The Greek building stock is the most wasteful and every year the situation is getting worst. Comparison between the Mediterranean countries evinces that Greek households present the highest consumption. It is almost 30% higher than in Spain and about twice as in Portugal.Simultaneously, it is almost equal to that of cold Netherlands and significantly higher than in countries with a cooler climate such as Belgium and the Czech Republic.

At the same time, the regulations of our country were created after the war and were incorporated some decades after their creation. Furthermore, there is no control of the design and its proper adjustment at the site. The relevant regulations of European countries specify in significant detail what exactly an energy design must include, determine clear limitations of energy efficiency and control the success during the adjustmentof the design.

In Greece the energy saving is considered as a reduction in quality of life, as well there is an incorrect impression for the bioclimatic design. There are no standard solutions which can be applied to any building, neither the energy saving depends only on which heating and cooling system will be used. A properly designed building with an inefficient system can display lower consumption than the most efficient system in an unsuitable building.

The principle purpose of this study is to present and analyze the current situation with regard to the building stock of the country and to propose ways of upgrading. The study is comprised of three main parts.

The first part focuses on the energy balance and the impact of buildings on the environment, as well theGreekbuilding stock and its energy consumption are analyzed. There are presented the causes of poor energy behavior of theGreekbuilding stock and the evolution of energy efficiency of buildings, leading at the analysis of the existing legislation.

The second part is a presentation of proposals with interventions in old blocks of flats that aim at the reduction of energy consumption.

Conclusively, in the third part, by leveraging the knowledge from previous parts, a case study is presented. In an old block of flats in Athens are applied those who were proposed in the second part, aiming at its better energy function.