Fire safety for UK commercial solar installations
Government-commissioned research examines how rooftop solar affects fire dynamics, roof construction risks and firefighting operations. It aims to identify gaps in current guidance on how PV design and installation affect fire spread. The publication applies to England, and its findings and recommendations do not represent government policy.
Key takeaways
- UK commercial solar fire risks stem primarily from DC arcing, requiring strict adherence to BS 7671 wiring regulations and IET guidelines.
- Installing rapid shutdown switches and scheduling annual thermal imaging surveys mitigates DC isolator failure risks before thermal events occur.
- Demonstrating compliance with the Regulatory Reform (Fire Safety) Order 2005 protects commercial building insurance validity and limits corporate liability.
Typical system sizes
Retrofit rooftop (steel portal frame)
Standard compliance path: BRE 187 roof-cover classification, DC isolator at every string, rapid-shutdown-compatible inverters, arc-fault detection (AFCI) in the inverter.
Retrofit rooftop with insulation upgrade
Verify the finished cladding meets Broof(t4) with the panels installed. On combustible substrates specify an air-gap or non-combustible sub-layer per BRE 489.
Ground-mount / carport
Full DC compartmentalisation, ROC-monitored inverters, and standoff distance to any adjacent building per BRE 489.
Portfolio operator
Standardise on one manufacturer, one commissioning protocol and a single monitoring platform to spot arc-flash and insulation-resistance faults in real time.
What good specification looks like
Tier-1 panels, Tier-1 inverters with AFCI and rapid-shutdown, MC4-compatible connectors from a single manufacturer only (no cross-brand mating), roof-line DC isolators, monitored insulation-resistance testing every commissioning cycle, and thermographic scan at handover. This is the non-negotiable baseline on any commercial roof - refuse anything less.
FAQ
Do solar panels cause building fires?
Very rarely and almost always from installation defects - DC connectors not fully mated, isolator water ingress, unsupported cabling or roof-membrane damage. RISCAuthority statistics put annual UK solar-fire incidents in the low hundreds against ~1.5m installations. Following MCS 3007 and BRE 489 essentially eliminates the risk.
What is the DC isolator/rapid-shutdown expectation?
For new commercial installs, insurers routinely expect a firefighter-accessible DC isolator at the array as well as at the inverter, plus rapid-shutdown functionality on any building over four storeys or with public access - increasingly a de-facto standard on all commercial roofs.
What about the roof itself - does solar affect BS 8414 or Broof(t4)?
The roof-cover fire classification must remain compliant with the panels installed. On combustible substrates (some older single-ply and warm-roof systems) BRE 489 requires either a non-combustible sub-layer, air-gap detail or a re-tested roof buildup. A competent installer confirms this at survey.
Do we need arc-fault detection?
AFCI is a mandatory US requirement (NEC 2011+) and now standard in Tier-1 commercial inverters (SMA, Sungrow, Huawei, Fronius). We specify it on all UK commercial projects; it detects and disconnects a DC arc-fault typically in <2 seconds.
How should we brief the fire service and building insurer?
Ideally at design stage: supply a single-line diagram showing DC isolator locations, inverter positions and rapid-shutdown zones. Insurers increasingly want an MCS installation certificate plus workmanship-warranty proof at renewal; some now require an annual thermographic scan on installations over 250 kWp.
Review your project against fire-safety best practice
Sources for this guide
- https://www.gov.uk/government/organisations/department-for-energy-security-and-net-zero
- https://www.ofgem.gov.uk/energy-data-and-research
- https://mcscertified.com/
- https://www.gov.uk/guidance/check-if-you-can-claim-full-expensing-or-50-first-year-allowance
- https://solarenergyuk.org/resources/
- https://www.gov.uk/government/publications/fire-safety-solar-photovoltaic-panels-on-roofs
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