The fire safety of pent roof systems is a topical issue. It is good that there is more attention for this, because we see that as a supplier we have been given too much freedom in this area in recent years.
In 2019, TNO published a report evaluating PV fires. It shows that connectors are the main cause of fire and that rooftop systems are overrepresented. There are connectors on the market that do click together, but because the inner workings are not standardised, different brands of plugs can cause excessive resistance. The plug can melt and an electric arc can occur. TNO has shown that the electric arc can reach a very high temperature, but is not a factor in the spread of the fire. An electric arc mainly functions as an igniter of other materials. Logically, the plug is located closer to combustible materials in a roof-in system and logically, therefore, you must take account of the material you use in a roof-in system.
In 2020, the Scope 12 directive was introduced in which various safety aspects are safeguarded. One important aspect is that it is stipulated that installers may not connect plugs of different brands together. This eliminates the main cause of solar fires. In addition, there are also rules on cable routing and inverter space, but no rules have yet been set for rooftop systems.
The lack of regulation is very annoying for insurers. They know that there is an increased risk, but TNO, BDA and Kiwa do not carry out any tests and have not drawn up any regulations. Logically, therefore, a pent roof system is scary to insure. It is therefore wise to contact your insurer before ordering to discuss your wishes.
Material useWe therefore carry out our own tests to check whether materials lying near the sunroof can ignite. These tests show that the condensation membrane poses a risk. It is unwise to use a condensation foil which does not comply with fire class B (self-extinguishing). Unfortunately, we also see that suppliers of sunroof systems occasionally make a mistake. Our test shows that HDPE (plastic) ignites when we simulate an electric arc. The HDPE burns and starts dripping, allowing the fire to spread easily. It is therefore unwise to use roofing systems that are made of HDPE or that have an HDPE underlay.
We have also tested various insulation boards. The roofing sheets we tested with fire class B (Unilin SW Element) and C (Kingspan Aero) do not appear to ignite. The roofing board we tested with fire class D (Unilin Renopir) did ignite. However, here too it is not the insulation material but the condensation foil (consisting of aluminium and paper) that continues to burn.
Naturally, all the materials that we apply and supply ourselves have also been tested. Perhaps our fire resistant fitting panels offer you additional possibilities, for example, to protect the house dividing wall against the spread of fire.
For a detailed explanation of our test, I refer you to our explanatory video which you can also find on this page.
Ventilation and cavityThe BiTile System is ventilated per panel and has a cavity of approximately 10 cm between the solar panel and the roofing material. Insurance companies are increasingly convinced that this contributes to fire safety. However, we have not been able to discover any effect.
Theoretically, a few degrees higher air temperature could cause a plug to melt just a little bit faster, but this effect is negligible. The resistance in the circuit causes a plug to melt. The idea that a roof covering can spontaneously catch fire from a slightly higher temperature is something we have not been able to observe in any case.
Our ample ventilation and cavity is primarily intended to increase the efficiency of the solar panels and to extend the life of the materials used.
Electric arc detectionTNO's findings are based on sunburns in 2018. At that time, the problem with
problem with the plugs and there were no inverters on the market yet with arc detection. In principle, an electric arc develops slowly. If the resistance in a connection is too high, the plug will melt and after about a quarter of an hour, the arc will be able to leave the plug. An electronic safety device therefore has sufficient time to detect the arc and switch off the inverter.
All our inverters are equipped with arc detection and all our materials are tested for fire safety in the event of an arc.
ServiceWe understand that, in addition to the purchase of a BiTile solar roof, you also want to be sure of its performance and safety. To this end, we are happy to provide support for the monitoring, maintenance and control of your PV installation. During the delivery, we provide a check with specific measurement and analysis equipment to exclude risks in the power circuit. It is good to repeat this periodically. By minimising the resistance in the string, your yield and your safety are guaranteed.
In this video, we explain the fire safety of rooftop systems and the tests we have carried out in this field.