There is no doubt that there has been a significant promotion of energy efficiency in buildings in the European Union since the adoption of the Energy Performance of Buildings Directive in 2002 (Jansen , 2005). This trend towards energy-efficient buildings has started to be prominent lately in Greece. However, there has been a shift in the direction of scientific research relating to the energy and environmental performance of buildings towards a focus on occupant comfort and the perception of a building's performance (Steemers and Manchanda, 2010). This study attempts to fill a gap in knowledge regarding office building design in relation to user experience and building performance in Greece. The recognition of climate change by scientists, politicians and the general public as a major challenge has led to the adoption of conservation measures of all resources, energy, water and materials, as well as encouraging sustainable development and conservation practices. construction. Within the definition of sustainable development, which requires that “development meets the needs of the present without compromising the needs of future generations” (WCED, 1987), buildings have an important potential role. Because they are made from long-lasting, energy-intensive materials and are passed down to future generations, if they do not meet the needs of the future, they cannot be considered sustainable. Furthermore, they are responsible for a large part of the consumption of natural resources and consequently greenhouse gas emissions (Fisk, 2001). In the context of sustainable development, buildings have started to be seen as positive and important capital assets for actualizing organizational goals and smooth functioning. being. How to manage...... half of the paper......y the efficiency of each building to be evaluated and force landowners to show the energy rating certificate before selling or renting a building (CRES, 2009) . This certificate would simply report the annual energy consumption of a building and therefore the annual quantity of CO2 it produces. These standards will replace the legislation on the thermal requirements of buildings implemented in 1979, which indirectly refers to the energy performance of buildings by making it mandatory to apply thermal insulation in all new buildings, but without taking into account solar gains or any other source of heat inputs (Papadopoulou, 2009). This change is illustrated in Figure 1.3. The new regulations also affect existing buildings that will be renovated, which is very important as only a small percentage of new buildings replace the country's old building stock each year.