The present investigation focuses on the study of the thermal inertia of buildings examining the extent to which the envelope and internal components can moderate their internal climate. Especial emphasis is given to the analysis of thermal mass effects in conditions of overheating in buildings with predominantly day-time occupancy schedules such as offices and mixed use buildings. The thesis comprises three parts. The first part discusses the principles and definitions of thermal inertia identifying a number of aspects which are relevant to the thermal performance of buildings. A review of the physical principles and parameters for quantification of heat storage in building elements is also included. The second part presents the results obtained from a series of field experiments carried out in six buildings in different locations to observe the thermal reaction on their internal spaces according to the particular thermal mass characteristics of each case. The third part is devoted to the analytic work by means of parametric studies and by comparing the field experiments findings with computer simulation results and exploring additional aspects of thermal mass effects. The analytic studies included the application of the diurnal heat capacity method for the calculation of internal temperature swings obtaining results in close agreement with both SERI-RES simulations and field measurements. A calculation worksheet is proposed to facilitate the internal swing calculations. Finally, the conclusions obtained from the results were used to define a series design measures aimed at the improvement of indoor thermal conditions by the optimisation of the effect of thermal mass of buildings in warm environments.