Temperature-controlled cargo bodies use sandwich panels with a rigid insulating core bonded between two structural skins. The most common configurations combine a PP foam or PP honeycomb core with glass-fibre-reinforced thermoplastic skins, delivering the thermal resistance, structural strength, and low weight that refrigerated transport demands. The questions below unpack which panel types, core materials, and certification requirements matter most when specifying panels for cold chain applications.

This article covers the broader sandwich panel market. Compoform’s range is limited to PP honeycomb and PET foam cores for commercial vehicles and scaffolding.

Which panel types perform best in cold chain applications?

Fibre-reinforced thermoplastic sandwich panels with closed-cell foam cores perform best in cold chain cargo bodies. They combine continuous thermal resistance across the panel face, high stiffness-to-weight ratios, and resistance to moisture ingress, all properties that deteriorate quickly in alternative materials such as plywood or steel-framed constructions exposed to repeated wash-down cycles and temperature cycling.

The panel’s job in a refrigerated body is to do several things at once: resist the structural loads of cargo and road vibration, maintain a consistent thermal barrier, and survive years of condensation, cleaning chemicals, and temperature swings between ambient loading and sub-zero running temperatures. No single material layer achieves all of this, which is why the sandwich construction, with a lightweight insulating core and tough reinforced skins, has become the standard approach for reefer body builders across Europe.

For floor panels specifically, the panel must also handle forklift point loads and pallet jack wheels without deforming. This is where core density and skin ply count become the deciding variables, not just thermal performance.

What core materials are used in insulated cargo panels?

The core materials used in insulated cargo panels are closed-cell polymer foams and structural polymer honeycombs. Closed-cell PP foam cores are the most widely used in thermoplastic sandwich panels for refrigerated bodies because the closed-cell structure resists moisture absorption and provides measurable thermal resistance across a range of densities.

PP foam cores are available across a range of densities, from around 40 kg/m³ up to 140 kg/m³, and the density selected determines the balance between insulation performance, compressive strength, and panel weight. Lower-density foams offer better thermal resistance per unit weight but less resistance to point loads. Higher-density foams carry heavier loads but add weight to the structure.

PP honeycomb cores offer a different trade-off. The honeycomb geometry provides very high stiffness relative to weight, making it well suited to floor panels where structural performance under concentrated loads is the priority. The thermal resistance of a honeycomb core is lower than an equivalent-thickness foam core because the air columns in the honeycomb are not fully sealed in the same way as a closed-cell foam. For walls and roofs where thermal performance is the primary driver, foam cores are generally preferred. For floors where load-bearing is the primary driver, honeycomb cores are a strong choice.

It is worth noting that some panel suppliers use PU foam cores in refrigerated body applications. These offer high thermal resistance but are thermoset materials, meaning they cannot be recycled at end of life, a consideration that is increasingly relevant under EU ELV Directive obligations for commercial vehicle and trailer manufacturers.

What skin materials are used on refrigerated cargo panels?

Refrigerated cargo panels use glass-fibre-reinforced thermoplastic skins as the structural face layers. These skins bond to the core under heat and pressure, creating a monolithic panel that resists delamination even under repeated thermal cycling and mechanical stress. The skin surface finish is typically a white PET film for interior walls, or a textured anti-skid surface for floor panels.

The number of fibre plies in the skin determines its stiffness and impact resistance. A two-ply skin with fibres oriented at 0° and 90° suits wall panels where loads are distributed. A four-ply skin adds stiffness and impact resistance, making it appropriate for floors and areas exposed to forklift contact or cargo impact.

Glass fibre content in the skins typically runs at around 66 to 67% by weight, which gives the skin a high tensile modulus relative to its thickness. This is what allows a composite sandwich panel to span between frame members without deflecting under load, a property that steel or aluminium skins share, but at significantly greater weight.

For exterior surfaces on refrigerated bodies, UV resistance is a relevant factor. PET film surfaces tested to ISO 4892 maintain their appearance and surface integrity over years of outdoor exposure, which matters for body builders who want to avoid surface degradation that could compromise hygiene ratings or require repainting.

How does panel weight affect refrigerated vehicle payload?

Panel weight directly reduces the legal payload a refrigerated vehicle can carry. Every kilogram used in the body structure is a kilogram subtracted from the revenue-generating cargo capacity. For a full-size refrigerated trailer, switching from a steel-framed or plywood-lined body to a composite sandwich panel construction can recover meaningful payload, and that payload recovery compounds across every trip the vehicle makes.

The weight argument has a second dimension in 2026 that is increasingly standard in procurement conversations: electric vehicle range. Lighter body structures extend battery range in electric refrigerated trucks and vans. Every kilogram of structural dead weight reduces range per charge, which means weight reduction is a range argument as much as a payload argument. EV fleet buyers and fleet operators transitioning to electric refrigerated vehicles are asking about panel weight as a range specification, not just a payload specification.

A composite sandwich panel wall or floor panel is substantially lighter than a steel-faced equivalent of the same thickness. The structural skins carry the load, the core provides the insulation and shear resistance, and the result is a panel that replaces multiple material layers, insulation board, lining sheet, and structural frame, with a single component that does all three jobs at once. Fewer components also means faster body assembly, which reduces build cost for the body manufacturer.

What ATP certification requirements affect panel selection?

ATP certification, the Agreement on the International Carriage of Perishable Foodstuffs, sets minimum thermal performance requirements for refrigerated vehicles operating across international borders in Europe. The certification requires the body to achieve a specific K-coefficient (overall heat transfer coefficient), measured in W/m²K, which defines how well the body resists heat transfer between the interior and exterior environment.

Panel selection directly affects the K-coefficient. A thicker panel with a lower-conductivity core achieves a lower K-value, meaning better insulation. The ATP standard defines different classes of insulated body based on their K-coefficient, and the class required depends on the cargo type and the operating temperature range. Panels must be specified to achieve the required K-value across the full body assembly, walls, roof, floor, and doors, not just in isolation.

For body builders, this means panel thickness and core material cannot be selected on structural grounds alone. A panel that is structurally adequate but thermally insufficient will fail ATP testing. Conversely, over-specifying panel thickness to achieve a lower K-value than required adds unnecessary weight. The correct approach is to calculate the required K-coefficient for the intended ATP class, then select the minimum panel thickness and core density that achieves it, while still meeting the structural load requirements for the floor and wall panels.

ATP certification also requires periodic retesting of the body, which means the panel construction must maintain its thermal performance over years of service. Panels that absorb moisture, whether through damaged skins or permeable core materials, will see their thermal resistance degrade over time, potentially causing the vehicle to fail recertification. Closed-cell core materials and well-sealed panel edges are important for maintaining ATP compliance across the vehicle’s service life.

What’s the difference between GRP and thermoplastic composite panels for reefer bodies?

GRP (glass-reinforced polyester) panels use a thermoset resin system, while thermoplastic composite panels use a polymer matrix, typically polypropylene, that can be remelted and reformed. The practical differences for refrigerated body builders come down to recyclability, impact behaviour, repairability, and long-term regulatory compliance.

GRP panels are well established in the reefer body market and offer good stiffness and weather resistance. However, because the polyester resin is thermoset, GRP panels cannot be recycled at end of vehicle life. Under the EU ELV Directive, vehicle manufacturers face increasing pressure to demonstrate recyclability of body components. This is shifting procurement decisions toward thermoplastic composite panels, which are fully recyclable and align with CSRD sustainability reporting requirements that many European OEMs now need to meet.

Thermoplastic composite panels also behave differently under impact. Rather than cracking or shattering like a thermoset laminate, thermoplastic skins tend to deform and absorb energy, a property that reduces the risk of structural damage from minor impacts during loading operations. In a refrigerated body that is loaded and unloaded multiple times per day, this difference in impact behaviour has practical consequences for maintenance costs over the vehicle’s life.

From a production standpoint, thermoplastic panels can be thermoformed and welded, which opens fabrication options that are not available with GRP. Body builders can use heat to form curved sections or weld panel edges, rather than relying entirely on mechanical fasteners or adhesive bonding.

How Compoform Helps with Sandwich Panels for Temperature-Controlled Cargo Bodies

We design and manufacture fully custom thermoplastic sandwich panels for truck body builders and trailer manufacturers building refrigerated and temperature-controlled cargo bodies. Every panel we produce is made to order, you specify the core thickness, core density, skin ply count, and surface finish, and we manufacture to those requirements on our 72-metre double belt press production line in the Netherlands.

For refrigerated body applications, we work with you to match panel configuration to your ATP certification target, your structural load requirements, and your assembly process, not just to a standard datasheet. Panels are available in dimensions up to 13,500 mm × 2,950 mm, which means fewer joints in the body shell and simpler assembly for large trailer builds.

Here is what that looks like in practice:

• Wall panels: PP foam core with cross-ply or 2-ply glass-fibre skins and white PET film surface — optimised for thermal resistance and interior hygiene.
• Floor panels: PP honeycomb core with 4-ply anti-skid skins — self-supporting under forklift loads, with no aluminium subframe required. Removing the subframe eliminates a production step and reduces body weight.
• Custom dimensions: Panels cut to your exact specification, delivered on customised pallets ready for your production line.
• Edge protection: Edge sealing and edge bending protect the core from moisture ingress — important for panels that will be washed down regularly in a refrigerated body environment.
• Longevity: Thermoplastic composite floors last significantly longer than plywood in heavy transport use. Over a 15-year vehicle life, eliminating two or three plywood replacement cycles — including panel cost, installation labour, and vehicle downtime — makes the composite the lower-cost option per year of service, even at a higher unit price.

Before production, we review your body design, flag any configuration issues, and confirm the panel specification suits your assembly method and end-use requirements. We are an application partner through the build process, not a supplier that ships panels to spec and steps back. Talk to our engineering team about your refrigerated body project and we will work through the panel specification with you.

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