Answer: it is a radiator that heats both the room immediately and the walls of a room in a sustainable way.
The soft heat radiator is a particular model, an improved version of the inertial radiator. It contains at least two resistances, a resistance which heats the front of the radiator to diffuse heat by radiation in an almost instantaneous way in the room, and a second resistance at the back which heats a refractory material like brick or ceramic to diffuse soft heat in a sustainable way. A soft heat radiator provides temperature quickly and radiates heat long after it has been turned off. The soft heat radiator is a fixed radiator, there is no mobile version. And the choice available commercially is rather standardized. In addition, its starting price is quite high. You too, send us your brico question