Lisa Stephens, Product Manager for the Building Envelope at ROCKWOOL^® UK, explains which safety measures need to be considered before installing solar panels on a roof

As the result of increased efforts to reduce carbon emissions, coupled with the rising cost for energy and general living expenses, the UK and Europe have seen a rapid growth of the market for solar energy.

The European Commission reports that the cost of solar power has decreased by 82% over the last decade, making it the most competitive source of electricity in many parts of the EU.

As of the end of June 2023, there was a total of 15.2 GW solar capacity in the UK across 1,353,261 installations.

This represents an increase of 6.7% (952MW) since June 2022.

Solar Energy UK forecasts that the UK can achieve 40GW of solar capacity by 2030.

Flat roofs have been used as an additional space to house building services equipment, including installations for the generation of renewable energy, for many years.

When planning the installation of roof-top solar panels, all parties involved (designers, specifiers, owners, contractors and insurers) have to be aware of any associated potential fire risks, and engaged in mitigating them.

Building regulations and practical guidance

As the use of flat roofs evolve, and potential sources of ignition increase, consideration towards the way in which flat roof materials react to fire becomes increasingly more important.

It is the responsibility of those designing and carrying out building works to meet the statutory requirements of the Building Regulations.

Whilst the statutory guidance in Approved Document B (ADB) covers common building  applications, simply complying with the guidance in ADB does not provide a guarantee of compliance with Building Regulations as the Approved Document cannot cater for all circumstances, variations and building innovations.

Those with responsibility for meeting the requirements of building regulations will need to consider themselves as to whether or not the guidance is sufficient for ensuring fire safety in the particular circumstances of their case.

Among other complex applications, roof-top solar panel installations are currently not explicitly covered within the statutory guidance of ADB and therefore require more careful consideration towards fire safety.

For flat roofs, the requirements under the building regulations regarding the potential for fire spread are set out in Requirement B4: External Fire Spread:

1. The external walls of the building shall adequately resist the spread of fire over the walls and from one building to another, having regard to the height, use and position of the building.
2. The roof of the building shall adequately resist the spread of fire over the roof and from one building to another, having regard to the use and position of the building.

What needs to be considered for roof-top solar installations

While utilising roof space for practical purposes is more of a well-established concept, complex considerations still apply.

Statutory guidance for flat roof fire safety, including ADB, sets out key provisions for some of the practical applications indicating routes to compliance for the building regulations.

These include plant rooms, rooflights and junctions with compartment walls.

There is also guidance in BS 8579:2020 ‘Guide to the design of balconies and terraces’, which discusses the fire performance required by balconies and terraces, and references plant equipment and compartmentation.

However, across these documents there is no specific guidance for the use of solar panels on flat roofs – a practical use that is increasingly common as specifiers incorporate the solution to address energy efficiency and sustainability benefits.

Research and real-world evidence point to solar solutions introducing additional fire risk to flat roofs.

There are known incidences of solar panel ‘arcing’ in which electrical energy passes through air gaps and can cause ignition of nearby materials, or the solar panel itself, due to the high temperatures involved (described as “easily hot enough to melt glass, copper and aluminium, and to initiate the combustion of surrounding materials”).

Solar panels can also complicate matters for fire and rescue services.

The Institute of Fire Engineers has noted that so long as a panel is exposed to light (even artificial light), “parts of the system are always live”, even if the building has otherwise been isolated from electricity.

Therefore, there are electrical considerations during the control and submission of a fire.

Moreover, solar cells within panels can emit toxic and dangerous fumes when burning.

Compliance and liability

In England, ADB provides guidance on how designers can meet building regulation requirements for fire safety – but there are multiple routes to compliance, and different ways to demonstrate an appropriate level of fire protection.

Supplements cover the requirements for specific applications.

For some sectors, specialist guidance such as HTM 05-02 (Health Technical Memorandum) or BB100 (Fire safety design for schools), can also influence decision-making.

Responsible parties must consider carefully whether their specific project adheres to the statutory requirements, rather than to the guidance alone.

In relation to roofs and façades, designers should be vigilant in regard to all potential fire risks.

Threat of fire from above the roof is considered in classifications such as B_ROOF(t4) (BS EN 13501-5), but exposure to fire from below the roof may not always be adequately addressed.

The absence of fire stopping seals to building services and penetrations that pass through the roof may create paths for fire to spread to the roof, from below.

Against a complex legislative backdrop, one simple way to mitigate risk is to select non-combustible materials throughout the fifth façade.

The trend towards increasingly multifunctional roofs only strengthens this case.

ROCKWOOL recently launched the new whitepaper ‘Flat roofs: The functional fifth façade’ will help those involved in the design and installation of flat roofs to make responsible choices when selecting materials to enable a modern flat roof to be multifunctional, safe and long-lasting.

It offers practical advice to simplify specification whilst going above and beyond legislative requirements.

For more information and to download the whitepaper go to: https://rockwool.link/ffpr-ifsj

This article was originally published in the March 2024 issue of International Fire & Safety Journal. To read your FREE digital copy, click here.