This paper starts with a reference to the energy efficiency of buildings, the buildings with almost zero energy consumption (nZEB - nearly Zero Energy Buildings) in Europe and Greece, the legislation on them and their relation to renewable energy sources. This is followed by a brief description of all renewable energy sources, their role in energy autonomy in the residential context and the situation in Greece in terms of its climate. Later it is explained how in recent years low-energy building design has turned to two aspects: one is active technologies, and the other is passive design strategies.  This is followed by some modern active technologies and systems. Then some examples of passive construction in Greece are mentioned. Finally, a concluding conclusion is made on all the above topics.