Fire Resilience
Standards & Regulations

What to consider when installing solar panels on flat roofs

Lisa Stephens - Product Manager, Building Envelope
Lisa Stephens - Product Manager, Building Envelope
April 4, 2024

Flat roofs are not a new construction feature but they have evolved rapidly and are now designed to be fully functional spaces on many buildings. Today, flat roofs commonly house not just plant and building services equipment but energy efficiency infrastructure, social spaces, and much more. 

Are flat roofs suited for solar energy installations?

Using the roof for renewable energy generation is a great way to make efficient and practical use of the space. Factors like the cost of living crisis, increasing energy prices globally and the drive towards net zero contribute to the growing number of solar installations.

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 EU1. In the coming years, the EU is even proposing to make solar panel installations mandatory on certain types of buildings.

Do solar panels increase the fire risk on the roof?

It is the responsibility of all building stakeholders (designers, specifiers, owners, contractors and insurers) to take into account the impact that future changes to the roof may have on the fire safety strategy for the building.

A fault tree analysis by the University of Edinburgh2 concluded that “Rooftop PV systems are promising electrical power sources and a potential fire risk at the same time. In the qualitative fault tree analysis, seven major events were defined as the potential ignition sources leading to the major event, a PV-related fire. Herein, it was found that arcing is the major contributor of fire events, which arise from poor-quality products, planning and installation errors, component damages during transportation, operation errors, lack of regular inspection and maintenance, as well as weathering effects.”

The BRE stated in a report3 that arcing can create temperatures that are “easily hot enough to melt glass, copper and aluminium, and to initiate the combustion of surrounding materials”.

Are there risks for the rest of the building?

An important consideration is how the rooftop installation is integrated with the internal building infrastructure. Fixings and building services connections like cabling can have an impact on minimum periods of fire resistance and/or compartmentation and need to be part of the risk profile.

A developed fire below the roof could spread to the roof, through unprotected PV cable penetrations, which has the potential to create a more severe fire and wider-reaching damage to the property.

What about regulation for rooftop solar installations?

Threat of fire from above the roof is considered in classifications such as BROOF(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. 

Designers should always be vigilant in regard to all potential fire risks and find a solution that has passed fire resistance tests and can prove its fire resistance (REI) rating. 

Where can you find more information about fire safety in flat roofs?

ROCKWOOL has published a whitepaper ‘Flat roofs: The functional fifth façade’ which explores the fire safety implications of modern multifunctional roofs and discusses best practices for identifying and mitigating the risks. It also explains the role of the guidance provided in approved documents, including Approved Document B (ADB) for fire safety, and examines potential limitations of such advice for non-standard flat roof circumstances and scenarios. 

Download the whitepaper now. 

Functional Fifth Facade CPD Web Listing Image
CPD: The Functional Fifth Facade

Understand the role of the modern flat roof, and how to identify and mitigate fire risks in this new CPD, ‘Flat roofs: The functional fifth façade’.

CPD: The Funcional Fifth Facade
CPD

References

  1. European Commission (May 2022): Communication on EU solar energy strategy  
  2. Nur Aliah Fatin Mohd Nizam Ong, et al (April 2022): Fault tree analysis of fires on rooftops with photovoltaic systems  
  3. BRE (May 2018): Fire and Solar PV Systems – Investigations and Evidence  

Webpage history

Our experts continually review and update our articles when legislation changes or new information becomes available. 

First published: 04/04/2024

Product Management Headshot - Lisa Stephens

ROCKWOOL Group