How BS EN 15725 2023 has changed fire classification for in-roof solar

Fire performance is a critical consideration in all building projects. As part of the Independent Review of Building Regulations and Fire Safety (also known as the Grenfell Tower Hackitt Report), there have been many changes in how products, systems and installations are classified in terms of fire safety. These sweeping changes have affected almost every aspect of the construction industry, including the specification and installation of solar panels.

While the intent behind these changes has been to strengthen fire safety, they have also created some unintended consequences. In this blog, we will discuss BS EN 15725:2023, the recent changes to the standard, and what they mean for solar panel specification and installation.

What is BS EN 15725:2023, and why does it matter for solar?

BS EN 15725:2023, previously BS EN 15725:2010, is titled ‘Extended application on the fire performance of construction products and building elements: Principle of EXAP standards and EXAP reports’. It sets out the rules for how fire test results can be extended to cover variations of certain construction products without needing to test every single version. This process is known as extended application (EXAP).

Stuart Nicholson, managing director at Marley, explains why, until recently, EXAP was useful for solar panel specification: “When it comes to solar PV systems, fire tests have traditionally been carried out on specific combinations of products, such as a roof-integrated mounting kit with a particular solar panel, or ‘module’. But, since testing every combination would be complicated and expensive, EXAP allowed test results to be extended to apply to variations that didn’t exactly match the test specimen. For example, there could be variations in size, configuration, wattage or roofing materials.”

However, Stuart warns that this is no longer the case: “With the changes to fire regulations, EXAP no longer applies to solar panels.”

The changes to BS EN 15725:2023

Previously, laboratories could use expert opinion as part of the EXAP process to confirm how products would perform beyond the scope of their initial tests. This approach is no longer permitted.

For most construction products, this isn’t an issue, as they fall directly under the Construction Products Regulations (CPR). However, solar PV modules are not explicitly covered – because they are considered electrical devices rather than construction products. This has created a regulatory gap, meaning many new modules are not undergoing fire testing. The only way to achieve a valid fire classification is through full system testing — an expensive and complex option that is not feasible for many manufacturers.

Some manufacturers, such as Marley, have conducted this testing, but many newer, higher-powered panels on the market have not been tested with their mounting kits. Stuart notes: “This is a much bigger issue now as a lot of panels have increased in wattage. Many of the new 400+W panels have not been tested with the mounting kits and therefore shouldn’t be used together.” As a result, specifiers are often uncertain about whether the products they are considering can demonstrate compliance.

Stuart adds: “The number of compliant systems on the market is actually diminishing as new technologies are released and older models are removed, but compliance testing is not being carried out on the new systems.”

How are solar panels tested for fire performance?

BS EN 13501 is the European fire classification standard for construction products and building elements. It is a family of standards that provides a framework for expressing fire performance based on results from specific test methods.

For solar panels, the relevant document is BS EN 13501-5:2016, Fire performance of roofs and roof coverings. Testing is carried out in combination with CEN/TS 1187:2012, Test methods for external fire exposure to roofs.

After testing to CEN/TS 1187, the results are classified using BS EN 13501-5 into categories such as BRoof(t1), BRoof(t2), BRoof(t3) and BRoof(t4), with t4 being the most demanding classification.

Stuart explains how Marley’s products have been tested: “Marley SolarTile® panels hold full BRoof(t4) certification. They are tested in combination with our mounting kits to ensure full compatibility and are designed to work seamlessly with the rest of the Marley roofing system. Because we have all the necessary certifications in place, we can give clients, installers and homeowners complete peace of mind.”

Solar panel certification schemes and fire performance

For specifiers seeking to minimise the complexity and uncertainty associated with selecting compliant solar panels, the Microgeneration Certification Scheme (MCS) and Flexi-Orb may offer guidance and reassurance.

• The MCS is a government-backed quality assurance scheme that certifies small-scale renewable energy products and the companies that install them. Compliance isn’t mandatory, but it is required to access certain financial incentives, such as government funding schemes or export tariffs. Under MCS, solar panels are certified to MCS 005 (Solar PV Standard) and mounting kits to MCS 012 (Pitched Roof Mounting Kits). However, having MCS certification doesn’t guarantee that a panel and mounting kit can be used together. They must also have been tested as a combination, and the specific panels must be listed on the MCS 012 certificate to ensure compliance and fire safety.
• Flexi-Orb is a UKAS-accredited certification scheme that focuses on the competence of installers for solar PV, electrical energy storage systems and EV charging points. While MCS certifies the product, Flexi-Orb certifies the installation. This gives specifiers confidence that the system has been installed safely and to recognised standards, helping to reduce risk around fire performance and regulatory compliance.

How specifiers can ensure compliance with fire performance standards

While demonstrating compliance has become more difficult, it remains essential. Using untested combinations can introduce safety risks and may affect insurance or warranty coverage, such as NHBC or LABC warranties. It could also render a system ineligible for financial incentives, including government grants or Smart Export Guarantee (SEG) payments.

Specifiers can help ensure compliance by:

• Ensuring that the specific solar panel and mounting kit combination has a verified fire classification, and that the panel model is listed on the MCS 012 certificate.
• Opting for proprietary systems that combine a dedicated solar panel and mounting kit, such as Marley SolarTile®.
• Working with experienced, certified installers (MCS or Flexi-Orb) who are familiar with current fire standards and installation requirements.
• Requesting documentation of testing and certification for the complete system.

Discuss fire performance and compliance with the experts at Marley

Here at Marley, our team of experts is available to provide advice and guidance on all matters of compliance – from solar panel specification and fire performance to wind resistance, ventilation requirements, dry-fix roofing and roof tile selection.

For detailed information about our SolarTile range of roof-integrated solar panels, visit our Marley SolarTile® page, or enquire about using the Marley complete Roof System on your next project.