Metal Panel Insulation Thickness Chart

A refrigerated truck OEM in southern Germany rejected 320 panels last March. Thickness variance hit 1.2mm across a batch spec’d at ±0.5mm tolerance. Metal panel insulation failures at that scale don’t just create scrap — they stop assembly lines, blow delivery schedules, and cost fleet contracts. The panels wouldn’t seat in the fixture. The GRP facing cracked under the press. Six weeks of production lost while a replacement batch shipped from the other side of the world. That OEM now requires thickness certification with every pallet. You probably should too.

We built this reference from 15 years of production data across PU, XPS, PET, and mineral wool cores. Thickness mapped to R-value per inch. Weight per square foot broken down by gauge, facing material, and core density. Side-by-side numbers — a 4-inch PU panel delivers R-24 versus EPS at R-14.4, a 66% thermal gap that most catalogs never publish because the supplier only manufactures one core. Our line runs all four. You get the full comparison in one chart instead of stitching data from three sources and hoping the test conditions match.

Metal Panel Insulation Thickness at a Glance

Insulated metal panel thickness spans 1.5″–8″ (38mm–203mm), but core material selection shifts total R-value by up to 80% at identical thickness. Below are the numbers our engineers reference daily.

Thickness, R-Value, and Weight Benchmarks by Core Material

We compiled these benchmarks from our own production data combined with published industry specifications. All R-values are per inch of core thickness; weight figures reference 26/26 gauge steel facings unless noted. Use these as your baseline when modeling BOM weight and thermal performance for vehicle or cold storage assemblies.

• PU (Polyurethane) Foam Core — R-6.0 to R-6.5 per inch: Highest thermal resistance among foam options. At 4″ thickness, delivers approximately R-24 to R-26 total. Weight: ~2.62 psf (26/26 gauge steel facings). This is our most requested core for refrigerated truck bodies and RV wall assemblies where minimizing thickness while maximizing insulation is critical.
• XPS (Extruded Polystyrene) Foam Core — R-5.0 per inch: Strong moisture resistance makes it suitable for marine and high-humidity environments. At 4″ thickness, delivers R-20 total. Roughly 10–15% lighter per cubic foot than PU at comparable densities.
• PET (Polyethylene Terephthalate) Foam Core — R-4.0 per inch: Recyclable thermoplastic core with consistent density. At 4″ thickness, delivers R-16 total. Often selected where sustainability reporting requirements demand documented recycled content.
• Mineral Wool (Rockwool) Core — R-3.0 to R-3.3 per inch: The trade-off is clear: lower R-value per inch, but Class A fire rating (ASTM E84). At 4″ thickness with 26/26 gauge facings, weight jumps to ~4.43 psf — a 69% penalty over foam cores. Specified for fire-rated partitions and industrial facilities where code compliance overrides weight concerns.

Gauge and Facing Impact on Panel Weight

Gauge selection directly affects your per-square-foot weight budget. At 4″ panel thickness, upgrading from 26/26 to 22/22 gauge steel increases weight from approximately 2.62 psf to 3.63 psf — a 38% increase with zero change in thermal performance. For specialized vehicle manufacturers working within homologation weight limits, this trade-off is non-trivial.

Our GRP/FRP and CFRT facing options reduce facing weight by 30–40% compared to equivalent steel gauges while maintaining structural stiffness. On a 500 sqft RV wall build, switching from 26-gauge steel to GRP facings can save over 60 lbs of total vehicle weight without sacrificing insulation value.

Production Tolerances and Consistency

Our production line maintains ±0.5mm thickness tolerance across all custom panel runs from 10mm to 200mm core thickness. Continuous thickness monitoring on the line ensures each panel meets dimensional specs before shipment — because for vehicle engineers, thickness inconsistency creates assembly rejects, and rejected panels kill production schedules.

Daily output exceeds 1,700 square meters, meaning even large-volume orders for truck body fleets or modular housing projects ship on predictable timelines. Panels are available in standard widths up to 42″ (1,067mm), with custom widths configured to your CAD drawings.

Insulated Metal Panel Thickness Chart

Insulated metal panels range from 1.5″ to 8″ (38mm–203mm) in thickness, but vehicle engineers rarely need beyond 6″ — the critical decision is matching gauge, core material, and thickness to hit both weight budgets and thermal targets simultaneously.

Standard Gauge and Thickness Combinations

Most insulated metal panel manufacturers offer facings in 29, 26, 24, and 22 gauge steel. Our production line at Rax Panel runs panels from 10mm to 200mm total thickness with continuous thickness monitoring holding tolerance to ±0.5mm. For vehicle applications — RV walls, refrigerated truck bodies, marine bulkheads — the industry sweet spot sits between 2″ and 4″ (50mm–100mm). Going thicker adds insulation value but eats into payload capacity fast.

The gauge-to-weight relationship is linear but punishing at scale. A 4″ wall panel with 26/26 gauge facings weighs approximately 2.62 psf (12.8 kg/m²). Step up to 22/22 gauge and you jump to 3.63 psf (17.7 kg/m²) — a 38% weight increase just from heavier steel skins. Across a 500 sqft RV wall, that is 505 extra pounds of dead weight affecting fuel efficiency and potentially pushing the vehicle over homologation limits.

This is precisely where composite facings change the equation. Our GRP/FRP and CFRT facing options deliver 30–40% weight reduction compared to equivalent steel skins while maintaining structural flatness and impact resistance. For a 4″ panel, switching from 26-gauge steel to GRP facings can drop panel weight below 2.0 psf — a meaningful savings when every kilogram counts toward vehicle compliance.

• Standard thickness range: 1.5″–8″ (38mm–203mm), with 2″–6″ covering 90% of commercial applications
• Gauge options: 29ga (0.014″), 26ga (0.018″), 24ga (0.024″), 22ga (0.030″)
• Weight span: 2.05 psf (1.5″, 26/26) to 8.26 psf (8″, 22/22 heavy profile)
• Standard maximum width: 42″ (1067mm) for most profiles
• Production tolerance: ±0.5mm thickness maintained through continuous line monitoring

Core Material R-Value Per Inch

Not all foam cores insulate equally. PU foam delivers R-6.0 to R-6.5 per inch at 2.0 pcf core density — roughly 80% higher thermal resistance than EPS at R-3.6 per inch. For a 4″ thick panel, that means PU achieves R-24 versus R-14.4 for EPS. If your refrigerated truck must maintain -20°C in a 35°C ambient environment, that difference determines whether your compressor cycles constantly or holds steady.

XPS sits between PU and PET at approximately R-5.0 per inch. PET foam delivers R-4.0 per inch but offers better dimensional stability at elevated temperatures and is fully recyclable — a growing requirement for European vehicle OEMs tracking lifecycle environmental impact.

Mineral wool (rockwool) presents a tradeoff engineers must calculate carefully. At R-3.0 per inch, its thermal performance sits well below PU — but it achieves Class A fire rating without additional retardants. The weight penalty is severe: a 4″ mineral wool panel with 26/26 facings weighs 4.43 psf versus 2.62 psf for foam core. That is a 69% weight increase. For fixed-structure cold storage where weight is irrelevant, mineral wool makes sense. For vehicles, it rarely does unless fire codes absolutely demand it.

• PU/PUR foam: R-6.0 to R-6.5 per inch — highest thermal resistance, standard for refrigerated transport
• PIR foam: R-5.5 to R-6.0 per inch — improved fire performance over PU, marginally lower R-value
• XPS foam: R-5.0 per inch — good moisture resistance, suitable for high-humidity environments
• PET foam: R-4.0 per inch — recyclable, dimensionally stable, increasingly specified for European compliance
• Mineral wool: R-3.0 per inch — Class A fire rating, 69% heavier than foam at equivalent thickness
• PP Honeycomb: R-value varies with cell size — primarily chosen for structural stiffness, not thermal performance

We manufacture panels using all of these core materials at Rax Panel, and we run experimental testing for each customer project to validate that the finished panel meets the exact data standards their application demands. The right choice is never simply “highest R-value” — it is the intersection of thermal target, weight budget, fire code, and cost ceiling for the specific vehicle or structure you are building.

Weight vs. Thickness Tradeoffs

Upgrading from 26-gauge to 22-gauge steel facings adds roughly 38% panel weight with zero thermal gain. For vehicle builds, switching to GRP/FRP or CFRT composite facings cuts facing weight by 30–40% while maintaining structural rigidity.

Gauge Impact on Total Weight

Gauge selection is purely a structural and durability decision — it has no effect on R-value. At 4″ thickness with a PU foam core (R-24.0 total), the thermal performance is identical whether you specify 26-gauge or 22-gauge steel facings. What changes is the load on your vehicle frame. Our production data aligns with published industry weights: a 26/26 gauge wall panel at 4″ and 42″ width runs approximately 2.62 psf (12.8 kg/m²). Stepping up to 22/22 gauge pushes that figure to 3.63 psf (17.7 kg/m²). On a 500 sqft truck body, that gauge upgrade alone adds over 500 lbs (227 kg) — mass that eats directly into payload capacity.

For engineers working within strict vehicle homologation limits, the intermediate gauge options deserve attention. Here is how the weight scales at a fixed 4″ thickness with PU foam core at 42″ panel width:

• 26/26 gauge (0.55mm/0.55mm): ~2.62 psf — lightest standard steel option; suitable for dry freight and RV applications where impact resistance is moderate.
• 24/24 gauge (0.63mm/0.63mm): ~3.10 psf — a marginal weight penalty of roughly 18% over 26/26, with measurably better dent resistance for high-traffic loading areas.
• 22/22 gauge (0.76mm/0.76mm): ~3.63 psf — maximum steel durability; carries a 38% weight penalty over 26/26 with no improvement in insulation value.
• Mineral wool core, 26/26 gauge, 4″: ~4.43 psf — a 69% weight penalty compared to PU foam at the same gauge and thickness, justified only when Class A fire rating is non-negotiable.

The core material choice compounds the weight equation further. PU foam delivers R-6.0 to R-6.5 per inch at roughly 2.0 pcf core density. Mineral wool achieves only R-3.0 per inch but at significantly higher density. If your spec requires a fire-rated assembly, you are forced into that weight penalty — there is no engineering shortcut around it. For everything else, foam cores (PU, XPS at R-5.0/inch, PET at R-4.0/inch) keep the panel mass competitive.

Lightweight Alternatives for Vehicle Builds

Steel facings are the default in commercial construction, but vehicle manufacturers operate under a fundamentally different constraint: every kilogram saved on the body structure translates directly to payload or fuel efficiency. This is where composite facings change the calculation. Rax Panel’s GRP/FRP and CFRT facing options reduce facing weight by 30–40% compared to equivalent-gauge steel while delivering comparable flexural stiffness — a capability that standard insulated metal panel catalogs rarely address.

For specialized vehicle applications, we regularly engineer panels with the following facing and core combinations:

• GRP/FRP facing + PU foam core: Maximum thermal performance (R-6.0–6.5/inch) with the lightest facing option. Ideal for refrigerated truck bodies and RV walls where every pound matters.
• CFRT facing + XPS core: Continuous fiberglass reinforced thermoplastic facings are lighter, thinner, and more resilient than traditional GRP. Paired with XPS (R-5.0/inch), this configuration suits marine and vessel interiors where moisture resistance is critical.
• GRP facing + PP honeycomb core: The lowest weight configuration available — honeycomb cores eliminate foam mass almost entirely. Best for non-thermal structural applications like furniture panels, flooring, and bulkheads.
• Aluminum facing + PET foam core: A middle-ground option offering aluminum’s workability with PET’s stable R-4.0/inch thermal performance. Common in mobile home and modular construction where cost and weight must balance.

Our engineers work from your BOM requirements — target weight per square meter, minimum R-value, and structural load cases — to select the optimal core and facing combination. Thickness tolerances are held to ±0.5mm across our continuous production line, which outputs over 1,700 sqm daily. For a vehicle engineer specifying 500 sqft of wall panel, switching from 26-gauge steel to GRP facings on a 4″ PU core can drop total wall weight by approximately 25–30% without sacrificing thermal performance. That is the margin between passing and failing a GVWR homologation check.

Choosing Thickness by Application

There is no universal “correct” panel thickness. The right spec is the intersection of target temperature delta, vehicle or structure weight budget, and fire code requirements — mapped to a specific core material.

Cold Room and Refrigerated Truck Panels

Cold storage and refrigerated transport demand the highest insulation performance per inch of any application we manufacture for. The reason is simple: every millimeter of unnecessary thickness eats into internal cargo volume, while every millimeter of shortfall causes compressor overwork and temperature drift. PU foam core at 2.0 pcf density delivers R-6.0 to R-6.5 per inch, making it the standard choice for these applications. Our production line maintains ±0.5mm thickness tolerance across runs exceeding 1,700 sqm daily, which is critical when you are assembling CKD refrigerated truck kits that must seal tightly on the first fit.

For refrigerated truck bodies, we typically specify panels in the 3″ to 6″ (76mm–152mm) range depending on the operating temperature zone. A truck maintaining 0°C to 5°C for fresh produce generally requires 3″ to 4″ PU core panels. Frozen cargo at -18°C to -20°C demands 5″ to 6″ thickness to maintain the thermal delta during long-haul routes and frequent door openings. Going below these specs to save on upfront material cost is a false economy — compressor energy consumption and temperature excursion losses will exceed the panel cost difference within the first 18 months of operation.

For static cold rooms and walk-in freezers, the calculations shift slightly because weight is no longer a constraint. Panels from 4″ to 8″ (102mm–203mm) are common. At 4″ thickness with 26/26 gauge steel facings, a PU core panel weighs approximately 2.62 psf and delivers roughly R-24 total thermal resistance. If fire rating is a requirement — for example, in food processing facilities subject to GMP audits — mineral wool core at the same 4″ thickness provides Class A fire performance but carries a 69% weight penalty at 4.43 psf with only R-12 thermal resistance. That tradeoff is why many of our customers use hybrid assemblies: mineral wool panels near heat sources and PU panels for the main enclosure.

• Fresh storage (0°C to 5°C): 3″–4″ PU core, R-18 to R-24
• Frozen storage (-18°C to -20°C): 5″–6″ PU core, R-30 to R-36
• Deep freeze (-25°C to -30°C): 6″–8″ PU core, R-36 to R-48
• Fire-rated cold room: 4″–6″ mineral wool core, Class A, R-12 to R-18

RV and Mobile Home Wall Panels

Recreational vehicles live and die by weight budgets. Saving 0.5 psf across 500 sqft of wall and roof surface translates to meaningful gains in fuel efficiency, payload capacity, and vehicle homologation compliance. This is where facing material selection matters as much as core thickness. A 2″ thick panel with 26/26 gauge steel facings weighs roughly 2.10 psf. Swap to GRP/FRP facings and that same 2″ panel drops to approximately 1.3 to 1.4 psf — a 30 to 40% weight reduction with comparable structural stiffness. For RV manufacturers, this is not a marginal improvement. It is often the difference between meeting and failing gross vehicle weight rating limits.

We manufacture RV wall panels from 1″ to 3″ (25mm–76mm) thickness depending on the insulation target and structural load. Most Class C and Class A motorhomes use 1.5″ to 2″ panels with XPS or PU core. XPS at R-5.0 per inch offers better moisture resistance than PU for roof applications where condensation is a persistent issue, while PU at R-6.0 to R-6.5 per inch is preferred for wall panels where maximum thermal performance in the thinnest profile is the priority. Travel trailers targeting three-season use often specify PET foam core at R-4.0 per inch as a cost-effective middle ground.

Our CFRT facing sheets — continuous fiberglass reinforced thermoplastic — are increasingly specified for RV interiors. They are lighter, thinner, and more resilient than traditional FRP sheets with gelcoat. Combined with a PP honeycomb core for furniture panels and interior partitions, this configuration delivers structural panels under 1.0 psf. Thickness tolerance is critical here: panels that deviate beyond ±0.5mm create gaps in assembly that rattle, leak, and generate warranty claims downstream.

• RV walls (temperate climate): 1.5″–2″ PU or XPS core with GRP facing
• RV walls (extreme climate): 2″–3″ PU core with GRP or aluminum facing
• RV roofing: 1.5″–2.5″ XPS core (superior moisture resistance)
• Mobile home partitions: 1″ PP honeycomb or PET foam core with CFRT facing
• RV flooring: 2″–3″ plywood-facing foam sandwich for load-bearing capacity

Warehouse and Modular Construction Panels

Modular construction and warehouse applications prioritize different variables than vehicle manufacturing. Weight is still relevant for crane lifting and transport logistics, but the dominant concerns shift to fire code compliance, long-term thermal efficiency over 20 to 30 year building lifespans, and structural span capability. Panel thickness in this sector ranges from 2″ to 6″ (51mm–152mm), with the specific spec driven by local energy codes and the occupancy classification of the structure.

For standard warehouse enclosures where climate control targets are moderate — maintaining 15°C to 25°C — a 2″ to 3″ PU core panel with steel or aluminum facings typically satisfies insulation requirements at R-12 to R-18. Modular building projects targeting stricter energy codes, particularly in Northern Europe and Canada, often require 4″ to 6″ panels to achieve the R-24 to R-36 values needed for wall assemblies. The cost premium from 3″ to 5″ is approximately 35 to 45% in material, but the operational energy savings over a 25-year building life generally justify the upfront investment in markets with heating-degree-day counts above 4,000.

Fire rating requirements are where core material selection becomes non-negotiable. Standard PU and PIR foam cores achieve Class B fire performance with fire retardant additives. For applications requiring Class A fire rating — warehouses storing flammable goods, multi-story modular buildings, or facilities subject to stricter insurance underwriting — mineral wool (rockwool) core panels are specified. The tradeoff is significant: at 4″ thickness, mineral wool panels weigh 4.43 psf versus 2.62 psf for PU foam in the same 26/26 gauge configuration. That 69% weight increase must be factored into structural steel design and lifting calculations during the engineering phase, not discovered on site during assembly.

We also manufacture PUR and PIR sandwich panels specifically for building envelope applications, along with rockwool panels for fire-rated assemblies and hollow plastic formwork panels for concrete modular construction. Each specification is engineered to the project’s local code requirements. Our engineering team conducts experimental testing to validate that the composite panel configuration meets the required data standards before production begins, which eliminates the compliance risk that procurement teams face when importing generic panels with uncertain fire and thermal certifications.

• Standard warehouse envelope: 2″–3″ PU or PIR core with steel facing, Class B fire rating
• Energy-efficient modular walls: 4″–6″ PU core, R-24 to R-36
• Fire-rated assemblies (Class A): 4″–6″ mineral wool core, steel or stainless steel facing
• Exterior wall cladding: 1.5″–3″ aluminum composite or compact laminate HPL panels
• Modular concrete formwork: Hollow plastic formwork panels, reusable 50+ cycles

Thickness Tolerances and Manufacturing Consistency

A thickness deviation of just 1mm can misalign assembly jigs and break seal joints. We maintain strict ±0.5mm composite sandwich panel thickness tolerances to prevent cascade failures on your production floor.

Why Thickness Variation Kills Assembly

Veteran engineers know that specifying panel materials for RVs, truck bodies, and marine vessels leaves zero room for dimensional error. When panel thickness drifts outside of tolerance, it immediately cascades into structural and operational failures downstream. A panel that is too thick will not fit into the designed aluminum extrusions or bonding jigs, forcing line workers to spend time grinding down the core. This destroys the thermal envelope and compromises the structural integrity of the facing.

Conversely, a panel that is too thin creates uneven gaps at the seal lines, inviting water intrusion and reducing the effectiveness of the insulation. In high-volume vehicle manufacturing, these inconsistencies force line stoppages and drive up labor costs dramatically.

• Jig Misalignment: Automated welding and bonding fixtures require precise dimensions. A cumulative +0.5mm error across a multi-panel run will jam the assembly fixture.
• Weight Homologation Failure: Over-specifying thickness to “be safe” adds unexpected weight. We specify exact facing gauges and core densities to ensure panels do not push the vehicle over its strict weight homologation limits.
• Thermal Bridging: Inconsistent thickness leaves uneven gaps at panel joints, degrading the overall R-value of the insulated enclosure and risking failure in cold-chain compliance.

This is why our engineering team strictly monitors our advanced continuous composite panel production line in real-time. With over 15 years of production experience and a daily output exceeding 1,700 square meters, our facility maintains a rigid ±0.5mm thickness tolerance. For specialized vehicle manufacturers, dimensional consistency is just as critical as the weight per square foot or the core material’s R-value.

See Our Industrial and Agricultural Insulated Metal Panel Systems.

Browse our full inventory of core panel systems built for heavy-duty agricultural and industrial buildings. You will find detailed configurations, dimensions, and application specs to match your exact structural requirements.

Explore Our Panel Range →

Gauge Decoded: Steel Thickness Explained

Selecting between 24-gauge and 26-gauge steel facings is a direct tradeoff between impact resistance and vehicle payload limits. Over-specifying gauge adds dead weight that destroys fuel efficiency.

24 Gauge vs. 26 Gauge: Cost and Durability

In the structural panel industry, the gauge system works in reverse: a lower gauge number indicates a thicker, heavier metal sheet. A standard 26-gauge steel facing measures approximately 0.0179 inches (0.45mm), while a 24-gauge facing is noticeably thicker at 0.0239 inches (0.61mm). For specialized vehicle engineers, this 0.006-inch variance dictates the structural durability of the final assembly and drastically shifts the vehicle’s center of gravity. We consistently advise engineers to calculate the exact abuse load the panel will take before defaulting to a heavier gauge out of habit.

To understand the payload impact, look at the hard data for a standard 4-inch (101.6mm) insulated wall panel:

• 26/26 Gauge: Weighs approximately 2.62 psf (12.8 kg/m²). This is the industry baseline for standard RV sidewalls and dry freight truck bodies where minimizing curb weight is the primary KPI.
• 24/24 Gauge: Weighs roughly 3.02 psf (14.7 kg/m²). Provides higher dent resistance for commercial wall applications but adds immediate weight penalties.
• 22/22 Gauge: Weighs approximately 3.63 psf (17.7 kg/m²). Upgrading from 26-gauge to 22-gauge steel increases the panel weight by nearly 38%, reserved strictly for high-impact industrial zones.

Specifying 24-gauge or 22-gauge metal drives up both your raw material costs and your shipping freight. More critically for vehicle homologation, adding unnecessary mass to the envelope limits your payload capacity. For a 500 sqft (46.4 m²) RV build, upgrading from 26-gauge to 22-gauge steel facings dumps an extra 500 lbs (226 kg) straight onto the chassis. If you are fighting to keep a vehicle under a specific GVWR, heavy gauge steel will break your budget fast.

We manufacture our GRP/FRP and CFRT sandwich panels specifically to eliminate this weight penalty. By utilizing fiberglass reinforced facings instead of 24-gauge steel, you secure the necessary structural rigidity and impact resistance while slashing the facing weight by 30% to 40%. Our continuous production line maintains a strict ±0.5mm thickness tolerance on these composite panels, ensuring you get the exact structural data your CAD models require without risking assembly rejects.

Three Types of Insulated Metal Panel Cores

At 4″ thickness, PU delivers R-24 versus EPS at R-14.4 — a 67% thermal advantage. Mineral wool adds Class A fire compliance but carries a 69% weight penalty over foam cores. Select your core based on the binding constraint: thermal performance, fire rating, or vehicle weight budget.

EPS (Expanded Polystyrene) Core Panels

EPS delivers an R-value of approximately 3.6 per inch at a core density around 1.0 to 1.5 pcf. It is the lowest-cost foam core option in our catalog, making it the default choice for dry freight truck bodies, standard wall cladding, and applications where thermal performance is secondary to budget. For manufacturers sourcing panels in bulk, EPS keeps the per-unit material cost down and simplifies logistics — the panels are lighter and easier to cut on-site.

The trade-off is clear: at 4″ thickness, EPS yields R-14.4 total thermal resistance. If your cold chain requires sustained temperatures below -10°C (14°F), EPS will not hold the envelope without significantly thicker profiles — which in turn pushes up freight costs and reduces internal cargo volume. EPS also carries a Class C fire rating, restricting its use in compartments where fire codes demand Class A or Class B compliance.

• R-Value per inch: ~3.6
• Typical density: 1.0–1.5 pcf (16–24 kg/m³)
• Fire rating: Class C
• Best fit: Dry freight bodies, standard partition walls, budget-sensitive modular builds

PU (Polyurethane) Foam Core Panels

PU foam at R-6.0 to R-6.5 per inch offers roughly 80% higher thermal resistance than EPS. This is why it dominates refrigerated truck body, cold storage, and RV insulation applications. When our engineers work with vehicle manufacturers, the conversation almost always starts here — PU lets you hit target R-values at thinner profiles, preserving payload capacity and interior space.

The weight advantage compounds quickly. A 3″ PU panel (R-18) trails a 4″ XPS panel (R-20) by only 10% — nearly matching the thermal performance at 25% less thickness. Across a 500 sqft truck body envelope, that thickness reduction translates directly into lighter panels and more cargo volume. Our production line maintains ±0.5mm thickness tolerance, so assembly-fit issues from inconsistent panels are eliminated.

With fire-retardant additives, PU cores achieve a Class B fire rating, which satisfies most commercial building codes and vehicle homologation requirements. For projects demanding Class A, you will need to step up to mineral wool — but expect a significant weight penalty.

• R-Value per inch: 6.0–6.5
• Typical density: 2.0 pcf (32 kg/m³)
• Fire rating: Class B (with fire retardant)
• Best fit: Refrigerated truck bodies, cold storage walls and roofing, RV thermal envelopes, marine insulation

Mineral Wool (Rockwool) Core Panels

Mineral wool is the only core among these three that achieves a Class A fire rating — the non-negotiable requirement for facilities handling flammable goods, food processing plants requiring strict compliance, and public transit interiors. Its R-value sits at approximately 3.0 per inch, the lowest of the three, but fire safety often overrides thermal metrics in specification decisions.

The weight penalty is the primary reason vehicle engineers hesitate. Mineral wool core panels at 4″ thickness weigh approximately 4.43 psf (26/26 gauge) versus 2.62 psf for standard foam cores at the same profile — a 69% increase. On a dry freight body or RV where every kilogram counts against payload limits and fuel efficiency, that difference forces difficult trade-offs. Our data shows that switching from steel to GRP/FRP facings on mineral wool panels can recover 30–40% of that weight penalty, making fire-rated assemblies viable for weight-sensitive vehicle platforms.

• R-Value per inch: ~3.0
• Typical density: 4.0–6.0 pcf (64–96 kg/m³)
• Fire rating: Class A (ASTM E84 compliant)
• Best fit: Fire-rated walls, hazardous material enclosures, food-grade facilities, public transit interiors

Core Selection Decision Logic

The selection process is not about finding the “best” core — it is about identifying which constraint binds your project first. If thermal performance per unit of thickness is the priority, PU wins decisively. If fire compliance is non-negotiable, mineral wool is the only valid option. If budget is the primary driver and thermal demands are moderate, EPS fills the role at the lowest material cost.

We manufacture all three core types on the same production line with continuous thickness monitoring, so switching between cores mid-order does not require a separate supplier qualification. Our engineers run experimental testing against your specific data standards before production begins, ensuring the composite panel meets both the thermal and structural requirements of your platform — whether that is a refrigerated truck body, an RV wall assembly, or a marine bulkhead.

Custom Thickness Solutions for OEM Production

Our production line maintains ±0.5mm thickness tolerance across custom sandwich panels from 10mm to 200mm, with continuous monitoring on a 1,700+ sqm daily output line.

Defining Your Panel Stack-Up for OEM Production

Specifying custom panel dimensions for vehicle production requires more than selecting a target thickness. We require engineers to define the complete stack-up: facing material and gauge on both skins, core material and density, and the total assembled thickness. Our engineers then run experimental testing against your data standards before production begins. This prevents the most common failure mode we see—thickness inconsistency causing assembly rejects on the vehicle line.

For specialized vehicle applications, the specification process starts with your weight budget and thermal requirements working backward to the optimal panel configuration. A refrigerated truck body requiring R-24 thermal performance at 4″ (102mm) thickness can achieve that with PU foam core at R-6.0/inch—but if your weight ceiling demands GRP facings instead of 26-gauge steel, the core density may need adjustment to maintain structural rigidity.

Critical Specification Parameters

When submitting a custom panel specification to our engineering team, include the following parameters. Incomplete specs are the single largest cause of production delays we encounter.

• Total Thickness: Range available from 10mm to 200mm (0.39″ to 7.87″), held to ±0.5mm tolerance during continuous production.
• Facing Material: Specify GRP/FRP, CFRT, Aluminum, Steel, Stainless Steel, PVC, Plywood, or Aluzinc for each skin. GRP/FRP facings reduce facing weight by 30–40% compared to steel equivalents.
• Core Material and Density: PU (R-6.0–6.5/inch), XPS (R-5.0/inch), PET (R-4.0/inch), PVC, PMI, EPP, MPP foams, or PP/Aramid/PC honeycomb. Core density directly impacts both weight per sqm and compressive strength.
• Panel Width and Length: Maximum standard width is 42″ (1067mm). Custom lengths cut to your BOM requirements.
• Application Environment: Temperature range, moisture exposure, fire rating requirement (Class A mineral wool vs. Class B PU with fire retardant), and any vehicle homologation weight limits.

Weight and Thermal Trade-Offs by Facing Selection

The facing selection drives weight more than most engineers anticipate. A 4″ (102mm) panel with 26/26 gauge steel facings weighs approximately 2.62 psf (12.8 kg/m²). Upgrading to 22/22 gauge increases that to 3.63 psf (17.7 kg/m²)—a 38% weight penalty for structural capacity that many vehicle applications do not require. Our GRP/FRP facing option at the same 4″ thickness with PU core typically comes in under 1.80 psf (8.8 kg/m²), which is where vehicle manufacturers find meaningful fuel efficiency gains across 500+ sqft of wall and roof area.

For fire-rated assemblies, the calculation shifts. Mineral wool core panels at 4″ with 26/26 gauge facings weigh approximately 4.43 psf (21.6 kg/m²)—a 69% weight penalty over standard foam core. If your vehicle application requires Class A fire rating, we recommend specifying our GRP-faced mineral wool panels where the lighter facing partially offsets the core weight increase, or evaluating whether a PU core with fire retardant additives at Class B rating meets your regulatory threshold.

Our Specification Workflow

Once you submit your panel requirements, our engineering team follows a structured process. We have refined this over 15 years of production to minimize the risk of thermal underperformance or dimensional non-conformance at your assembly plant.

• Step 1 — Requirement Validation: Our engineers review your thermal (R-value), structural, and weight specifications against our material database. We flag conflicts—for example, specifying a 2″ panel with R-20 thermal performance is physically impossible with current foam core technology.
• Step 2 — Experimental Testing: We produce sample panels and test to your required data standards. This is where we verify that the actual thickness tolerance, core density, and facing bond strength meet your assembly requirements.
• Step 3 — Production Specification Lock: Once samples are approved, we lock the material bill—facing gauge, core material, core density, and adhesive system. Our continuous production line monitors thickness at line speed, maintaining the ±0.5mm tolerance across the full 1,700+ sqm daily output.
• Step 4 — Ongoing QC Reporting: For OEM accounts, we provide thickness and weight data per production batch, so your incoming QC team can verify conformance without re-measuring every panel.

To begin a specification discussion, provide your target thermal performance (R-value or U-value), maximum panel weight per square meter, required fire rating class, and total project square footage. Our international engineering team—fluent in English, French, Russian, Japanese, and Korean—responds within 24 hours with a preliminary material recommendation and cost estimate. This direct engineering-to-engineering exchange eliminates the specification errors that typically delay composite panel orders by weeks.

Conclusion

For vehicle applications, PU foam core with GRP facings is the clear spec. At 4″ thickness, PU delivers R-24 — 66% more thermal resistance than EPS at R-14.4 in the same footprint. Swap steel facings for GRP on a 500 sqft truck body and you shed roughly 500 lbs while keeping identical insulation performance.

Before you finalize your BOM, request samples at your exact target thickness with the ISO-certified R-value test report for that specific core density — not a generic product sheet. Run your own thermal cycling test on those samples across your vehicle’s full operating temperature range. That lab number goes straight into your homologation filing, so verify it on your bench first.

Frequently Asked Questions