I've written to B&Q:
Looking at Thermawrap General Purpose Wrap on your website, it says: Thermal resistance 1.455m²k/w in Wall Lining installation. Since its thickness is quoted as 4mm, this would give a thermal conductivity of ~ 0.00275 W/mK. Expanded polystyrene has a thermal conductivity of 0.033 W/mk, so are you saying that Thermawrap is a ~12 times better insulator than polystyrene?
I'll let you know if it's really true!

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