Method for determining a quantity representative of the thermal resistance ( U, R T, R) of a dividing wall between a first environment and a second environment, characterized in that it comprises steps in which: - over at least two successive time periods D k corresponding to distinct heating powers P k of the first environment, respectively to distinct temperatures applied in the first environment, there is undertaken a campaign of measurements of the heat flow rate through the wall q k and of the temperature in the first environment T 1 k, respectively of the power in the first environment, at closely spaced time intervals, as well as the determination of the temperature in the second environment T 2 k at closely spaced time intervals; - the value of the quantity representative of the thermal resistance ( U, R T, R) of the wall is determined by bringing into convergence: ∘ on the one hand, a thermal model expressing the temporal variation of the temperature, respectively the temporal variation of the power, in one environment divided off from another environment by a wall, as a function of the heat flow rate through the wall, of the temperature in the other environment and of physical parameters of the wall, on the basis of which the quantity representative of the thermal resistance of the wall is calculable, and ∘ on the other hand, the measured evolution of the temperature T 1 k ( t), respectively of the power, in the first environment as a function of time. - over at least two successive time periods D k corresponding to distinct heating powers P k of the first environment, respectively to distinct temperatures applied in the first environment, there is undertaken a campaign of measurements of the heat flow rate through the wall q k and of the temperature in the first environment T 1 k, respectively of the power in the first environment, at closely spaced time intervals, as well as the determination of the temperature in the second environment T 2 k at closely spaced time intervals; - the value of the quantity representative of the thermal resistance ( U, R T, R) of the wall is determined by bringing into convergence: ∘ on the one hand, a thermal model expressing the temporal variation of the temperature, respectively the temporal variation of the power, in one environment divided off from another environment by a wall, as a function of the heat flow rate through the wall, of the temperature in the other environment and of physical parameters of the wall, on the basis of which the quantity representative of the thermal resistance of the wall is calculable, and ∘ on the other hand, the measured evolution of the temperature T 1 k ( t), respectively of the power, in the first environment as a function of time. ∘ on the one hand, a thermal model expressing the temporal variation of the temperature, respectively the temporal variation of the power, in one environment divided off from another environment by a wall, as a function of the heat flow rate through the wall, of the temperature in the other environment and of physical parameters of the wall, on the basis of which the quantity representative of the thermal resistance of the wall is calculable, and ∘ on the other hand, the measured evolution of the temperature T 1 k ( t), respectively of the power, in the first environment as a function of time.