Composite insulated panels are used across thousands of UK industrial buildings. Of all the variables in their construction, the core material is the one that matters most - it determines fire behaviour, insurance conditions and the cost of compliance.
Back to Knowledge BaseComposite insulated panels – also called sandwich panels, or simply “whitewall” in the food industry – consist of two metal facings bonded to a central insulating core. They are manufactured in a factory under controlled conditions, which gives them consistent dimensions and performance characteristics that site-assembled cladding systems cannot match.
The outer skins are most commonly steel, though aluminium, stainless steel and GRP facings are also used in specific applications. The surface finish of the outer skin varies – foodsafe hygienic finishes for internal food production use, weatherproof coated finishes for external applications. These surface variations have no bearing on fire performance.
Composite panels are widely used in UK factories, cold stores, pharmaceutical facilities, distribution centres and food production buildings for walls, roofs and internal partitions. Thousands of UK buildings contain them – many with no accurate record of what type they are.
Of all the variables in composite panel construction, the core material is the one that matters most for fire risk and insurance purposes. This point cannot be overstated: two panels that look identical on the outside may have entirely different fire properties, insurance implications and regulatory compliance status depending solely on what is inside them.
The most common core materials in the UK building stock are Polyurethane (PUR), Polyisocyanurate (PIR), Expanded Polystyrene (EPS), Extruded Polystyrene (XPS), Mineral Wool and Phenolic Foam. PUR and early-generation PIR are organic foams that are combustible, produce toxic smoke when they burn, and in some formulations generate molten flaming droplets that spread fire. EPS and XPS behave similarly. More modern LPS-approved PIR has significantly better fire performance. Mineral wool is non-combustible and provides the best fire resistance. Phenolic foam sits between the two in terms of performance.
The core may be a block material bonded to the outer skins with adhesive, or it may be injected as a liquid and bond naturally to the skins as it expands and cures. Continuous injection panels – the dominant manufacturing method since the 1980s – generally have more consistent core properties than older bonded-block systems, but age, moisture ingress and installation quality all affect actual performance.
The practical challenge that makes composite panel assessment necessary is that core type cannot be established from visual inspection alone. Panel profile, fixing pattern, surface finish and colour give no reliable indication of what is inside. Manufacturer markings, where present, can narrow the field significantly – but records are often incomplete, panels have been over-clad, or the markings have simply worn away over time.
Core sampling and laboratory testing is the only method that provides certainty. Panel Check’s identification methodology combines desktop research, manufacturer knowledge, visual profiling and – where required – controlled intrusive investigation and laboratory analysis.
Food production environments place specific demands on composite panels that affect both the appropriate specification and the assessment methodology.
Hygienic surface requirements mean that most food production panels have smooth internal faces with specific surface coatings designed to withstand food-safe cleaning regimes – including regular high-pressure hot water washing and chemical sanitisers. These cleaning regimes can, over time, degrade joint sealants and create entry points for moisture. A Panel Check condition assessment specifically looks for evidence of cleaning-related deterioration and its impact on panel performance and joint integrity.
Walk-on ceiling panels are common in food production facilities, used to create maintenance access above production areas. These panels are subject to foot traffic loads, and the condition of the panel faces and the joints around access hatches is critical both for structural integrity and for hygiene compliance. Panel Check has specific experience in assessing walk-on ceiling systems, including the panel construction, support structure, access provisions and condition.
Temperature-controlled environments within food factories – chilled stores, blast freezers, cooling tunnels – use panels with higher insulation values than ambient-temperature areas, and those panels are subject to additional stresses from thermal cycling. The junction between temperature-controlled areas and ambient areas is a particular focus of Panel Check assessments, as this is where moisture movement and condensation-related deterioration most commonly occur.
The interaction between composite panel specification and food hygiene regulation is an area where Panel Check’s knowledge of both panel technology and food industry operating requirements provides particular value to food production clients.
If you need to definitively identify unknown foam or fibre core materials in your facility, view our accredited insulated panel core testing service.