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Celotex TB4000

High performance PIR insulation for overcoming thermal bridging.

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What is Celotex TB4000?

The thinnest product manufactured by Celotex, TB4000 is a high performance, rigid polyisocyanurate (PIR) insulation board specifically designed to address thermal bridging and reduce localised heat losses.

It can be used throughout a building project to help maintain continuity of the insulation envelope, and is suited to floor, wall and roof systems. Specific applications include perimeter upstand insulation in ground floors and lining door and window reveals in retrofit projects.

As well as being CE-marked, Celotex TB4000 is certified by the British Board of Agrément for floors, framed walls and pitched roofs. Made at our original site in Hadleigh or our state-of-the-art facility in Eggborough (opened in 2018), it can help you achieve reliable, long-term energy savings.

How does TB4000 perform? The entire thickness range offers a low thermal conductivity (lambda value) of 0.022 W/mK, putting TB4000 among the best-performing widely-available insulation materials on the market.

TB4000 will contribute to the thermal performance of any element in which it is used - 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 TB4000’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, TB4000 is a thermal insulation solution that can that help to meet energy use and carbon dioxide emissions targets set by national building regulations.

  • Board size: 1200 x 2400mm
  • Thickness : 12-40mm
  • 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 floors, the BBA certification assessed thermal performance, condensation risk, floor loading and durability. With 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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