In the present paper, an attempt has been made to estimate the energy consumption in Greek buildings. This is a subject of great interest due to the upcoming building certification that will take place in Greece after the application of the European directive concerning the energy performance of buildings. Our purpose is to examine the energy consumption throughout Greece by simulating the thermal behaviour of typical buildings. In order to achieve this we are founded on the philosophy of the computer programme EnerWin. Information with sketches of buildings showing the thermal zones, Greek climatic data, properties of the various construction assemblies, type of heating and cooling systems, the occupancy of the building in question, as well as hot water, lighting and ventilation profiles are fully outlined in the code. The annual energy needs of a Greek residential and an office building, as well as the breakdown of energy use are presented. The results of such a simulation can give us a first indication on which end uses are the most energy consuming, the "weaknesses" of a building and thus urge the owner or engineer to take conservation energy measures. The article focuses on the thermal comfort conditions of the occupants. Thermal comfort is an important issue which should not be overlooked. In the present article we will attempt to examine whether comfort conditions in typical Greek buildings comply with international standards and discuss the particularities of Greek people as far as thermal comfort, energy use and behaviour is concerned.