Rct

15:27 Sep 12, 2017 

You do not need to "translate" the "ct," because it is a subscript that is (edit) part of the symbol of a property. Therefore, Rsub(ct) = résistance thermique = thermal resistance. See reference: http://www.jeffjournal.org/papers/Volume7/7.3.10F.Rombaldoni...
Note: Another property of interest is Rsub(et) = water-vapour resistance. https://www.iso.org/standard/19081.html
https://www.researchgate.net/publication/277152749_Combat_In...

12:53 Sep 12, 2017 

Sorry, it looks like my question did not appear as intended. I had added the following : : Résistance thermique Rct
• 0,06 =<Rct<0,12 Classe 1
• 0,12 =<Rct<0,18 Classe 2
• 0,18 =<Rct<0,25 Classe 3

I know that "Rct" is just the symbol for résistance thermique, as ISO.org points out:
Rct
différence de température entre les deux faces de la matière, divisée par le flux de chaleur par unité de surface dans la direction du gradient

But I can't work out what the "ct" stands for (conductivité thermique??) and how to convey the whole thing in English. I have come across "R-value" but not sure if this is the correct translation.

Now that I have three different answers, I am not sure which one is right!

Thanks to all.