Solar Panel Fire Rating Calculator

How to use this calculator

The tool combines the module fire test result (IEC 61730-2 §10.20) with the roof covering classification (BS EN 13501-5 Broof or BS 476-3) and returns the system fire class used by UK building control. It also flags whether the pitch triggers the MCS 020 access strip requirement.

1. Module fire type — choose Type 1, Type 2 or unrated. Modern modules certified to IEC 61730-2 are Type 1 by default; legacy installs (pre-2018) may be Type 2 or untested. The MCS Installation Standard now requires Type 1 on all new domestic installs in conservation areas.
2. Roof covering class — concrete and clay tile, slate and bituminous shingle achieve Broof(t1) or higher. Profiled metal sheet (Tata Steel Colorcoat HPS200, Kingspan KS1000RW) is typically Broof(t2) untreated, Broof(t3) with FR coating. Untreated wood shake (rare in UK new-build but common on listed buildings) is Croof and not accepted by most insurers for PV.
3. Mounting type — stand-off systems (Schletter Rapid 2+, Renusol VarioSole, K2 SingleRail) maintain ≥100 mm clearance and the underlying roof rating. Direct-fix to deck (uncommon in UK) drops the rating one class. Integrated (in-roof) systems like GSE In-Roof, ViridianSolar Clearline, Easy Roof Evolution are treated as BIPV — they replace the roof and inherit the module’s reaction-to-fire rating.
4. Roof pitch — pitches above 10 degrees trigger the MCS 020 access strip requirement (600 mm clear path on each roof plane).
5. Building type — dwellinghouses follow Approved Document B Volume 1; flats above 18 m and non-domestic buildings follow Volume 2 (much stricter A2-s1, d0 within 1 m of boundary).

The system fire class matrix

The calculator implements the IEC 61730-2 §10.20 + EN 13501-5 lookup used by LPCB Red Book and MCS 020:

A Type 1 module on a Broof(t4) tile roof gives system Class A — required by RSA, Aviva and Allianz for new PV installs in semi-detached, terraced and listed buildings since 2024. A Type 2 module on the same roof caps at Class B. The system rating is what your insurer and building control will record.

Why the system class matters in the UK insurance market

UK home insurance underwriters tightened PV terms significantly after the 2019 Notting Hill fire (cause: arc-fault in DC string, £2.4 million claim) and the 2023 Birmingham PV warehouse fire (Class C metal roof, BIPV laminates, total loss £18 million). Aviva, Direct Line, RSA, Allianz, Zurich and AXA all introduced PV-specific underwriting questions in the 2024–2025 renewal cycle:

• Aviva HomeSure 2025: requires MCS 020 declaration and system Broof(t4) for any property in a conservation area.
• Direct Line Home Plus: surcharges PV installs by £30–£80 per year unless the installer confirms system Class A and AFDD protection.
• RSA / Royal & Sun Alliance: declines new business on terraced houses with PV unless the array is set back ≥600 mm from party walls.
• Allianz Personal Property: requires fire-resistant boundary modules (EN 13501-1 A2-s1, d0) within 1 m of any party wall.

For commercial PV the FM Global UK & Europe office requires Class A roofs and Type 1 modules under PLP DS 1-15. Loss frequency on UK commercial PV (per Solar Energy UK 2024 sector report) ran 0.05 events per MW-year on Type 1 + Class A vs. 0.21 events on Type 2 + Class B — a 4× delta consistent with US data.

Code adoption across the four nations

• England: Approved Document B 2022 + Building Safety Act 2022 — A2-s1, d0 within 1 m of boundary for any building >11 m. PAS 63100:2024 for batteries.
• Wales: Building Regulations Approved Document B (Wales) 2022 — broadly aligned with England but separate amendment cycle.
• Scotland: Technical Handbook Section 2 (Fire) — uses EN 13501-5 directly, Broof(t1) minimum for dwellings, Broof(t4) for high-rise.
• Northern Ireland: Technical Booklet E (Fire safety) — follows Approved Document B with NI-specific amendments.

The MCS Installation Standard is recognised across all four nations and is the practical reference for SEG-eligible grid-connect installs.

Access strip and isolator requirements

Under MCS 020 and BS 7671:2018 Amendment 2 (2022) Section 712, every domestic PV install must include:

• 600 mm clear access strip from eave to ridge on each roof plane (waived only on solar tiles / fully integrated BIPV).
• Marked DC isolator within 1 m of the inverter, accessible without tools.
• AFDD (Arc Fault Detection Device) protection on every DC string per Section 712.531.3.
• Clearly labelled rapid-shutdown enclosure adjacent to the consumer unit, visible to fire and rescue.
• A laminated single-line diagram inside the consumer unit cupboard showing PV polarity, isolator location and battery connection (if fitted).

These access requirements can reduce installable module count by 10–18 percent on typical UK pitched roofs — most installers compensate by specifying 400–450 W modules. For a typical 4 kW domestic install the loss is one to two modules out of 10.

Real-world UK fire incidents

The 2019 Notting Hill fire (W11, Aviva claim £2.4 million) is the canonical UK case — root cause was a DC connector arc on a Type 2 module without AFDD. The 2023 Wickes warehouse Birmingham incident (total loss £18 million) involved Class C profiled metal roof with BIPV laminates that lacked the EN 13501-5 Broof(t4) certification. The Solar Energy UK 2024 sector fire report documents 31 PV-related fires in the UK between 2018 and 2024, with 87 percent attributed to DC connectors or string-level arcing on Type 2 modules.

See the solar panel hail resistance calculator for the impact-resistance counterpart — hail is rare in UK but increasingly relevant in Midlands convective storms (2022 Birmingham hailstorm caused 200+ modules to fail single-ply EPDM roofs). Both fire and impact ratings are checked at the same MCS 020 commissioning stage.

Practical guidance for UK installers

• Specify Type 1 modules from MCS Approved Product List — the MCS APL filters modules by IEC 61730 Type 1 certification automatically.
• Use Broof(t4)-certified roofs in conservation areas — most concrete tile (Sandtoft, Marley, Redland) and clay tile (Dreadnought, Imerys) products are already Broof(t4); ask for the EN 13501-5 test certificate.
• Avoid direct-fix to bituminous felt — drops the system rating to Class C and voids most modern insurance policies.
• Document the system class on the MCS commissioning certificate — the homeowner will need this for insurance renewal and for any future sale (RICS Home Report queries PV class since 2024).

Cost implications

Premium Type 1 modules (Q.CELLS Q.TRON M-G2.7+, JA Solar DeepBlue 4.0 GG, Trina Vertex S+) carry a £35–£55 per module premium over commodity Type 2 modules — roughly £350–£550 on a 10-module 4 kW domestic install. For a typical £8,500–£11,000 install the upgrade is 4–6 percent of project cost. Compared to the £1,500–£3,000 surcharge most insurers apply for Type 2 installs over a five-year policy term, the upgrade pays for itself in two to three years.

For deeper coverage of warranty and degradation interplay see the solar panel warranty calculator — workmanship warranties do not cover fire damage, so the system fire class is the only protection that travels with the asset.

Sources

• BS EN 13501-5:2016 — Fire classification of construction products and building elements (roof tests)
• BS 476-3:2004 — Fire tests on building materials and structures, external exposure to roofs
• Approved Document B (Fire safety) 2022 — Volume 1 (Dwellinghouses) + Volume 2 (Buildings other than dwellinghouses)
• MCS 020 (2024) — Solar PV Standard for fire safety
• BS 7671:2018 Amendment 2 (2022) Section 712 — Solar photovoltaic power supply systems
• LPCB RC62 / RC59 — Recommendations for fire safety design of buildings
• PAS 63100:2024 — Electrical installations — Protection against fire of battery energy storage systems
• Solar Energy UK 2024 Sector Report — Fire incident statistics