Can solar panels cause roof fires?

The main contributing factors to solar panel flat roof fires is the electrical failure of components of the roof mounted Solar PV systems. Such failures can lead to electrical arcing[1] 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 roof mounted Solar PV modules that make up solar panel systems are typical locations where arcing may occur, leading to the outbreak of roof mounted Solar PV 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 roof mounted Solar 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 roof mounted Solar PV panels from the surface of the roof can influence how quickly a roof mounted Solar PV fire may spread. If they are too close to the roof surface, for example, the fire may spread more rapidly. The angle of the roof mounted Solar PV panels also plays a part in how hot spots can develop and the panels themselves could hinder efforts to extinguish the flames.

[1] Fault tree analysis of fires on rooftops with photovoltaic systems – Journal of Building Engineering 29 Nov 2021

How frequent are roof mounted Solar PV fires?

The risk of roof mounted Solar PV fires is relatively low, with analysis putting the annual fire incident rate at 28.9 fires per GW[2]. However, the rapid growth in renewable energy generation saw an increase in the roof mounted Solar 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 roof mounted Solar 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.

[2] 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 roof mounted Solar PV fires?

When fire-resistant roof boards are positioned below the waterproofing layer, and above the insulation, they can help mitigate the risk posed by roof mounted Solar PV 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 roof mounted Solar PV fires.

Georgia-Pacific manufactures a range of DensDeck® fire-resistant boards. DensDeck® Roof Board is classified as A1 in accordance with EN 13501-1 and non-combustible as described and tested in accordance with ASTM E136. 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.

If you would like to find out how DensDeck® Roof Boards can help mitigate the risk of a roof mounted Solar PV fire on your flat roof project, please contact us today for advice and support.