A systematic calculation of the time constant tau is presented for Greek buildings. This type of information is not available for many other countries. Correlations are developed which provide values of tau for eight general classes and 21 types of buildings with 15 and 10 kinds of walls and roof constructions, respectively. The total floor areas of buildings range from 30 to 3000 m(2). Only infiltration heat-losses were taken into account in the calculations of time constants, but any level of ventilation can be included by making appropriate corrections. Examples illustrate how the time constants are related to the thermal response of the buildings.