Combination of PIR and solar panels

Fire safety is an important issue for building owners and users, but also for insurance companies. Fire is a significant factor in determining insurance risk. If the risk of fire is high, this means that there is a greater chance of damage being caused by fire, which for the insurer means that there is a greater chance of having to pay out on claims. To compensate for this risk, the insurer will usually increase the premium. Other factors also play a role in determining the premium, such as the value of the object to be insured, the location and the type of construction.

It is important to understand that insurers calculate premiums based on the likelihood of damage, rather than on the specific circumstances of an individual customer. In recent years, a great deal of attention has been paid to the risk of fire on flat roofs with solar panels (PV systems).

Problems caused by installation errors

Research has shown that fires are mainly caused by installation errors and the use of substandard materials in PV systems, including the associated cabling and peripheral equipment (such as connectors). Agreements have now been made in this area for standards and inspections.

Insurance companies and some regulators are now questioning whether the usual level of fire safety is adequate for flat roofs with PV systems on them. In addition to the risk of a fire starting in the PV system, they are also concerned that PV panels could intensify a fire as a result of radiation.

Comparative test between mineral wool and PIR under a PV system

As a simple 'solution', a number of insurance companies have proposed simply allowing only 'non-combustible insulation' in the construction of roofs with PV systems. Mineral wool is often considered for this purpose. However, the fact is that PIR is used for many flat roofs in practice. In addition to its excellent thermal performance, PIR has outstanding compressive strength, which makes the insulation material particularly suitable for the installation of PV systems.

In order to verify whether the proposed requirement is justified, PU Europe commissioned a comparative test. Two roof systems approved by the renowned American testing institute FM APPROVAL were selected for this purpose: one insulated with PIR and one with MW. The PV panels were installed in a configuration that is commonly used, and a gas burner was used as an external ignition source.

Conclusion: no difference

In both tests, the spread rate of the flame front under the PV modules and across the roof was comparable. No major differences were found apart from the PV panels. No major differences were found between the insulation layers apart from the PV panels in terms of fire spread across the roof systems.

Just over 25% of the thickness of the PIR insulation was charred, and the temperature in and on the roof cooled continuously after the PV panels had stopped burning. The damage to the underlying structure was even slightly less with PIR than with mineral wool.