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Celotex CW4000

Celotex CW4000 is an insulation board aimed specifically at partial fill cavity wall applications to help provide the building with excellent quality of insulation. With low emissivity foil facings, CW4000 is manufactured from a rigid polyisocyanurate (PIR) Insulation Board that is suitable for use in extensions and new builds. CW4000 uses a blend of blowing agents that have zero ozone depletion potential (zero ODP) and low global warming potential (GWP) and reliable energy savings that are long-lasting for all buildings.

Celotex Cavity Wall Insulation Boards

Celotex CW4100 100mm Cavity Wall Board (1200mm x 450mm) – 3.24m2 pack

£46.64 ex VAT
Celotex Cavity Wall Insulation Boards

Celotex CW4075 75mm Cavity Wall Insulation Board (1200mm x 450mm) – 4.32m2 pack

£47.25 ex VAT
Celotex Cavity Wall Insulation Boards

Celotex CW4050 50mm Cavity Wall Board (1200mm x 450mm) – 5.94m2 pack

£45.57 ex VAT
Celotex Cavity Wall Insulation Boards

Celotex CW4085 85mm Cavity Wall Board (1200mm x 450mm) – 3.78m2 pack

£63.79 ex VAT

Celotex CW4000 qualities:

  • Excellent Thermal Performance
  • Available thickness from 40mm – 100mm
  • Squared Edges
  • enhanced features deliver thinner solutions that meet target U-values
  • High-performance facer
  • Provides a level of sounds proofing

With Celotex CW4000 you are specifying an insulation board that is easy to fit between wall ties using cavity tie clips for retention and comes in conveniently sized boards for installation between cavity wall ties. This product includes low emissivity foil facings giving improved thermal insulation performance within cavity air spaces. Celotex Cavity Wall Insulation provides excellent dimensional stability and is easy to transport as well as handle and install.

If you’re looking for something similar to Celotex Cavity Boards, Thermawall TW50 PIR Cavity Wall Insulation can be a great alternative.

Celotex Cavity Wall Insulation Boards


  • Euroclass E Reaction to Fire classification, according to BS EN 13501-1
  • A+ rating in comparison to the BRE Green Guide 2008
  • CE marking complying with BS EN 13165:2001
  • CFC/HCFC free
  • in accordance with BS EN ISO 9001:2000 and quality management systems by Celotex Limited

More Information:

  • Thermal conductivity: 0.022W/mK
  • Area/pack: 5.94m2
  • Board weight: 2.48kg
  • R-Value: 2.25m2 K/W
  • Compressive strength: 120kPa
  • Water vapour resistance: Greater than 150MNs/g
  • Dimensional stability: DS (TH) 8

Available in sizes:

  • Dimensions 1200 × 450 mm
  • Thickness 40mm, 50mm, 60mm, 75mm, 85mm, 100mm
  • Thickness 50mm


Stocked Thickness40mm50mm60mm75mm85mm100mm
Lambda Value (W/m.K)0.0220.0220.0220.0220.0220.022
R-Value (m2.k/W)1.802.252.703.403.854.50
Length (mm)450450450450450450
Width (mm)120012001200120012001200
Maximum Weight (kg/m2)1.411.922.262.783.133.65
Pieces per Pallet22417616012811296

Celotex CW4000 Installation Guide

CW4000 is Celotex Cavity wall insulation which is made to be fitted in between the breeze blocks structure of the building (inner leaf) and the outside brickwork (outer leaf) to help insulate the building. The Celotex Cavity wall insulation must be fitted as you go when laying the inner and outer leaf.

Step 1:
Install wall ties into the inner leaf at 600mm apart 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 cavity tie clips (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 in place.

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 the cavity), ensure each insulation board is retained tight against the inner leaf and joints are butted to get the best quality of insulation.

Secure each board at a minimum of three points. Additional ties may also be required to satisfy structural requirements such as around window frames or doors or to ensure adequate retention of the Cavity Wallboards or cut pieces.

Step 3:

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

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

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