The main problems of the post-war block of flats in Hungary are the poor thermal performance: thermal bridges, bad whether proofness and air-tightness and the related fabric damages, resulting in high operational cost and low quality of living standard. Uncontrollable heating systems increase the waste of energy. Although several good initiative can be referred to in the past as well as recently, some refurbishment attempt which neglected the complexity of the system further increased the problem, sometimes making disputable the rationality of the applied measures. False, simplified calculation concepts of pay-back time slowed down the decision making and the allocation of funds for added thermal insulation. On the other hand successful demo projects proved the great energy saving potential and positive side effect of thermal rehabilitation.