Celotex CW4000

Celotex CW4000 is an easy to install polyisocyanurate (PIR) insulation board with excellent thermal performance, featuring  a low emissivity foil facing. Available in thicknesses from 40mm to 100mm, it is suitable for use in partial fill cavity wall applications

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Product Features


  • Lightweight 1200 x 450mm boards
  • Squared edges
  • Low emissivity foil facing
  • BBA approved – certificate 16/5343 (Partial Fill Cavity Walls)


Fire Classification

Euroclass F Reaction to Fire classification, according to BS EN 13501-1. Products with this level of classification are not provided with a rating for smoke emission.

Product Specification

Thickness (mm) Length (mm) Width (mm) Lambda Value (W/m.K) R-Value (m².K/W)
40 450 1200 0.022 1.80
50 450 1200 0.022 2.25
60 450 1200 0.022 2.70
75 450 1200 0.022 3.40
85 450 1200 0.022 3.85
100 450 1200 0.022 4.50

Product Benefits


  • Thermal Performance - Excellent thermal performance with a thermal conductivity of 0.022 W/m.K, reducing the thickness of insulation required to hit the target U-value.
  • High Performance Facer - Low emissivity foil facing provides improved thermal performance in sealed cavity air spaces, improving the achievable U-value.
  • Easy to Install - The boards are light and rigid assisting with ease of transportation, handling and fitting. They are sized to fit standard wall tie spacing for ease of installation
  • BBA Certified - Celotex CW4000 has been assessed by the BBA as fit for use in defined partial fill cavity wall applications if installed, used and maintained as set out in the certificate. Please read the BBA certification page for full details and restrictions.


Key Considerations

When using Celotex CW4000, you need to satisfy yourself that use of the product meets all relevant national Building Regulations and guidance as well as local, national and other applicable standards relevant for your construction or application, including requirements in relation to fire and applicable height restrictions.
Please refer to the following product documents:

Celotex CW4000 should not be used in the external walls of buildings over 11 metres in height. Recent changes to Building Regulations mean that only non-combustible insulation or insulation of limited combustibility should be used in buildings of that height.