Not yet a Jersey RdSAP Convention
In some older dwellings, DEAs might find vermiculite insulation within the loft. This is usually characterised as a gravel-like material filling between the joists of a loft space.
To model vermiculite insulation within RdSAP, the measured thickness of the insulation must be HALVED. This is because the thermal conductivity of the material is much worse than an equivalent thickness of wool-type insulation.