The problem of reducing primary energy consumption is increasingly discussed in the technical literature. Relatively large amounts of energy are used to heat rooms. In the case of resources of much cheaper waste energy or energy from renewable sources with a temperature lower than required in the rooms, the so-called "thermal barrier" placed in external walls can be used to reduce heat transmission losses. The thermal barrier is a vertical wall element with pipes with a heating medium installed in the partition, with a temperature lower than the temperature in the room but higher than that resulting from the heat transfer through the partition without a barrier. In the paper, on the basis of the developed model of a partition with the thermal barrier, for the assumed input values and the partition's surroundings, the efficiency of the thermal barrier was defined and determined. A formula for its efficiency was derived. The efficiency of the thermal barrier does not depend on the temperatures of the barrier base and the wall environment, but only on the geometrical and thermodynamic parameters of the partition. It has also been shown that the efficiency of the thermal barrier is the highest when the resistance of the partition on both sides of the barrier is the same. Knowledge of the barrier efficiency will allow to easily determine the average barrier temperature and the amount of heat given off by the room and by the heating medium flowing in the barrier. It should be noted that the total amount of heat given off by a wall with a thermal barrier is greater than through a wall without a barrier, but the costs of heating the room may be lower.