverters, isolators or distribution board are to sit in or next to a grain store, the DSEAR assessment and the integrity of any existing protected zones come before the layout drawing.

Rodents and livestock. Panels and wiring should be located where they are not likely to be damaged by rodents or, on ground-mounted systems, by sheep or cattle. Where that is a particular problem on agricultural premises, the code says cabling should be laid in secure and sealed trunking or ducts, sagging and hanging wires avoided, and where that is not possible, armoured anti-rodent PV cable used. A gnawed DC cable is an arc waiting for a dry day.

Birds, nests and debris. The gaps between panels and roof trap waste, foliage and bird and rodent nests, and moss and lichen grow under panels; the code describes these as hot-spots presenting ignition sources with additional fuel in direct contact with the PV system. Bird droppings get their own clause: they adhere whatever the pitch, cause partial shading on individual cells leading to hot spots, and such hot spots have been known to develop into faults leading to fire. The code states that insurers expect a regular cleaning programme for all commercial PV installations. Keeping birds out in the first place, and what the law says about nests already in place, is covered in bird proofing solar panels on farm buildings.

Combustible roofs. PV installations should be installed on non-combustible roofs meeting Class A1 or A2-s1,d0 to BS EN 13501-1, because fires involving combustible roofs spread quickly without the benefit of any protection installed inside the building. A new installation shall not lower the fire performance or classification of the roof, and where installation on a combustible or partly combustible roof is unavoidable, a fire-resistant covering should be applied. The code also notes the chimney effect beneath panels on pitched roofs, with heat radiated back onto the roof from the underside of the modules. Composite sandwich panels with a combustible core, common on newer livestock and packhouse buildings, are the farm case this clause is aimed at.

Straw, litter and hot work. Windblown litter and leaves must not be allowed to accumulate around or beneath panels, and no hot work such as welding or flame cutting should take place within or adjacent to the installation unless unavoidable, in which case it runs under a permit-to-work system. On a yard where a bale stack sits against the shed, that is a management rule as much as a design one.

Compartment walls and separation distances

Where a building is divided by a compartment or fire wall, RC62 adopts the CFPA-Europe guideline: components with combustible elements such as cables are not allowed to pass over the wall, and if that cannot be avoided they go in fire-resistant ducts; on the roof there should be a minimum distance of 2.5 m between the PV modules on each side of the wall. Where the potential for fire to spread across the boundary is low, meaning all roof elements are non-combustible and the modules have a low propensity to spread fire or produce burning droplets, a minimum 1.2 m separation on each side is recommended instead. Arrays should not traverse fire barriers at all, and all cabling should be sealed or contained so it cannot carry fire across them. High-density coverage that would stop firefighters venting the roof should be avoided.

The inverter and the DC side

Around 3% of the energy an inverter converts leaves as heat, so RC62 asks for its location to be considered carefully and for stored materials never to reduce its ventilation. Automatic fire detection should be installed in all areas inside buildings where inverters, isolators and distribution boards are located, and sprinklers should be considered for those areas. Separate DC isolators should be eliminated wherever possible in favour of inverters with integrated isolation, and the fire risk assessment should decide whether the inverter's arc-fault circuit interrupter is acceptable or a stand-alone one is needed. Internal DC cable runs should be as short as possible and mechanically protected where they cross occupied areas, because they can remain live when the AC is off. The equipment choices behind those clauses are on solar inverters for farm buildings.

What the law requires

• A fire risk assessment under the Regulatory Reform (Fire Safety) Order 2005, carried out and recorded by a competent person, and reviewed following the installation. The Fire Safety Act 2021 came into effect on 16 May 2022.
• Compliance with the Construction (Design and Management) Regulations 2015, which RC62 says apply to all PV installation projects, from small installations upwards, with client duties as well as contractor duties.
• A DSEAR assessment wherever a potentially explosive atmosphere may form, including the grain-store case above.
• Electrical compliance with BS 7671, and design to the IET Code of Practice for Grid-connected Solar Photovoltaic Systems and the MCS installation standard.
• The Building Regulations requirement that a new rooftop installation does not lower the fire performance of the roof.

What the insurer will expect

RC62 asks for the project to be discussed with the current or prospective insurer at the planning stage, and for ownership of the building and of the PV system to be determined, since they may not be the same party. NFU Mutual's published risk-management programme for roof-mounted PV sets out what a farm insurer is likely to look for: electrical work by a competent contractor on a register such as NICEIC or SELECT, a fixed-wiring inspection every five years on commercial premises, surge protection and consideration of lightning protection to BS EN 62305, a ventilated inverter housing with combustible materials kept away from it, the inverter and grid connection housed in or fixed to non-combustible construction, regular thermographic inspection, maintenance by an approved engineer with records kept, and for large commercial installations a fire alarm to BS 5839-1 with smoke or heat detectors in the inverter housing, arranged so that operation of the alarm automatically isolates the equipment. The full list, and what to have on file before the renewal call, is on solar panel insurance for farm buildings.

Maintenance that keeps the risk where it started

The code adopts the Solar Energy UK recommendation that commercial systems are inspected at least annually by a competent person, and refers maintenance to BS EN IEC 62446-2:2020, which states that the more often such inspections are performed the smaller is the risk of fire. Two low-cost tests matter most: routine insulation-resistance (Riso) testing, and string series-resistance testing, which the code says can identify strings at risk of overheating without scaffolding. Infrared thermography is described as a cost-effective way to determine module health, and drones of 250 g or less can carry the camera where roof access is unsafe. Cleaning should follow a risk assessment, with a scheduled programme on lower-pitched roofs, and the array should be inspected after any storm or extreme weather event. Live online monitoring is treated as a fire-safety tool because a failing string shows up in the data before it shows up as smoke.

Provisions for the fire and rescue service

A clear external route for high-reach and pumping appliances, with turning places as set out in Approved Document B, should be maintained to every building with roof-mounted PV. Information for firefighters should be held at the site entrance or gatehouse: the layout showing panels and control equipment, the location of the PV isolation switches and the main electrical intake, the alarm panel, any suppression system, hazardous substances on site, and water supplies. The presence of PV is not obvious from the ground, so a "PV on the roof" sign of at least 100 mm by 100 mm should be displayed at the consumer unit or supplier's cut-out. Where mandated by BS 7671 or required by the insurer, a fire-service switch in a prominent position should isolate the DC side remotely, be tested during routine maintenance, and sit well away from the arrays. Firefighters should be aware that panels keep producing DC from daylight and floodlights even with the AC isolated.

The figures on this page and where they come from

A pre-installation checklist for a farm roof

1. Roof construction: is it non-combustible to Class A1 or A2-s1,d0, and will the array leave its fire classification unchanged?
2. Compartment walls: where are they, and does the layout keep 2.5 m (or an assessed 1.2 m) clear on each side?
3. Grain, feed and chemical stores: has a DSEAR assessment covered the inverter and switchgear location?
4. Cable routes: sealed trunking or armoured cable where rodents or livestock can reach them; no cables over fire walls.
5. Inverters: non-combustible mounting, ventilation, detection, integrated DC isolation, arc-fault protection.
6. Firefighters: access route, information pack, "PV on the roof" sign, fire-service switch where required.
7. Maintenance: an annual inspection contract that includes Riso and string-resistance tests, cleaning and nest clearance, and inspection after storms.
8. Paperwork: the fire risk assessment reviewed after installation, and the insurer told before the quote is accepted.

Working at height on the roof itself is a separate duty: HSE lists non-reinforced fibre cement sheets as fragile irrespective of profile, and HSENI's guidance says nobody should stand on an unprotected fragile roof or work within two metres of one without barriers, and that solar installation is not short-duration work and needs scaffolding with a boarded platform and full edge protection. That sits with the roof decision on solar panels on asbestos cement farm roofs. For the planning side of the same project, see planning permission for solar on farm buildings; for the head-term guide, solar panels for farm buildings.