The Effect of the U Value in the Energy Performance of Residential Buildings in Greece


  • Dimitrios Bikas Aristotle University of Thessaloniki
  • Panagiotis Chastas Aristotle University of Thessaloniki



nearly zero energy building, residential buildings, energy consumption, U value, opaque building elements


According to the European 2012/31/EE Directive all new buildings until 31/12/2020 and all new buildings occupied by public authorities until 31/12/2018 should be buildings with nearly zero energy consumption. Many countries of the European Union have established legislation with provisions for the energy performance of the buildings with a further goal to reach the nearly zero energy consumption building. In Greece there is a presence of this attempt from the year 2010 with the Regulation of the Energy Performance in Buildings (ΚΕΝΑΚ, 2010). This was a first attempt for upgrading the energy performance and for establishing the energy inspection of buildings and the relative provisions. In order to achieve the goal and fulfill the requirements of the European legislation a further attempt should be focused in interventions such as lower U value limits in the opaque building elements of the building envelope and windows, in upgrading the energy efficiency of HVAC systems and even the use of renewable sources to cover a percentage of the energy requirements of the buildings. This study aims to evaluate the effect of the reduction of the U value of the opaque building elements in the energy requirements and consumption in residential buildings in Greece, according the climatic zone that is located, as a step closer to the nearly zero energy consumption building.


Author Biographies

Dimitrios Bikas, Aristotle University of Thessaloniki

Professor, Director Laboratory of Building Construction and Building Physics, Vice chairman of the Dept. of  Civil Engineering


Panagiotis Chastas, Aristotle University of Thessaloniki

Civil engineer and MSc “Environmental protection and sustainable development” graduate,, Dept. of Civil Engineering, Laboratory of Building Construction and Building Physics