The implementation of the European Directive on the Energy Performance of Buildings (EPBD) is a milestone towards the improvement of energy efficiency in the building sector. However, even in cases where impressive measures can be implemented in the densely built urban environment, the less glamorous measure of building's envelope thermal insulation remains a prerequisite towards the improvement of the building's energy efficiency. Despite the insulation requirements specified by national regulations, thermal bridges in the building's envelope remain a weak spot in the constructions. Moreover, in many countries construction practices tend to implement only partially the insulation measures foreseen by regulations. As a result, thermal losses are in practice greater than those predicted during the design stage. This paper presents a study on representative wall thermal insulation configurations used in Greek buildings, in order to investigate the impact of the thermal bridges on the energy consumption. The double wall construction, used widely in Greece and not only there, is rather susceptible to the occurrence of thermal bridges, in contrast to a typical thermal insulating facade, like the one applied in Central Europe. The analysis of the thermal bridges' impact will in that sense also highlight the potential for energy renovation measures in older buildings. (C) 2008 Elsevier B.V. All rights reserved.