Mineral Wool vs EPS Boards for External Wall Insulation (EWI)
Mineral Wool vs EPS Boards for External Wall Insulation (EWI)
When upgrading your property with an External Wall Insulation (EWI) system, one of the most important choices is the type of insulation board. The two most common options in the UK are EPS (expanded polystyrene) and mineral wool.
Both materials are effective for reducing heat loss and improving energy efficiency, but they perform differently in fire safety, cost, moisture management, and installation. This guide will help you understand which insulation board is best for your project.
What Are EPS Boards?
Expanded Polystyrene (EPS) boards are lightweight rigid foam panels made by expanding polystyrene beads.
✅ Benefits of EPS insulation:
- Excellent thermal performance per thickness
- Lightweight and quick to install
- Water-resistant with closed-cell structure
- Budget-friendly compared to mineral wool
⚠️ Considerations:
- Combustible material (though usually fire-retarded and safe when rendered)
- Less effective at soundproofing
EPS is often chosen for domestic EWI projects due to its affordability and ease of handling.
What Are Mineral Wool Boards?
Mineral Wool (or Rockwool) is manufactured from melted rock or slag, spun into fibres, and pressed into dense boards.
✅ Benefits of mineral wool insulation:
- 100% non-combustible — ideal for fire safety
- Breathable — helps prevent condensation and damp
- Excellent acoustic insulation
- Long-lasting and durable
⚠️ Considerations:
- Heavier and more difficult to install
- Typically more expensive than EPS
Mineral wool is often used in multi-storey buildings or high-risk properties where fire safety is critical.
EPS vs Mineral Wool: Key Comparison
| Factor | EPS Boards | Mineral Wool Boards |
|---|---|---|
| Thermal Performance | Excellent insulation with less thickness | Strong, may need thicker boards |
| Fire Safety | Combustible, though treated with retardants | Non-combustible, superior safety |
| Moisture Management | Water-resistant, low breathability | Vapour-permeable, prevents damp |
| Acoustic Performance | Limited soundproofing | Excellent sound absorption |
| Installation | Lightweight, easy to cut & fix | Heavier, needs stronger fixings |
| Cost | More affordable | Higher cost |
Which Insulation Should You Choose?
- ✅ Choose EPS if your project is cost-sensitive, you need fast installation, and fire regulations allow EPS use.
- ✅ Choose Mineral Wool if you need maximum fire safety, better breathability, or superior sound insulation.
Both materials perform well in EWI systems — your choice depends on project priorities and building regulations.
Final Thoughts
At Renders World, we supply top-quality insulation boards and render systems for every type of project. Whether you’re looking for affordable EPS boards or premium mineral wool insulation, we can provide the right materials and guidance.
👉 Explore our full range of EWI systems and insulation boards today, or contact our team for expert advice on choosing the right solution for your property.
