Expanded Cork Granules are a lightweight, breathable natural insulation material manufactured from thermally expanded cork oak bark. During production, the cork granules are expanded using heat and steam only, without synthetic binders or chemical additives. The natural resins within the cork (suberin) bind the granules together while maintaining high vapour permeability, moisture resistance, and thermal performance.
Because the material remains fully vapour open and hygroscopic, expanded cork granules are particularly suitable for breathable retrofit projects, traditional masonry buildings, timber floors, lofts, roof spaces, and cavity insulation applications where moisture-safe construction is important.
The granules combine thermal insulation, acoustic absorption, moisture buffering, and sustainability within a single natural insulation material.
Technical Data
| Property | Value |
|---|---|
| Material | Expanded cork granules |
| Thermal Conductivity (λ) | 0.040–0.041 W/mK |
| Density | Approx. 60–70 kg/m³ |
| Vapour Diffusion Resistance (μ-value) | Approx. 5–10 |
| Fire Classification | Euroclass E |
| Moisture Behaviour | Vapour open & moisture regulating |
| Specific Heat Capacity | High thermal mass |
| Composition | 100% natural expanded cork |
| Binder | Natural cork resins only |
| Installation Type | Loose fill |
Key Benefits
High Thermal Performance
With a thermal conductivity of approximately λ = 0.040–0.041 W/mK, expanded cork granules provide strong thermal insulation while remaining fully breathable.
Vapour Open & Moisture Safe
The material remains highly vapour permeable and capillary active, allowing moisture vapour to diffuse safely through the structure while supporting inward and outward drying.
Naturally Moisture Resistant
Unlike many loose-fill insulation materials, cork is naturally resistant to:
- moisture,
- mould,
- fungal growth,
- and rot
due to the presence of suberin within the cork cell structure.
Excellent Acoustic Insulation
The cellular structure of cork naturally dampens:
- airborne sound,
- vibration,
- and impact noise,
making it suitable for floors, ceilings, and timber structures.
Excellent Summer Heat Protection
Cork has high thermal inertia and heat storage capacity, helping reduce overheating during summer conditions.
Lightweight & Easy to Install
The granules are lightweight and free-flowing, making them particularly useful for:
- irregular voids,
- suspended timber floors,
- loft spaces,
- and difficult-to-access cavities.
Fully Natural & Sustainable
Expanded cork is:
- renewable,
- recyclable,
- biodegradable,
- and carbon negative,
with no synthetic binders or petrochemical additives.
Typical Applications
- Suspended timber floor insulation
- Loft insulation
- Roof void insulation
- Timber frame insulation
- Breathable cavity fill
- Acoustic insulation
- Breathable retrofit projects
- Heritage and conservation buildings
Why Use Expanded Cork Granules?
Traditional buildings rely on vapour diffusion and capillary drying to manage moisture safely. Impermeable insulation materials can interrupt this drying process and increase condensation risk within the structure.
Expanded cork granules differ because they remain:
- vapour open,
- hygroscopic,
- and moisture regulating.
This allows surrounding materials to continue drying naturally while still improving thermal performance and acoustic comfort.
The loose-fill format also makes cork particularly useful for:
- irregular voids,
- retrofit projects,
- and traditional timber floors
where rigid insulation boards may be difficult to install effectively.
Installation Overview
1. Preparation
Ensure cavities or voids are clean, dry, and appropriately contained prior to installation.
2. Installation
Granules are poured or blown into:
- floor voids,
- roof spaces,
- cavities,
- or timber frame systems.
3. Compaction Control
The material should be distributed evenly without excessive compaction to maintain thermal performance.
4. Membrane Integration
Expanded cork granules integrate well with:
- breathable membranes,
- wood fibre systems,
- lime plasters,
- and vapour-open construction assemblies.
5. Final Build-Up
Suitable beneath:
- suspended timber floors,
- breathable floor systems,
- roof structures,
- and vapour-open retrofit systems.
A Breathable Alternative to Synthetic Loose-Fill Insulation
Expanded cork granules provide a natural moisture-safe alternative to:
- EPS beads,
- synthetic loose-fill insulation,
- and petrochemical cavity insulation systems.
Because the material remains vapour open and moisture regulating, it supports:
- safer moisture movement,
- reduced condensation risk,
- improved acoustic comfort,
- and breathable low-energy construction.
This makes it particularly suitable for:
- traditional buildings,
- heritage retrofit,
- suspended timber floors,
- and moisture-sensitive structures.
