A method for arranging an accumulating device in proximity of a floor of a vehicle forming a bottom wall of a passenger compartment of the vehicle itself; the accumulating device has a heating base wall which is free from heat insulation, and a non-heating base wall which is parallel and opposite to the heating base wall and is provided with a heat-insulating material layer; and the method provides for the steps of arranging the accumulating device in a seating obtained in proximity of the floor; and implementing the accumulating device with a symmetry allowing the reversal of the accumulating device itself within the seating obtained in proximity of the floor in such a way that the heating base wall may be equally either facing upwards and then towards the passenger compartment or facing downwards and then towards the external environment.