The energy transition in Europe is bringing about a growing adoption of photovoltaic systems, especially on rooftops. According to the European Union’s REPowerEU plan, new regulations in the Energy Performance of Buildings Directive (EPBD) are accelerating the integration of photovoltaic panels on all public, commercial and, soon, residential buildings. However, this rapid transformation poses significant challenges in terms of fire safety, especially when these systems are installed on flat roofs.
A detailed guide on the fire risks of PV systems, developed within the FRISSBE-ZAG Fire Safety Guideline (2024), highlights the dual threat posed by these installations: an increased probability of ignition and an amplified fire propagation dynamics.
This article analyzes the fire behavior of PV systems on rooftops, proposes laboratory-tested risk reduction solutions, and presents biosolar roofs as a resilient and fire-safe solution.
Fire risks generated by photovoltaic systems
Electrical failures in PV systems can occur due to electrical arcs, faulty connectors, insulation degradation or incorrect installation. A 2022 analysis estimates an average of 29 fires per GW installed per year. With hundreds of GW projected to be installed in the EU, tens of thousands of PV roof-related fires could occur annually.
Moreover, PV panels influence fire dynamics. The geometry, materials and mounting systems can create “wind tunnels” that accelerate fire spread. Tests show that the type of insulation used under the panels influences spread much more than the type of membrane or panel.
Several cases of fires caused by photovoltaic systems
Bakersfield, California, USA (April 2009)
Fire on the roof of a big-box store with 1,826 PV modules. Cause: ground fault.Mount Holly, North Carolina, USA (April 2011)
Fire on the roof of a plasterboard factory. Cause: grounding fault.Goch, Germany (2012)
Fire in a warehouse with an area of approximately 4,000 m². Cause: defect in the PV system.La Farge, Wisconsin, USA (May 2013)
Fire at the headquarters of an agricultural cooperative. The fire started indoors and spread to the attic. The sprinkler system was not effective. At some point, the metal roof became energized by the PV system, complicating the firefighters’ intervention. The fire lasted over 24 hours and the building was completely destroyed.Florence Township, New Jersey, USA (November 2013)
Fire on the roof of a 65,000 m² distribution warehouse with over 8,000 PV modules. Over 300 modules were affected. Due to early notification, the intervention was rapid and the fire did not spread to the building.Traiskirchen (Austria) (Zach, 2019)
Fire in an industrial complex where over 50 firefighters intervened to prevent the fire from spreading to other buildings.Bristol (United Kingdom) – We the Curious (Millen & Morgan, 2022)
The fire was caused by a bird hitting a panel. Since that incident, the building has been undergoing restoration due to damage caused by water used to extinguish the fire.McKesson, New Jersey (USA) (Goldman, 2023)
The fire spread quickly due to a large space between the clusters of photovoltaic panels.Halle, Belgium (Don Bosco School, 2025)
Fire on the roof of a school equipped with approx. 160 solar panels. Approximately 100 of them were destroyed. The possible causes of the fire were flammable roofing materials under the panels.
Technical factors and fire test data
A key finding of the tests is that non-flammable insulation – such as mineral wool or basalt wool – considerably reduces the thermal load and blocks the spread of flames. In contrast, systems with combustible insulation (PIR or EPS) have shown catastrophic failure modes, igniting within minutes of exposure to a localized fire source. For effective risk management, all elements must be tested as a complete system (panels, structure, membranes, insulation), according to EN 13501-5, UL 1703 or FM 4478 standards.
Complications for interventions and safety aspects
Once lit, PV roofs make it difficult for firefighters to intervene, due to the continuous electrical current active in daylight. Even after disconnection from the grid, DC cables can remain live. Systems above 30 kW require special emergency access protocols and quick shutdown functions.
To reduce risks, the guide recommends:
- Corridors of 1.2–1.5 meters
- Non-combustible buffer zones around skylights and HVAC systems
- Segmentation of PV installations to isolate vulnerable areas.
Green roofs as a fire reduction measure
Although initially viewed with skepticism, recent data confirms that well-designed green roofs are not flammable, and in fact improve fire resistance.
According to a 2020 study published in Buildings (MDPI): Extensive green roofs (substrate <15 cm and succulent plants such as Sedum) have thermal loads <10 MJ/m², due to the high moisture content in the soil and vegetation. In comparison, conventional bituminous membranes can reach 90 MJ/m², significantly increasing the risk of ignition. Another indicator, the critical flux at ignition (CFI), is much higher, >30 kW/m², for wet green roofs, compared to 10–15 kW/m² for dry synthetic membranes.
Safe green energy – with Biosolar systems
Did you know
that you can combine sustainability with maximum safety in the same photovoltaic system?
Biosolar roofs combine photovoltaic panels with the ecological and thermal benefits of green roofs:
- The green substrate acts as a heat absorber
- Vegetation reduces the accumulation of flammable materials
- Persistent moisture reduces the chances of ignition.
And, last but not least, through the cooling effect of vegetation, surface temperatures on the roof are significantly reduced (even 40 degrees lower), which results in increased performance of photovoltaic panels, by increasing energy production.
Key safety factors in biosolar systems:
- Use A1, non-flammable insulation (e.g. mineral wool);
- Install modular, tested systems compatible with green and photovoltaic components;
- Provide buffer zones of at least 30 cm and access routes for firefighters.
- Use substrate with low organic matter content (<20%), at least 10 cm thick
- Maintain humidity through sensors and automatic irrigation (constant humidity of 15–40%)
- Choose fire-resistant plants (for example succulent plants, which store water in their leaves, such as Sedum species).
On the other hand, an appropriate solution for roof safety can also be the choice of the type of panels.
A 2023 study (conducted by Over Easy Solar) shows that vertical bifacial PV panels, integrated into green roofs, reduce horizontal fire spread by 50% compared to inclined panels.
The Ecostratos Biosolar System is the smart solution for green roofs with photovoltaic panels, offering increased fire protection, due to the special mineral substrate and vegetation with a high level humidity.
- The substrate used has a low content of flammable materials and effectively retains moisture.
- Carefully selected low vegetation with increased water retention capacity contributes to a natural barrier against the spread of fire.
- The vegetation layer and growing medium help cool the roof surface, preventing the panels from overheating and contributing to high energy performance.
Choose a Biosolar green roof and transform your building into a safe, sustainable and energy-efficient space.
Protect your investment in renewable energy!
Choose smart. Choose Biosolar.
- FRISSBE-ZAG BAPV Fire Safety Guideline May 2024 (.pdf, 3,26 MB)
- A state-of-the-art review of fire safety of photovoltaic systems in buildings – ScienceDirect
- ARC Tech Talk Volume 8 – Fire Hazards of Photovoltaic systems
- 5 potential fire hazards and mitigation in photovoltaic systems – Solarity
- Photovoltaic fire safety: Comprehensive measures to mitigate fire risks
- Flammability Characteristics of Green Roofs – MDPI
- Fire Safety on Flat Roofs with Solar Panels: Why Vertical PV Panels Are Safer
- Fire damages PV system on school in Belgium – PV Magazine
