Choosing the right core material for a sandwich panel is a critical decision that affects the performance, cost, and success of your construction project. The three most commonly used materials are EPS (Expanded Polystyrene), PU (Polyurethane), and Rockwool (stone mineral wool).
Each material has unique characteristics that make it suitable for certain applications. Understanding the differences between the three will help you make the right decision based on your project needs, budget, and technical requirements.
In this guide, you will learn:
- A detailed technical comparison of EPS vs PU vs Rockwool
- Cost and ROI analysis for each material
- Recommended applications by project type
- Environmental and sustainability considerations
- Real case studies with measured results
Introduction to Sandwich Panel Core Materials
EPS (Expanded Polystyrene)
What is EPS? EPS is a foamed plastic material made from polystyrene beads that are heated and expanded. It is lightweight, has a closed-cell structure, and is known as an effective thermal insulator at an affordable price.
Basic characteristics:
- Density: 10-30 kg/m³
- Thermal conductivity (λ): 0.032-0.038 W/mK
- Working temperature: -40°C to +80°C
- Structure: Closed-cell
PU (Polyurethane)
What is PU? PU is a polymer material formed by a chemical reaction between polyol and isocyanate. It has a very dense closed-cell structure, which makes it a high-performance thermal insulator.
Basic characteristics:
- Density: 30-50 kg/m³
- Thermal conductivity (λ): 0.022-0.028 W/mK
- Working temperature: -200°C to +120°C
- Structure: Very dense closed-cell
Rockwool (Mineral Wool)
What is Rockwool? Rockwool is a mineral fibre material made from basalt rock melted at high temperature (around 1600°C) and spun into fibres. It is known as a very good acoustic and fire-resistant insulator.
Basic characteristics:
- Density: 60-180 kg/m³
- Thermal conductivity (λ): 0.035-0.040 W/mK
- Working temperature: up to +1000°C
- Structure: Irregular fibres (open structure)
Detailed Technical Comparison
- Thermal Insulation Performance
Thermal Conductivity (λ-value)
- PU: 0.022-0.028 W/mK (LOWEST λ)
- EPS: 0.032-0.038 W/mK (GOOD)
- Rockwool: 0.035-0.040 W/mK (FAIR)
Thickness needed for the same R-value:
- PU: 100mm = EPS: 140mm = Rockwool: 150mm
- Meaning: PU reaches the same insulation with the least thickness
Energy Efficiency:
- Buildings with PU save 15-25% more energy than with EPS
- Rockwool provides good thermal stability for high-temperature applications
- Acoustic Performance
Noise Reduction Coefficient (NRC):
- Rockwool: 0.90-1.00 (VERY GOOD)
- PU: 0.60-0.75 (GOOD)
- EPS: 0.30-0.50 (FAIR)
Sound Reduction (STC):
- Rockwool: STC 45-55 dB
- PU: STC 35-45 dB
- EPS: STC 25-35 dB
Specific applications:
- Rockwool: Recording studios, machine rooms, noisy factories
- PU: Offices, hotels, hospitals
- EPS: Warehouses, industrial buildings with a thermal priority
- Fire Resistance and Safety
Fire Classification:
- Rockwool: Class A1 (non-combustible)
- DOES NOT BURN
- PU: Class B-s1,d0 (hardly combustible) - with fire retardant
- EPS: Class E (combustible) - requires a special coating
Behaviour in a fire:
- Rockwool: Does not melt, does not produce toxic smoke
- PU: Can melt, produces toxic smoke (HCN, CO)
- EPS: Melts quickly, produces thick black smoke
Regulatory requirements:
- Tall buildings (>8 floors): Usually require Rockwool
- Public buildings: Strict requirements for PU and EPS
- Industry: Depends on the fire risk
- Structural Strength
Compressive Strength:
- PU: 150-300 kPa (HIGHEST)
- Rockwool: 40-100 kPa (FAIR)
- EPS: 70-150 kPa (GOOD)
Rigidity:
- PU: Very rigid, dimensionally stable
- EPS: Fairly rigid, can experience creep
- Rockwool: Flexible, can be compressed
Load Resistance:
- EPS: Suitable for walls with normal loads
- Rockwool: Needs additional support for high loads
- Moisture Resistance
Water Absorption:
- PU: <3% volume (VERY GOOD)
- EPS: 2-4% volume (GOOD)
- Rockwool: >5% volume (VULNERABLE)
Effect of moisture on performance:
- PU: Insulation performance stays stable
- EPS: Insulation performance can drop when wet
- Rockwool: Loses 50%+ of its insulation performance when wet
Wet/humid applications:
- PU: Swimming pools, cold storage, wet areas
- EPS: With good waterproofing protection
- Rockwool: Avoid applications with high humidity
Cost and ROI Analysis
Material Cost per m² (2026)
100mm thickness:
- EPS: Rp 150,000
- Rp 250,000
- PU: Rp 300,000
- Rp 450,000
- Rockwool: Rp 400,000
- Rp 600,000
Factors that affect the price:
- Material density
- Panel thickness
- Surface finishing
- Purchase volume
- Project location
Installation Cost
Level of difficulty:
- EPS: Easy (lightest)
- PU: Moderate (precision needed)
- Rockwool: Difficult (heavy, needs special tools)
Installation time:
- EPS: 20-30 m²/day/person
- PU: 15-25 m²/day/person
- Rockwool: 10-15 m²/day/person
Return on Investment (ROI)
Annual energy savings:
- PU: 25-35% compared with EPS
- EPS: 15-25% compared with conventional construction
- Rockwool: 10-20% (depending on the application)
Payback period:
- PU: 3-5 years (for cold storage applications)
- EPS: 2-4 years (for chilled warehouses)
- Rockwool: 5-8 years (for special applications)
Property value:
- Buildings with PU are valued 5-10% higher
- Green building certification increases value
Recommended Applications by Project Type
- Cold Storage & Freezer Rooms
Recommendation: PU (First Choice)
- Reason: Lowest λ-value, high moisture resistance
- Thickness: 100-150mm
- Working temperature: -25°C to +5°C
- Examples: Food warehouses, industrial freezers, chiller rooms
Alternative: EPS
- For: Medium-temperature cold storage (0°C to +10°C)
- Consideration: Limited budget, temperatures not extreme
- Warehouses & Industrial Buildings
Recommendation: EPS (Most Economical)
- Reason: Cost-effective, fast installation
- Thickness: 75-100mm
- Applications: Logistics warehouses, factories, workshops
Alternative: PU
- For: Temperature-controlled warehouses
- Consideration: Energy efficiency matters more than initial cost
- Commercial Buildings (Offices, Malls, Hotels)
Recommendation: PU or Rockwool
- PU: For maximum energy efficiency
- Rockwool: For acoustics and fire safety
- Combination: PU for ceilings, Rockwool for partition walls
- Special Buildings
Studios & Acoustic Rooms: Rockwool
- Priority: Maximum sound reduction
Chemical & Hazardous Plants: Rockwool
- Priority: Fire resistance, high-temperature stability
Hospitals & Laboratories: PU
- Priority: Hygiene, moisture resistance, insulation
Environmental & Sustainability Considerations
Carbon Footprint
Production:
- EPS: 2.5-3.5 kg CO₂/kg of material
- PU: 3.5-4.5 kg CO₂/kg of material
- Rockwool: 1.2-1.8 kg CO₂/kg of material (LOWEST)
Embodied Energy:
- Rockwool: 16-20 MJ/kg
- EPS: 88-110 MJ/kg
- PU: 95-120 MJ/kg
Recycling & End-of-Life
Recyclability:
- EPS: 70-80% recyclable
- PU: 50-60% recyclable (more difficult)
- Rockwool: 90-95% recyclable (HIGHEST)
Waste processing:
- EPS: Can be shredded for secondary products
- PU: Can be turned into RDF (Refuse Derived Fuel)
- Rockwool: Can be reused as aggregate
Green Certification
Materials that qualify:
- LEED: All (with different requirements)
- GREENSHIP: PU and Rockwool are preferred
- EDGE: Depends on energy efficiency
Real Case Studies
Case 1: Vegetable Cold Storage (Bogor)
Project: 500m² cold storage for vegetables Material chosen: PU 150mm Results:
- Stable temperature: 2°C ±0.5°C
- Energy consumption: 35% lower than estimated
- ROI: 3.2 years
- Humidity: 85% RH controlled
Case 2: Logistics Warehouse (Tangerang)
Project: 2,000m² logistics warehouse Material chosen: EPS 100mm Results:
- Material cost: 40% cheaper than PU
- Installation: Finished 7 days faster
- Inside temperature: 5-8°C cooler than outside
- Satisfaction: High for a limited budget
Case 3: Recording Studio (Jakarta)
Project: 100m² professional recording studio Material chosen: Rockwool 100mm + PU 50mm (hybrid) Results:
- STC: 52 dB (above specification)
- Acoustics: Very good across all frequencies
- Temperature: Stable with minimal air conditioning
- Cost: 25% higher, but justified by the quality
Guide to Choosing the Material
Decision Matrix
Key questions:
- What is the main priority? (Cost/Energy/Acoustics/Fire)
- What budget is available?
- What are the environmental conditions of the project?
- What are the regulatory requirements?
- How long is the building expected to last?
Selection Flowchart
If you want a quick decision, use this simple flow:
- Cost priority: choose EPS.
- Energy efficiency priority: choose PU.
- Acoustic priority: choose Rockwool.
- Fire resistance priority: choose Rockwool or a PIR/Rockwool system that meets the regulations.
- Mixed needs: consider a hybrid system.
Hybrid Systems
Effective combinations:
- PU + Rockwool: PU ceiling (insulation) + Rockwool walls (acoustics + fire)
- EPS + Coating: EPS with a fire-resistant coating for a limited budget
- Layered system: Multiple layers for maximum performance
FAQ
Which one lasts the longest?
Answer: PU has the longest service life (25-30 years) with consistent performance. EPS can degrade after 15-20 years. Rockwool is physically very durable but can lose performance when exposed to moisture.
Can the materials be combined?
Answer: Yes, hybrid systems are becoming more popular. Example: PU for thermal insulation + Rockwool for acoustics. However, the design should be done by professionals to avoid problems such as interstitial condensation.
Which one is the most environmentally friendly?
Answer: Rockwool has the lowest carbon footprint and the highest recycling rate. However, also consider energy efficiency over the service life
- PU can offset its production emissions through energy savings.
What about newer materials such as PIR?
Answer: PIR (Polyisocyanurate) is a PU variant with better fire performance. It has a similar λ-value (0.022-0.026 W/mK) but a higher fire classification (B-s2,d0 or better). The price is 10-15% higher than standard PU.
Conclusion
No single material suits every application. The choice between EPS, PU, and Rockwool should be based on a thorough analysis of:
- Project needs: Thermal, acoustic, or fire priority?
- Budget: Initial cost vs long-term operating cost
- Environment: Site conditions and sustainability requirements
- Regulations: Building codes and safety requirements
General recommendations:
- EPS: The economical choice for warehouses and industrial buildings
- PU: The right investment for maximum energy efficiency
- Rockwool: The strong option for safety and acoustics
Remember: Consult a materials expert before deciding. Investing in a professional analysis can save large costs in the long run.
Need help choosing the right material? Our technical team is ready to analyse your project and recommend a suitable solution. Get a consultation.
Next Steps for Your Project
If you are still weighing which panel specification suits you, see our sandwich panel catalogue to compare the available options. If you want to discuss your project needs, panel thickness, or installation details, you can also contact our team directly so the recommendation is more accurate.
