Earthwool DriTherm Cavity Slabs are non-combustible, Glass Mineral Wool slabs, manufactured using our revolutionary ECOSEĀ® Technology and a water repellent additive (50-year guarantee on resisting the transmission of water), designed for use in external masonry cavity walls to provide a full-fill insulation solution which is installed as walls are being built. DriTherm Cavity Slabs represent no known threat to the environment and have zero ODP and zero GWP. The slabs are rot-proof, odorless, non-hygroscopic, do not sustain vermin, and will not encourage the growth of mould, fungi, or bacteria.

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Earthwool Dritherm glass mineral wool cavity slabs provide the thermal insulated of masonry cavity external walls and are installed to made to fit perfectly in the cavity.

  • Excellent thermal performance.
  • Manufactured using a water repellent additive
  • Fully fill the cavity to prevent mortar snots and prevent bridges
  • Slabs are sized to fit between wall ties without the need for retaining discs,
  • Quick and easy to install
  • British Board of Agreement approved for use in all exposure zones

Earthwool DriTherm Cavity Slabs are supplied in polythene packs which is designed for short-term protection. For long-term protection keep the product undercover, off the ground or indoors as they should not be left permanently exposed to the elements.


  • Generic BRE Green Guide Rating A+
  • A1 Euroclass Reaction to Fire classification

Earthwool Acoustic Roll is manufactured in accordance with:

  • BS EN 13162, ISO 50001 Energy Management Systems
  • OHSAS 18001 Occupational Health and Safety Management Systems
  • ISO 14001 Environmental Management Systems
  • ISO 9001 Quality Management Systems, as certified by Bureau Veritas.

More Information:

  • Slab Size: 75mm (3.28m2), 85mm (2.73m2), 100mm (3.28m2), 125mm (2.18m2), 150mm (2.18m2)
  • Masonry cavity walls
  • Glass Mineral Wool
  • Thermal Conductivity from 0.032 to 0.037 W/mK
  • Water Vapour Resistivity: 5.00MNs/g.m



Thickness (mm)Thermal Conductivity (W/mK)Thermal Resistance (m2K/W)Length (mm)Width (mm)Slabs (Per Pack)Area Per Pack (m2)

Dritherm 34 Installation Guide

Before you begin:

Step 1:

Install wall ties in the inner leaf at 600mm horizontal centres

For suspended timber floors, wall ties start a minimum of 200mm below the top surface of the ground floor perimeter insulation upstand. Place the wall ties 900mm apart.

Continue constructing the inner leaf up to the next wall tie course. (450mm above the previous inner leaf). The next course of wall ties is positioned at regular horizontal centres. Extra wall ties should be positioned at jambs for all openings. The next course of blockwork should then be installed to secure the ties.

After raising each section of the inner leaf and before installing the insulation board, excess mortar should be removed, and mortar droppings cleaned from exposed edges of the installed insulation boards.

Step 2:

The first row of insulation boards should now be installed between the two rows of wall ties (fleece must face outwards to cavity), ensure each insulation board is retained tight against the inner leaf and joints are butted.

Secure each board at a minimum of three points. Additional ties may also be required to satisfy structural requirements or to ensure adequate retention of the boards or cut pieces.

Step 3:

Apply a self-adhesive breathable tape to all horizontal and vertical joints, board edges and abutting junction interfaces. (no less than 100mm wide and no less than 50mm either side of any edge. Additional layers may be applied.)

These surfaces should be clean, dry and free from grease, dust, and dirt prior to application. Next, build the outer leaf to the level of the top of the boards and repeat the process. (Cavity of 10mm or less).

If finishing at a gable, insulation boards should be continued 200mm beyond the height of the toper storey ceiling and a cavity tray installed above the insulation