Roof Rock Wool Sandwich Panels, also called metal-faced composite panels, consist of two thin metal facing sheets bonded to a lightweight core material. The facing sheets are typically 0.4 mm to 0.8 mm thick and may be galvanized steel, color-coated steel, Al-Zn coated steel, or aluminum alloy. The core material is selected based on fire safety, thermal insulation, and budget requirements. Common core options are rock wool, rigid polyurethane (PU), and polystyrene (EPS). The facings and core are bonded with adhesive, forming a stressed-skin structure. The metal facings carry tensile and compressive forces, while the core transfers shear stress and keeps the facings separated, resulting in high flexural rigidity relative to panel weight.
Roof Rock Wool Sandwich Panels are commonly 50 mm to 200 mm thick with effective widths of 900 mm to 1000 mm. PU sandwich panels range from 30 mm to 100 mm thick with an effective width of 1000 mm. EPS sandwich panels are available from 50 mm to 250 mm thick with effective widths of 1150 mm or 1200 mm. Panel length is generally up to 12,000 mm, and custom lengths can be produced according to project requirements.
| Performance Indicator | Polyurethane (PU) Core | Rock Wool Core | Polystyrene (EPS) Core | Standard Reference |
|---|---|---|---|---|
| Core Density | ≥30 kg/m³ | ≥100 kg/m³ | ≥18 kg/m³ | JC/T 868 / 869 / 689 |
| Thermal Conductivity | ≤0.027 W/(m·K) | ≤0.045 W/(m·K) | ≤0.041 W/(m·K) | Measured at ambient temperature |
| Bond Strength | ≥0.09 MPa | >0.06 MPa | >0.1 MPa | Between facing and core |
| Combustion Performance | Class B1 | Class A (Non-combustible) | Class B2 | GB 8624 |
| Fire Resistance Rating | Not specified | ≥60 min for thickness ≥80 mm | Not specified | Verified by fire tests |
| Flexural Load Capacity | ≥0.5 kN/m at L₀/200 | ≥0.5 kN/m at L₀/250 | ≥0.5 kN/m at L₀/250 | Deflection limit |
| Common Thickness | 30–100 mm | 50–200 mm | 50–250 mm | Customizable |
| Effective Width | 1000 mm | 900–1000 mm | 1150–1200 mm | Standard widths |
The panel behaves like an I-beam. The metal facings act as flanges, carrying tensile and compressive stresses. The core acts as the web, transferring shear forces. Increasing core thickness raises flexural rigidity without adding significant weight because the core density is low. All three core types are required to meet a minimum flexural load capacity of 0.5 kN/m under the specified deflection limit. Rock wool and EPS panels are tested at L₀/250, while PU panels are tested at L₀/200.
Bond strength requirements vary by core type. EPS panels require a bond strength above 0.1 MPa, PU panels at least 0.09 MPa, and rock wool panels above 0.06 MPa. During peel testing, the core material remaining on the facing must be evenly distributed and cover at least 85% of the bonded area. This requirement helps confirm that the facings and core continue to work as a single unit.
Fire behavior is determined mainly by the core. Rock wool cores are non-combustible and provide a fire resistance rating of at least 60 minutes when thickness is 80 mm or more. PU cores can reach Class B1 flame-retardant rating. EPS cores are rated Class B2 and are limited to areas with low fire safety requirements. Project fire codes should guide core selection.
PU cores offer the lowest thermal conductivity at 0.027 W/(m·K) or less, followed by EPS at 0.041 W/(m·K) and rock wool at 0.045 W/(m·K). Selection should balance insulation targets, fire rating, and budget. For a given insulation requirement, PU panels can be thinner than EPS or rock wool panels.
Rock wool core panels are suitable for buildings that require non-combustible envelope materials, such as industrial plants with high fire risk, public buildings, cleanrooms, and areas where fire codes mandate Class A materials. They also provide good sound absorption, which is useful in noisy environments.
PU core panels are appropriate for projects where maximum thermal insulation is needed within limited thickness, such as cold storage, temperature-controlled warehouses, and energy-efficient buildings. Their B1 fire rating makes them acceptable in many applications, but local fire regulations should be confirmed.
EPS core panels are an economical option for buildings with low fire safety requirements, such as temporary structures, agricultural buildings, and some warehouses. They provide good insulation at a lower cost, but their B2 rating restricts use in occupied or high-risk areas.
Rock wool is the only non-combustible option among the three and provides the highest fire resistance. PU can achieve B1, while EPS is B2. For buildings with strict fire codes, rock wool is usually required.
Yes, sandwich panels can be used for both walls and roofs, but roof panels may require additional features such as stronger profiles, better drainage design, and higher wind uplift resistance. Confirm with the manufacturer that the selected panel meets roof load requirements.
PU offers better thermal insulation per unit thickness and higher bond strength, but costs more. EPS is lighter and cheaper. If insulation targets can be met with a thicker EPS panel, it may be the more economical choice. Thermal calculations should guide the decision.
Relevant standards include JC/T 868 for metal-faced polyurethane sandwich panels, JC/T 869 for metal-faced rock wool sandwich panels, and JC/T 689 for metal-faced polystyrene sandwich panels. Project specifications and acceptance criteria should refer to these documents.
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