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Updated Winter 2025
When building or upgrading a home, choosing the right cavity wall insulation is essential for achieving top-tier thermal efficiency and long-term energy savings. In this guide, we compare three of the UK’s most popular full-fill cavity insulation boards — Kingspan K106 90mm Cavity Board, Recticel Eurowall+ Full Fill 90mm, and EcoTherm Eco-Cavity Full Fill 90mm.
All three are designed for full-fill cavity wall applications, providing high performance, moisture resistance, and compliance with Building Regulations Part L.
Full-fill insulation completely fills the cavity between your inner and outer masonry walls, leaving a small residual cavity (around 10 mm) to manage moisture.
| Product | Thermal Conductivity (λ) | Board Size / Thickness | Material | Features |
|---|---|---|---|---|
| Kingspan K106 90mm | ≈ 0.019 W/m·K | 1200 × 450 × 90 mm | Phenolic foam core | Outstanding thermal efficiency; 10 mm residual cavity; premium product |
| Recticel Eurowall+ Full Fill 90mm | ≈ 0.022 W/m·K | 1200 × 450 × 90 mm | PIR rigid foam | Tongue-and-groove edges on all sides; tight fit reduces cold bridges |
| EcoTherm Eco-Cavity Full Fill 90mm | ≈ 0.022 W/m·K | 1200 × 450 × 90 mm | PIR rigid foam | Affordable, fibre-free, foil-faced, great value for large projects |
The Kingspan K106 Full Fill Cavity Board is a high-performance phenolic insulation board with an ultra-low thermal conductivity of 0.019 W/m·K. It delivers exceptional U-values in a slim build-up — perfect for projects where space or wall thickness is limited.
Ideal for: Premium new builds and energy-conscious projects requiring the best performance in the smallest footprint.
The Recticel Eurowall+ Full Fill 90mm Insulation Board offers a superb balance of performance and practicality. Its tongue-and-groove edges on all four sides ensure an easy, gap-free fit that limits cold bridging and air leakage.
Ideal for: Builders who prioritise ease of installation and reliable, consistent results across multiple plots.
The EcoTherm Eco-Cavity Full Fill 90mm Board is a cost-effective choice that still meets stringent performance standards. Made from rigid PIR foam and foil-faced on both sides, it offers robust thermal resistance and excellent long-term stability.
Ideal for: Budget-friendly projects where strong energy performance and compliance are still required.
| Scenario | Best Option |
|---|---|
| Maximum energy efficiency per mm thickness | Kingspan K106 90mm |
| Most installer-friendly board | Recticel Eurowall+ Full Fill 90mm |
| Best value for money | EcoTherm Eco-Cavity Full Fill 90mm |
Choosing between Kingspan K106, Recticel Eurowall+, and EcoTherm Eco-Cavity ultimately depends on your project priorities:
All three are BBA-certified, moisture-resistant, and suitable for full-fill cavity wall construction with a 10 mm residual cavity. The main differences come down to thermal conductivity (λ-value) and budget. Each offers outstanding insulation, long-term durability, and compliance with modern energy standards — ensuring lower heating costs and a warmer, more efficient home.
