Solar Panels and Fire Spread Over Pitched Roofs: What Recent Government Research Means for Building Owners
Solar photovoltaic panels are now a familiar sight on rooftops across Chester, the North West, and North Wales — on homes, care homes, schools, warehouses, and commercial premises. For most building owners, the installation makes straightforward commercial sense. A recent experimental study published by the Building Safety Regulator and the Health and Safety Executive suggests that the fire safety implications of those installations deserve rather more attention than they typically receive.
The rate of solar PV adoption has been substantial. According to insurer QBE, fires involving solar panels increased by around 60% over the two years to 2025, with UK fire services attending a solar panel fire approximately every two days. High-profile incidents have made the risks visible in a way that industry statistics alone rarely achieve — Bristol's St Michael's Hospital fire, footage of which is below, was one of several significant PV-related fires that drew wider attention to the issue last year.
For building owners and responsible persons, the question is not whether solar panels are worth having — that is primarily a commercial and environmental decision — but whether the fire safety implications of a rooftop PV installation have been properly understood and addressed. A study published in early 2026 by the Building Safety Regulator and HSE provides experimental evidence that bears directly on that question, and its findings are relevant to anyone responsible for a building with rooftop solar, whether recently installed or in place for some years. The full report is available from the government's publishing service.
What the BSR/HSE research examined
Historically, external fire spread across roofs has been assessed using standard roof classifications, which assign a performance rating to the roof covering based on its behaviour in standardised fire tests. These classifications — Broof(t4) being the highest, meaning negligible contribution to fire spread — were developed without reference to solar panels, and the research set out to establish whether the addition of PV arrays above the roof surface changes the fire behaviour that those classifications were designed to predict.
The tests used pitched residential roof constructions representative of common UK building stock, fitted with different types of PV panel and mounting arrangements, and observed how fire developed and spread once it reached roof level. The methodology was designed to reflect realistic scenarios — a fire breaking through a roof covering and encountering a PV array above it — rather than idealised laboratory conditions, which gives the findings practical relevance for building owners and assessors.
What the research found
The headline finding is that solar panels can materially change how fire spreads across a pitched roof, and that the extent of that change depends significantly on how the panels are constructed and mounted. This matters because it means that a roof which performs well in standard fire tests may behave quite differently once a PV array has been installed on it, and that the fire safety assumptions embedded in the original building design or assessment may no longer hold.
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1Panel backing material is significant
Panels with plastic backing were shown to support more sustained flame spread up the array, with fire travelling further and faster across the roof surface than tests without panels. Glass-backed panels performed considerably better, generally limiting fire spread to the area around the point of ignition. For building owners reviewing an existing installation or specifying a new one, the backing material of the panels is therefore a fire safety consideration, not merely a technical specification detail.
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2Roof classification alone is not sufficient
In several tests, even where the underlying roof covering carried a recognised fire performance classification, the addition of PV panels altered the fire behaviour in ways that the classification did not predict. Flames spread beneath the panel array and re-emerged above the roofline in some cases, undermining the assumption that a well-classified roof provides reliable protection against external fire spread once panels are present. This has direct implications for buildings where the roof classification was assessed before the PV installation was carried out.
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3Heat accumulation beneath arrays
The void between the roof covering and the underside of the panel array allows heat to accumulate, increasing thermal exposure to the roof materials compared with an unobstructed roof surface. This effect is relevant both during a fire originating elsewhere in the building and in scenarios where the panels themselves are the source of ignition, since it means the roof covering experiences higher temperatures for longer than standard fire tests would suggest.
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4Mounting system design influences behaviour
How the panels are mounted above the roof surface — the height of the gap, the spacing between panels, and the materials used in the racking system — all influence how fire spreads. Systems that minimise the void beneath panels and use non-combustible racking components performed better in the tests, suggesting that installation design is a fire safety variable, not purely a structural or aesthetic one.
An important caveat: the BSR and HSE are explicit that this research represents early experimental data forming part of a wider programme of work. It does not, in itself, establish new regulatory requirements or invalidate existing roof classifications. What it does is provide a credible evidence base for the proposition that PV installations change roof fire behaviour, and it is reasonable to expect that emerging guidance and regulatory expectations will reflect these findings as the research programme develops.
What this means for responsible persons
The practical implications of this research fall into several categories, depending on whether a building already has solar panels installed, is planning an installation, or is subject to a fire risk assessment that predates the panels going on.
Existing installations and fire risk assessment review
Where solar panels have been added to a building since its last fire risk assessment, this research reinforces the case for treating that installation as a material change warranting a review. Under the Regulatory Reform (Fire Safety) Order 2005, the responsible person is required to review the fire risk assessment when there is reason to believe it may no longer be valid, and the addition of a rooftop PV system — which the research now confirms can alter external fire spread behaviour — is a reasonable trigger for that review. The assessment should consider how the panels interact with the roof construction, the building's boundary distances and proximity to neighbouring properties, and the implications for fire spread routes.
New installations
For buildings where a solar installation is being planned, the research supports engaging with fire safety considerations at the specification stage rather than after installation. The choice of panel type — glass-backed rather than plastic-backed where practical — and the design of the mounting system are both relevant to fire performance and are considerably easier to influence before the panels go on than after. Where the building has sleeping risk, such as a care home, residential block, or hotel, or where it sits in close proximity to neighbouring buildings, this consideration carries additional weight.
Fire service access and electrical isolation
PV systems present specific challenges for firefighting operations that are independent of the roof spread question. Solar panels generate electrical current whenever they are exposed to light, which means they cannot be isolated simply by turning off the building's electrical supply, and crews working on or near a roof with live panels face an electrocution risk that affects tactical decisions. Emergency plans and building information packs for premises with rooftop PV should reflect this, and it is worth confirming with the installer that the system includes readily accessible isolation equipment and that its location is clearly marked.
Buildings covered by the Building Safety Act
For higher-risk residential buildings — those over 18 metres or seven storeys — the Building Safety Act 2022 imposes additional obligations around the management of building safety risks, and the responsible person's duty to keep the building safety case current extends to changes in the building's risk profile. A significant rooftop PV installation on a building in this category is likely to be a matter that the accountable person should consider in the context of their wider building safety obligations, not simply as a standalone fire risk assessment question.
How we approach solar PV in fire risk assessments
At Fletcher Risk, we assess buildings as they are actually used and configured, not as they were originally designed. Where solar panels are present we consider how they interact with the roof construction, the site layout, and neighbouring properties, and we reflect current evidence and emerging guidance in our recommendations. If your building in Chester, the North West, or North Wales has rooftop solar, or you are planning an installation and want to understand the fire safety implications before committing to a specification, please get in touch.
Has your fire risk assessment kept pace with your building?
We carry out fire risk assessments for buildings across Chester, the Wirral, Cheshire, North Wales, and the wider North West, including premises with rooftop solar PV installations.
This article is intended to provide general information on recent fire safety research relating to solar photovoltaic panels on pitched roofs. It does not constitute legal, design, or installation advice. Fire safety requirements vary depending on building type, construction, and use, and guidance in this area continues to develop. Building owners and responsible persons should seek competent professional advice specific to their premises. Fletcher Risk Management Ltd accepts no liability for decisions made on the basis of this content.
Understanding how a solar panel fire would impact your building and what mitigations must be in place is therefore important. A recent experimental study published by the Building Safety Regulator and the Health and Safety Executive examined fire spread over pitched roofs fitted with solar panels. While the research is technical in nature, the findings are relevant to anyone responsible for the safety of a building with rooftop PV. You can read the full report here.
Why This Research Matters
Historically, external fire spread across roofs has been assessed using standard roof classifications. However, solar panels introduce additional materials, voids and fixing systems above the roof surface. This research set out to understand how those additions can affect fire development and flame spread. The tests focused on pitched residential roof constructions fitted with different types of PV panels and mounting arrangements, observing how fire behaved once it reached roof level.
What the study found
The research showed that solar panels can change how fire spreads across a pitched roof, and that not all systems behave in the same way. Key observations included:
Panel construction matters
Plastic-backed PV panels were shown to support more sustained flame spread up the array. In contrast, glass-backed panels generally limited fire spread, with flames remaining closer to the point of ignition.
Roof performance alone is not the full picture
Even where the underlying roof covering achieved a recognised fire performance classification, the addition of PV panels altered the fire behaviour. In some tests, flames spread beneath the panels and re-emerged above the roofline.
Heat can become trapped beneath arrays
The space between the roof covering and the solar panels allowed heat to build up, increasing thermal exposure to roof materials compared with a roof without PV.
It is important to note that this research represents early experimental data and forms part of a wider programme of research. However, the direction of travel is clear: from a fire safety and compliance perspective, PV systems are no longer seen as neutral additions.
What This Means for You
This research reinforces several important points:
Solar panels should be considered within fire risk assessments
Where a building has rooftop PV, those panels form part of the external fire spread risk. They should be considered when assessing roof construction, boundary distances, proximity to neighbouring buildings and potential fire spread routes.
Specification and installation are critical
The fire performance of a PV installation is influenced by panel type, backing materials, mounting systems and how the array interacts with the roof covering beneath. Competent design and accredited installation are essential, particularly on residential buildings or premises with sleeping risk.
Existing buildings may need review
Where solar panels have been added since the last fire risk assessment, this may represent a material change. In some cases, a review of the building’s fire risk assessment is appropriate to ensure the risks introduced by the installation have been properly considered.
Fire service access and response should not be overlooked
PV systems can affect firefighting tactics, particularly roof access and electrical isolation. These practical considerations should be reflected in emergency planning and building information, especially for larger or more complex sites.
Looking Ahead
This research will inform future guidance and regulatory expectations. While it does not mean that solar panels are unsafe, it does underline that they are a fire safety consideration that must be addressed properly rather than assumed to be benign. As buildings evolve, fire risk assessments must evolve with them.
How Fletcher Risk Can Help
At Fletcher Risk, we assess buildings as they are actually used, not as they were originally designed. Where solar panels are present, we consider how they interact with the roof, the wider site and neighbouring properties, and we provide clear, proportionate advice aligned with current evidence and emerging guidance. If your building in Chester, the North West or North Wales has rooftop solar, or you are planning an installation, we would be happy to advise on whether your fire risk assessment needs review and what practical steps may be appropriate.
Please contact us today to discuss your building and arrange a fire risk assessment.
Disclaimer
This article is intended to provide general information on recent fire safety research relating to solar photovoltaic panels. It does not constitute legal, design or installation advice. Fire safety requirements vary depending on building type, construction and use, and guidance continues to evolve. Building owners and Responsible Persons should seek competent professional advice specific to their premises.
© Fletcher Risk Team - 30 January 2026