New evidence for specifying insulation in flat roof assemblies beneath rooftop PV

New comparative testing carried out by the Fire Protection Association (FPA) is providing fire safety professionals with rare end-use evidence of how insulation behaves beneath rooftop PV, rather than relying on assumptions drawn from product-level classification. The results clearly demonstrate the crucial importance of assessing whole roof assemblies using evidence against assumed performance.

The tests carried out at the FPA research facility in Gloucestershire investigated how two different fire rated roof insulation products behave when a fire occurs under a PV array, mounted above a flat roof with reinforced bituminous membranes. The objective was to provide technical evidence of fire development on and within the roof assembly when exposed to a PV fire.

While significant fire spread was observed across the bituminous cap sheet and PV modules in both scenarios, the results showed that:

• There was no fire penetration through the full depth of the insulation layer in either roof build-up
• The air and vapour control layer (AVCL) remained intact in both tests
• Fire behaviour on the roof surface was broadly similar for PIR and stone wool insulated assemblies

The FPA report, released in full earlier this year, includes detailed test methology, instrumentation, implementation, observations and results.

Commenting on the report, Simon Storer, Chief Executive of Insulation Manufacturers Association, said: “With PV installations becoming an increasingly widespread feature of flat roofs, the industry needs evidence to underpin fire safety decisions. The FPA report provides this and reinforces the importance of assessing fire performance at a system level.”

For fire safety professionals, the findings underline why product-level classification cannot be relied on in isolation when assessing risk beneath a PV array. Roof mounted PV systems are increasingly common in the UK, and research of this type provides valuable insight into the fire performance of complete roof assemblies under defined conditions. IMA encourages fire safety practitioners to review the full report to support risk-based decision-making.

To download a summary of the testing, which includes links to the full report, click here

For more information about IMA visit www.insulationmanufacturers.org.uk