Online Insulation U-value Calculator

The Celotex insulation U-value Calculator gives you instant access to calculating your required insulation thickness and product solution.

U-value Calculator
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IMPORTANT: On 1 September 2017, Celotex took the precautionary measure to temporarily suspend the supply of Celotex FR5000, Celotex CG5000, Celotex CF5000 and Celotex SL5000 while we investigate the results of recent tests (Parts 6 and 7 of British Standard 476). In addition, we have recently identified a compliance issue relating to our calculation and testing of the declared lambda value of products in the 4000 and 5000 ranges and the Crown-Bond and Crown-Fix products within the Crown Flat Roofing range. Due to this issue, the suspension of the 5000 range will continue and now includes the FI5000 and GD5000 products. Materials relating to the 5000 range products are for information only.  Please note that all products in the TB4000, GA4000 below 100mm, PL4000 and CW4000 ranges manufactured after 15 December 2017 will be marketed from January as Celotex 3000 with a declared lambda value of 0.023 W/mK.

Please use the link below to read our full statements regarding declared lambda:

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Please use the link below to read our latest statement regarding Class 0:

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The professional Celotex U-value Calculator is one of the most comprehensive online calculation services in the industry, with a variety of different insulation applications covered.

Specify your desired U-value before immediately calculating the required insulation thickness and project.

"I use the Members Area of the Celotex website on a daily basis. In particular I use the U-value Calculator within the Members Area because I can quickly produce U-value calculations for inclusion within my projects' specification" - Robin Bradbury of Bradbury Design

"Thank you for the online U-value calculator, it is really easy to use. I plan to specify Celotex from now on. It's more commonly available and easier all-round" - Jon Gay, architect from Lochaber

In order to access the Celotex U-value Calculator and download your calculation PDFs, you must register for the Members Area, which is quick and easy!

How to access and use the Celotex U-value Calculator

The following video explains how to access and step through using the online U-value calculator. 


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Why register?

Our U-value calculator app is also available from the App Store.

If you require further help or advice on an already created U-value calculation and would like to speak with an advisor, please contact our Celotex Technical Centre on 01473 820850.

Lines are open Monday – Friday, from 8.00am – 5.15pm.

Please note, some products in the U-value calculator may not be available from stock and subject to minimum order quantities and extended lead times.