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Knauf DriTherm Cavity Slab

Insulate with the best or lose heat like the rest, that's what we say. 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 performance 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. The slabs boast an impressive A1 non-combustible classification. 

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What Are DriTherm Cavity Slabs?


Empty cavity walls are one of the biggest culprits when it comes to heat loss and air movement within your home. That's why it is absolutely imperative to fill them, in order to retain the heat in your home and cut the cost of energy bills.

Knauf DriTherm Cavity Wall Insulation Slabs are one of your home's biggest defenders against ice-kissed winter winds and teeth-chattering temperatures. Insulate with the best or lose heat like the rest, that's what we say.
We stock popular Knauf Earthwool DriTherm 32 and Knauf Earthwool DriTherm 37 slabs. These full-fill Knauf cavity slabs are a high-performing thermal insulation solution designed for use between masonry cavity walls in residential and commercial buildings.

Simply put, Knauf Insulation DriTherm cavity slab is made from glass mineral wool, making it a member of the fibreglass insulation family. Made using Knauf's unique ECOSE technology, Knauf DriTherm cavity insulation slabs are cotton wool soft, despite being made from recycled glass mineral wool - meaning the only itch these slabs will give you is the itch to buy more. The number classified within the slab title is a reference to the product's thermal conductivity value in terms of W/mK whilst the 'Dri' refers to the slab's water repellent additive, added to maximise its overall thermal performance. Knauf Earthwool DriTherm is conveniently cut at 455mm wide in line with standard wall tie spacings, producing a neatly closed joint with adjacent slabs and eliminating air gaps.

What Is Full-Fill Insulation?


Knauf Insulation Earthwool DriTherm cavity slabs are full-fill solutions. What is full-fill solution exactly? It really is as simple as it sounds. Partial-fill cavity insulation only fills part of the space between external masonry cavity walls, whilst full-fill products fully fill the space perfectly.

Knauf DriTherm 32


Knauf DriTherm 32
semi-rigid insulation is named after its thermal conductivity of 0.032 W/mK, meaning that it offers superb protection against heat loss. Similar to the other sized slabs in its range, DriTherm 32 is purposed to reduce the amount of heat that you lose through your masonry walls. Each slab has dimensions of 1200mm x 455mm. At 455mm wide, these slabs are just right for standard vertical wall tie spacings. The slabs are also water repellent and BBA certified for use in all exposure zones, including those in very severe areas.

DriTherm cavity slabs 32 are both doughy and soft, easy to handle, and significantly more environmentally friendly than normal fibreglass slabs.

Knauf DriTherm 37


Earthwool DriTherm 37
also takes its name from its thermal performance. With a thermal conductivity value of 0.037 W/mK, these slabs are less thermally efficient than DriTherm 32 cavity slabs, however, they can still be used in buildings that are up to 12m high due to their A1 (non-combustible) rating on the Euroclass scale. 

Despite their difference in conductivity, full-fill DriTherm 37 slabs are just as simple to install as DriTherm 32. DriTherm 37 slabs will knit together to eliminate air gaps and enhance the slab's insulating properties. They are also non-hygroscopic; meaning they do not retain moisture or promote the growth of bacteria or fungi.

Frequently Asked DriTherm Cavity Slab Questions

What Are the Benefits of DriTherm Cavity Slabs?

One of the biggest advantages of Knauf Insulation DriTherm cavity slabs is the fact that they are specifically designed to be compatible with standard vertical wall ties, banishing the need for retaining discs. The slabs are rigid and compact; eliminating air pockets and the need for expensive equipment. It has very high levels of thermal resistance allowing compliance with the relevant Building Regulations

Another reason to consider DriTherm is its superior environmental sustainability. Thanks to its low environmental impact, it is eco-friendly and classified as zero ODP and zero GWP. The slabs are made from up to 80% recycled glass, minimising the need for mineral raw materials. Better yet, Dritherm incorporates the environmentally friendly ECOSE technology: a bio-binder that is made from natural, raw materials that are 70% less intensive to create than typical binders. Such technology enhances the environmental credentials without impacting the thermal, fire or acoustic performance.

Are Knauf DriTherm Cavity Slabs Fireproof?

Knauf Insulation DriTherm 32 and Knauf Insulation DriTherm 37 slabs are rated A1 on the Euroclass scale. The European Reaction to Fire classification system (Euroclasses) is the EU common standard for assessing the qualities of building materials in the event of a fire.

Insulation materials are measured against up to five tests and given a rating from A1 (non-combustible) to F (combustible). With an A1 rating, these slabs achieve the highest possible certification on the Euroclass scale - which in essence, means they provide excellent protection against fire and minimise the risk of fire spreading.

Is Knauf Cavity Wall Insulation Waterproof?

Although Knauf Insulation DriTherm 32 and DriTherm 37 cavity slabs are water-resistant (thanks to their water repellent additive), 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.

Both the DriTherm cavity slab 32 and DriTherm cavity slab 37 have a water vapour resistivity of 5.00MNs/g.m. Earthwool slabs are non-hygroscopic and are therefore approved to use in all exposure zones, as they will not absorb moisture. Another welcome benefit of the water-resistant binder used in Knauf slabs is that it eliminates the chance of rot, vermin, or fungus.

For this reason, we highly recommend Knauf slabs for people who live in high-rainfall areas. People choose Knauf Earthwool slabs when they need full-fill insulation that has a long lifespan. The nature of full-fill insulation slabs further ensures that they do not sag or droop over time - promising maximum protection for the lifetime of your build.

How to Cut Knauf Insulation DriTherm Cavity Slabs?

Knauf Earthwool wool cavity slabs are very light and malleable. You can simply use a sharp serrated knife to slice through Dritherm 32 and DriTherm 37. 

Always ensure you take proper safety precautions. Before you cut and fit into masonry cavity external walls, we recommend wearing goggles, aprons, and even protective glasses. If you are concerned about safety precautions, always consult with a professional.