UK Study Urges Stronger Rooftop Solar Fire Standards After Heat-Flux Findings

A UK government-commissioned study has concluded that rooftop solar PV requires a more robust, system-level approach to fire safety, warning that current guidance does not fully reflect how PV arrays can change rooftop fire behaviour.

The research was carried out by Manchester-based fire and risk consultancy OFR Consultants and centred on a literature review examining whether rooftop PV alters fire dynamics, increases risks to roof structures, or complicates firefighting operations.

Across the experiments reviewed, the interaction between PV modules and roofing materials was found to raise heat exposure at the roof surface and accelerate fire spread, with reported incident heat flux values reaching almost 50 kW/m² when solar panels are installed. The study notes that factors such as panel elevation and tilt, mounting method, wind conditions, and spacing can materially influence fire dynamics.

A key takeaway is the identification of a “critical” gap height between the underside of PV modules and the roof surface, beyond which flame spread damage may be reduced. The review found that when the gap height falls below the critical range, flame spread can speed up by a factor of 38, driven by greater heat retention and re-radiation compared with comparable rooftop fires without PV. The report says this trend appears consistent across multiple independent medium- and large-scale studies.

OFR Consultants said the “critical gap” insight could inform mitigation options for both new and existing installations, but cautioned that it must be balanced against structural and environmental constraints such as wind loading and mechanical stability. The report also stresses that reported gap-height values are case-specific and should not be written into installation standards without further validation.

The study further argues that England’s current classification tests and building guidance do not fully capture PV-driven fire dynamics, because they typically do not reflect variations caused by PV geometry, installation practices, or whole-system behaviour. In the absence of a dedicated test method that better represents PV rooftop fire scenarios, the authors recommend prioritising measures to limit flame spread and roof penetration. Suggested steps include non-combustible roof coverings beneath PV arrays and clearer guidance on PV array configuration—such as minimum roof-to-module gap heights and appropriate spacing between panels.

The report adds that more research is needed to confirm which measures are essential and how effective they are, with an alternative pathway being the development of a roof fire test specifically designed to reflect the fire behaviour introduced by PV arrays.

The work forms part of the UK government’s real fires investigation project, which draws evidence from real-world incidents to assess how buildings perform in practice and to strengthen building safety outcomes.