Knauf Earthwool Dritherm 32 Cavity Wall Insulation Slab 1200mm x 455mm

Knauf Earthwool Dritherm 32 Cavity Wall Insulation Slab is a glass mineral wool product engineered for use in external wall cavities. It is manufactured using Knauf’s ECOSE® Technology, a bio-based binder that gives the slab a softer feel, low dust levels, and a neutral odour. The slabs have a natural pale brown colour and a uniform fibre texture that ensures consistent coverage within masonry wall systems.

This insulation provides dependable thermal efficiency, helping reduce heat loss and improve energy performance in residential and commercial buildings. Its semi-rigid structure allows the slab to friction-fit between wall ties, creating a continuous layer without gaps. The product also resists moisture transfer, supporting proper cavity wall drainage and long-term performance.

Ideal for new builds and extensions, Earthwool Dritherm 32 supports compliance with building regulations, improves comfort, and contributes to a more stable indoor environment. It naturally incorporates acoustic absorption properties, helping reduce external noise transmission across cavity walls.

Installation Guide:

• Prepare the wall cavity and ensure it is free from debris
• Start placing slabs from the bottom of the wall upward
• Fit slabs tightly between wall ties with no gaps
• Trim using a sharp insulation knife where adjustments are needed
• Ensure all joints are butted firmly for a continuous insulation layer
• Follow approved cavity wall tie spacing and building regulations
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What is the difference Between Knauf Dritherm 32 and Dritherm 37?

1. Knauf Dritherm 32 – The Premium Choice for Maximum Home Efficiency

Best-in-Class Thermal Performance (λ = 0.032 W/mK): If you’re aiming for a more energy-efficient home, Dritherm 32 gives you the strongest thermal performance in the Dritherm range. Its ultra-low λ-value helps achieve better U-values, meaning warmer winters, lower bills, and a more future-proof property.

Ideal for All Exposure Zones & High-Spec Builds: Perfect for homeowners wanting higher comfort and builders targeting premium insulation, Dritherm 32 performs reliably in all exposure zones, including severe and very severe. It’s designed for new builds, high-performance renovations, and full-fill cavity wall systems where thermal excellence matters.

Best Long-Term Value & Performance: If you’re aiming for a smarter, higher-performance upgrade, you’ll find yourself drawn toward Dritherm 32, becuase it delivers stronger heat retention, improved SAP performance, and long-term energy efficiency, making it the standout choice for most modern builds.

2. Knauf Dritherm 37 – A Reliable, Cost-Smart Solution for Standard Homes

Strong Insulation at a More Budget-Friendly Cost (λ = 0.037 W/mK): Dritherm 37 still offers excellent thermal efficiency, especially for everyday residential projects. It uses the same ECOSE® Technology, glass mineral wool, and A1 non-combustible rating, giving homeowners dependable performance at a lower cost.

Perfect for Standard 100–150mm Cavities: For typical cavity wall homes, extensions, or renovations where ultra-low λ-values aren’t essential, Dritherm 37 comfortably meets Building Regulations Part L and provides consistent thermal and acoustic comfort.

Best Balance of Price vs. Performance: If budget is the priority but you still want reputable Knauf quality, Dritherm 37 is a safe, proven choice. It keeps your project affordable without compromising on performance or fire safety.

Both insulation slabs deliver trusted Knauf performance, but if you’re building for higher efficiency, stronger energy ratings, and long-term savings, Dritherm 32 is the superior investment. And if you need a cost-effective insulation solution that still delivers reliable comfort and compliance, Dritherm 37 is the smart value option.