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Celotex XR4000 insulation board

The thickest high performance PIR insulation board for floors,walls and roof applications.

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What is Celotex XR4000?

XR4000 is a rigid polyisocyanurate (PIR) insulation board with high thermal performance. Available up to 200mm thick, low U-values can be achieved without doubling-up insulation layers. Celotex boards are lightweight and rigid; making them easy to handle, transport, and fit on site, and suitable for applications including:

Ground floors - whether solid concrete, block and beam, or suspended timber joist, and including where underfloor heating is used.

Timber and steel framed walls - between the studs.

Pitched roofs - between the rafters.

Flat roofs - in ventilated cold roof constructions, installed from inside the building.

● Other retrofit and refurbishment projects - lining existing timber and masonry structures to make them more thermally efficient.

As well as being CE-marked, Celotex XR4000 is certified by the British Board of Agrément for floors, framed walls and pitched roofs. With regard to floors, the BBA certification assessed thermal performance, condensation risk, floor loading and durability. Made at our original site in Hadleigh or our state-of-the-art facility in Eggborough (opened in 2018), you can be confident of it providing reliable, long-term energy savings that help to ‘future-proof’ your building.

How does XR4000 perform?

The entire thickness range offers a low thermal conductivity (lambda value) of 0.022 W/mK, putting XR4000 among the best-performing widely-available insulation materials on the market.

In any of its intended applications, XR4000 will help to provide most of the thermal insulation performance - but the overall heat loss from a building element depends on all of the materials used and the way they’re installed. Use our online and mobile U-value calculators to help you find the most efficient solution for each type of construction.

Product benefits

Celotex XR4000’s low emissivity aluminium foil facing can help achieve lower U-values when installed facing a clear air space within a construction. Check our frequently asked questions for common queries about positioning and installing products correctly, or contact our technical services team.

Like all Celotex products, XR4000 is a thermal insulation solution that can help to meet energy use and carbon dioxide emissions targets set by national building regulations.

  • Board size: 1200 x 2400mm
  • Thickness : 110-200mm
  • Lambda: 0.022 W/mK
  • Facer: Low emissivity composite aluminium foil
  • Manufactured using a blowing agent with zero ozone depletion potential (ODP) and low global warming potential (GWP).


1With regard to timber frame dwellings up to 18m in height, the BBA certification assessed thermal performance, condensation risk, water resistance and durability. With regard to pitched roofs, the BBA certification assessed thermal performance, condensation risk and durability.


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