The presence of photovoltaic (PV) panels on a commercial flat roof not only increases fire risk but can also change the behaviour of a fire when it occurs, so it spreads faster and is harder to extinguish. Here, Ieuan Compton, International Strategic Marketing Manager on behalf Georgia-Pacific explains how to mitigate these risks by using roof cover boards to increase flat roof resiliency.
Electrical components automatically increase the risk of fire, and in the case of PV panels, analytics show us that for every GW of solar capacity installed, there will likely be 29 fires. Given that commercial solar deployment has increased by 42% year-on-year, it makes sense that the number of PV fires experienced could also be set to soar.
Risk doesn’t stop at a greater fire incidence rate, though. If a fire does occur, solar panels can make roof fires more difficult to detect, allowing greater time for the fire to spread before the alarm is raised. Even if a fire is detected quickly, it can spread much faster on a roof with PV panels compared to one without.
To work safely, firefighters need to disconnect building utilities. Because PV panels produce power in daylight, they remain ‘live’, hindering access to the roof, adding delays before firefighters can get safely into position to tackle the fire. The panels also shield areas of the roof, hampering firefighters’ attempts to extinguish flames and prevent them from spreading.
In addition, Towergate insurance brokers further highlight the fact that PV panel systems can increase the building’s fire load. This affects their estimated maximum loss for a site. They provide an example of the potential consequences if a fire were to break out on the roof above automatic sprinklers that protect the interior of the building. If the fire spreads to the inside of the building or across the roof, it may compromise the installed sprinkler protection and increase the cost of damages to the insurer.
How to mitigate against fire risk
The first step is to reduce the risk of electrical faults. Always choose a proven solar PV panel system design that has been tested to meet a variety of standards and performance benchmarks, as this helps to mitigate against the occurrence of electrical arcing, a leading cause of fires within PV panel roofs.
Consideration should be given to arranging panels in arrays, which should be separated by between 1m and 2m. This compartmentalises the roof, helping to stop fire spreading between the arrays.
The system must also be installed in line with the manufacturer’s guidelines, with particular attention paid to the angle of the PV panels and the ‘critical gap distance’, as both can affect the rate and spread of flame.
Increasing fire resiliency of the flat roof
For the architect and specifier, consideration should be paid to the roof build-up. A fire that penetrates the roof will result in greater loss and disruption than one that is extinguished on the rooftop. It’s for this reason that global insurers of commercial and industrial buildings, FM, believe the majority of losses are preventable. AXA go as far as stating ‘Do not install PV systems on combustible roofs’.
The fire performance of commercial flat roofs will be affected by the quality and robustness of each component used within the build-up, including the roof deck, insulation layer and waterproofing. It will also be affected by fixing methods deployed, any adhesives that are used, and material compatibility. However, there is another key component of roof build-up that can contribute to flat roof resiliency: the roof cover board.
Cover boards, such as DensDeck® Prime Roof Board, are installed above the insulation layer and below the waterproof layer. Specifiers should look for cover boards that feature non-combustible materials such as gypsum with a Euroclass A1 reaction to fire classification.
If a fire starts on the outside of the roof, the presence of a roof cover board can help reduce the rate of fire spread across the surface of the waterproofing layer. It also helps increase the fire resistance of the overall roof build-up, slowing down the rate of fire penetration into the building below. As a result, installing a cover board within the roof build-up can help increase the amount of time available to extinguish a fire, possibly limiting the damage and financial loss to a business.
For ease of specification, architects can choose roof assemblies that are ‘FM Approved’ by the testing arm of FM, many of which include roof cover boards to help increase their fire-resistant properties, making them ideal for use with PV panels.
The addition of PV panels on commercial flat roofs introduces critical fire risks that must not be overlooked. The good news is that by combining best practices in PV system design and installation with measures to improve the resiliency of a flat roof, such as the integration of non-combustible roof cover boards into the build-up, architects and specifiers can easily mitigate the risk.