Knauf Insulation Slab

Regulate your home's temperature with Knauf insulation slabs. Knauf insulation slabs are made up of either glass wool or rock mineral wool; both of which feature a random fibre structure which traps thousands of air pockets, making them perfect heat and sound absorbers. All Knauf insulation slabs are classed as A1 non-combustible, which is the highest fire classification possible. All slabs we sell are manufactured using Knauf Insulation's unique bio-based binder, ECOSE Technology.

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Knauf Earthwool DriTherm Cavity Wall Insulation Slab

Knauf DriTherm Cavity Wall Insulation Slabs are semi-rigid or rigid slabs of non-combustible, water-repellent, glass mineral wool. Knauf DriTherm cavity slabs offer excellent thermal and acoustic insulation in masonry cavity external walls and can be used in buildings up to 12m in any exposure zone, as well as multi-story applications up to 25 metres tall, due to the fact they they do not absorb moisture. 

Although Knauf Insulation DriTherm 32 and DriTherm 37 cavity slabs are water-resistant (thanks to their water repellent additive, as implied by the 'Dri'), this does not mean that they are waterproof. Whilst the slabs are able to resist the penetration of water to a certain degree, they are not completely impenetrable.

Manufactured using Knauf's unique ECOSE technology, Knauf DriTherm cavity insulation slabs are buttery soft (no more itch!) and provide superb protection for the lifetime of your build. Boasting an impressive A1 non-combustible classification, these slabs also inhibit the spread of fire and reduce potential widespread damage to a building.

Knauf Earthwool Building Slabs Rocksilk (RS) Range

Rocksilk Slab is a high-performance, water-resistant, rock mineral wool slab. Its fire resistance removes the need for fire barriers, giving simple, quick and economical insulation for external wall insulation systems. Earthwool Building Slabs are non-combustible and are manufactured using Knauf Insulation's revolutionary ECOSE Technology.

Earthwool Building RS Slabs are manufactured in different densities and designed for use in a variety of applications including: 

  • Internal Partitions
  • Timber and Metal Studs
  • In between Timber Rafters and Floor Joists. 


An alternative slab with acoustic properties is Rockwool RWA45 100mm, which is a popular choice amongst our customers.

Knauf Insulation Rocksilk Flexible Slab

Rocksilk flexible slab is a versatile thermal, acoustic and roof insulation rock mineral wool slab that is exclusively designed to friction fit in multiple thermal and acoustic applications. This lightweight slab is designed to provide maximum fire protection and insulation to your home as it is free from the traditional method of petro-based chemicals, which are usually used in other insulation products.

This multi-purpose product can be applied in general thermal, acoustic and roof insulation such as: 

  • Ground Floors
  • Internal Floors
  • Separating Floors
  • Pitched Roofs at Rafter Level
  • Internal Walls/Partitions
  • Light Steel Frame Walls
  • Timber Frame Walls


It can also be used for the fire protection of a loft conversion floor.

Frequently Asked Knauf Insulation Slab Questions

Mineral Wool Insulation vs Fibreglass

For many decades, fibreglass insulation (also known as glass wool insulation or glass mineral wool) was the standard for home construction. So what are the main drawbacks?

First off, fibreglass is sourced from non-renewable materials, specifically plastic reinforced with glass fibres. Fibreglass Insulation is made from up to 30% of recycled glass, like Knauf DriTherm 37 (which is specifically designed for installation in external masonry cavity walls). Secondly, fibreglass insulation has been linked to adverse health impacts, including irritating the skin, eyes, and respiratory system.


Let's consider the properties of each:

● Eco-friendly - Mineral wool is made of up to 80% recycled content, whereas fibreglass is only made from up to 30%.

● Weight - Mineral wool insulation slabs are far heavier than fibreglass slabs. They do not bend or sag as easily as fibreglass insulation slabs.

● Installation - Firm mineral wool slabs can friction-fit into place between studs and joists. Installing fibreglass can be more complicated because it requires staples and/or wires.

● Fire resistance - Both fibreglass and mineral wool insulation are classed as A1 non-combustible on the Euroclass scale, which means that they do not burn.

Will I Need Cavity Barriers When Full Filling With DriTherm Cavity Slabs? 

A full fill cavity with DriTherm Cavity Slabs will meet the requirements of the Building Regulations 2010, therefore cavity barriers will not be required (as the insulation fully fills the cavity). DriTherm Cavity Slabs have the highest Euroclass Classification, Euroclass A1 Reaction to Fire Classification, in accordance with BS EN 13501-1 : 2007. 

What Tools Will I Need To Use When Installing?

Knauf insulation slabs are very light and malleable. You can simply use a sharp serrated knife to slice through them. 

Always ensure you take proper safety precautions. Before you get into the swing of cutting and fitting, we recommend wearing goggles, aprons, and even protective glasses. If you are concerned about safety precautions, always consult with a professional.

What Do The Numbers On The Product Names Mean?

The numbers on the product names are related to the thermal conductivity of the product. So the lower the number, the better thermal performance that product will give. For example, in the DriTherm range, the "Therm 37" relates to the product's thermal conductivity value of 0.037 W/mK whilst the 'Dri' refers to the slab's water repellent additive, added to maximise its overall thermal performance.