Can solar panels cause roof fires?
The main contributing factors to Solar panel flat roof fires is the electrical failure of components of the PV systems. Such failures can lead to electrical arcing where a current flows across an air gap by ionising the air. These high voltage electrical arcs are extremely hot (6,000+°C) and could cause combustion of surrounding materials on the roof including the waterproofing membrane.
The DC connectors, DC isolators, inverters and PV modules that make up solar panel systems are typical locations where arcing may occur, leading to the outbreak of solar panel roof fires. Arcing could be due to a variety of reasons, including poor installation, incorrect specification, build-up of contaminants on electrical contacts, or manufacturing faults within the equipment itself.
The PV panels themselves add a further complication as their presence may change the fire dynamic of a flat roof build up. The height of the PV panels from the surface of the roof can influence how quickly a solar panel roof fire may spread. If they are too close to the roof surface, for example, the fire may spread more rapidly. The angle of the PV panels also plays a part in how hot spots can develop and the panels themselves could hinder efforts to extinguish the flames.
 Fault tree analysis of fires on rooftops with photovoltaic systems – Journal of Building Engineering 29 Nov 2021
How frequent are solar panel roof fires?
The risk of solar panel roof fires is relatively low, with analysis putting the annual fire incident rate at 28.9 fires per GW. However, the rapid growth in renewable energy generation saw an increase in the PV market of over 22% in 2021. This brought the global capacity to 946 GW and could lead to an increase in the number of fires as the frequency of new solar roof installations rises.
This increase in the number of solar panel fires is recognised by insurance providers. They are now evaluating the risk that a fire will pose to the build-up of a flat roof under the PV panels and its ability to protect the building below. In some cases, previously insured roofs are being re-evaluated as posing too high a risk and can only continue to be covered
 Experimental Study of the Fire Dynamics in a Semi-enclosure Formed by Photovoltaic (PV) Installations on Flat Roof Constructions – Journal of Building Engineering 28 March 2022
How can the use of fire-resistant boards mitigate the risk posed by solar panel roof fires?
When fire-resistant roof boards are positioned below the waterproofing layer, and above the insulation, they can help mitigate the risk posed by solar panel roof fires by providing the roof with an extra layer of fire resistance. This can help to slow fire spread across the surface of the roof and help limit the extent of the damage caused to the building by solar panel roof fires.
Georgia-Pacific manufactures a range of DensDeck® fire-resistant boards. They have embedded non-combustible fibreglass mat facers that form the first line of defence against a fire and a gypsum core that contains crystalised water incorporated into its structure. In a fire, the energy from the heat vaporises the crystalised water to increase its fire-resistant properties.