... based on fabulous marketing?
SupaWall® panels are extremely thermally efficient and have been tested by the National Physical Laboratory who confirmed a U-value of 0.12 W/m2K. When typical cladding is taken into account the U-Value is 0.11 W/m2K
As an option, the 50mm polyurethane insulation on the cavity face of the timber frame can be omitted, giving U values with and without cladding of 0.17 W/m2K & 0.18 W/m2K respectively.
We have calculated this wall construction several times; the best we come up with is an overall U value of 0.17W/m²K which is describing the best case scenario; the mentioned "typical cladding" is typically vented, so it does not really improve the U-value but rules the humidity level between the two walls which seems to make the dew point critical. Also, as the stone cladding needs to be attached to the wood construction, usually by stainless steel pins, the thermal bridging effect would further strain any U-value calculation, the correct one or its phantasy's version.
So what makes it 0.12? What did we miss?