Addressing solar PV fire risks: safety, prevention, and mitigation
Industry best practice, Building standards and regulations
Pictured: Bauder's Pinkhill Gate project.
The UK has witnessed an increase in fires associated with solar photovoltaic (PV) systems, raising concerns across industries and regulatory bodies.
High-profile incidents, such as the Poole Travelodge evacuation and the fire at Bristol’s Grade II-listed science museum, We The Curious, have highlighted potential risks. Data from the UK government indicates a significant rise in solar PV-related fires, with reported cases increasing from three in 2010 to 66 within the first half of 2023 alone.
Understanding the fire risk
While these incidents are concerning, the increase in fires correlates with the rapid expansion of rooftop solar PV installations, particularly as poorly-maintained systems age.
However, put into context, correctly installed and maintained roof mounted solar arrays are inherently low risk. A 2018 report by the BRE national solar centre found that there were less fires in the UK per unit installed caused by solar arrays than tumble dryers. That said, it is also the case that installing a solar array will both increase risk of a rooftop fire as well as change the fire performance of the roof system itself.
Despite the overall safety of solar PV, even a small percentage of failures can lead to numerous fires due to the scale of installations — approximately 1.7 million rooftop installations are now installed in the UK alone. This underscores the necessity for stringent fire prevention measures and industry-wide best practices.
The role of flat roofs in solar PV installation
Flat roofs are increasingly favoured for solar PV arrays due to their accessibility, minimal shading, ease of installation and maintenance and low visual impact. However, limited research, regulation and standards concerning the fire performance of roof-mounted solar PV systems mean it is vital that the industry does everything it can to prevent fires from occurring and mitigate the impact of those that do.
Prevention
There are various solutions a designer can consider that will reduce the chance of a solar array causing a rooftop fire. The two most important decisions a client can make to ensure their rooftop array is as safe as possible are:
- Contractor selection
Using an experienced, quality installer will ensure that the correct electrical standards are met, and that due care is taken over design and installation. - Ongoing maintenance
Regular maintenance will prevent minor issues becoming significant ones whilst ensuring maximum yields.
Pictured: Bauder's Noah's Ark Children's Hospice project
DC connections
Site-made solar connectors have often been found to be the biggest cause of rooftop solar fires. To minimise this risk, Viridian Solar has developed the Arcbox, a connector enclosure which has been proven to prevent electrical arcs from becoming electrical fires. We encourage all of our partner contractors to install Arcbox wherever there are site-made DC connections on the roof.
Mitigation
A 2022 report by the University of Edinburgh found that 33% of PV fire incidents are due to unknown or unrelated ignition sources, indicating that greater focus should be given to mitigate the consequences caused by PV-related fires.
As well as preventing and limiting the cause of rooftop fires, it is therefore vital to ensure that installing a roof mounted solar array does not create conditions where a rooftop fire would lead to unacceptable risk for the building or its occupants.
At the time of writing, there are currently no test standards or methodologies for evaluating the impact of fire on flat roof mounted solar arrays.
Bauder has therefore developed the following guidance for installation of our BauderSOLAR systems.
One of the following elements must be in place:
- A non-combustible deck, i.e. metal or concrete
- Non-combustible layer above the waterproofing:
- 50mm of stone ballast, or
- BauderGREEN substrate
- Bauder DensDeck® Prime ‘cover board’ installed between waterproofing membrane and insulation
Pictured: Bauder DensDeck® Prime
About Bauder DensDeck® Prime
One of the most promising advancements in fire risk mitigation is the introduction of non-combustible cover boards as a thermal break. Inspired by US standards, Bauder has recently launched Bauder DensDeck Prime cover board that acts as a protective layer between a building’s waterproofing and insulation. This innovation reduces fire penetration, through the introduction of a thermal barrier, preventing flames from reaching the deck and minimise any potential structural damage.
By containing fires above the cover board layer, the risk of internal damage and water infiltration from firefighting efforts is also reduced. Insurers, including Zurich and FM Global, are increasingly recognising the importance of cover boards as thermal barriers in fire prevention strategies, and their adoption is becoming increasingly prevalent.
The business and environmental cases for rooftop solar PV installations are now well understood. For commercial and public buildings, the introduction of a rooftop solar PV system is becoming, and should be, installed as standard, the only decision to make now is how to ensure we do not compromise building and occupant safety.
Contact us today about your photovoltaic project
Each project is unique in its requirements, and we have lots of resources and examples of our work available to help guide you. If you are looking for a solar PV solution for your new build or refurbishment project, then get in touch with our team to discuss your project’s individual needs.