It is generally accepted that climate changes will have a major effect on our lives. However, buildings will also be faced with climate changes, and these changes will have an impact on indoor comfort, energy demands and the efficiency of building services, especially on those supporting free cooling and free heating. In order to predict the expected changes in a building's thermal response during its lifetime, it is necessary to look at the climate changes predicted for the future. In our study, the climate changes were considered by using simplified mathematical models combined with available test reference years to establish 'corrected test reference years'. A transient simulation tool, TRNSYS, was used to simulate the indoor climate and the useful energy demand for the heating and cooling of different buildings with different free-cooling techniques. In order to predict the expected changes in a building's thermal response, the meterological parameters for the moderate, continental climate region of Slovenia were taken into account. The study shows that during a building's lifetime, significant changes in useful energy demands can be expected-a decrease in the useful energy demand for heating of between 23 and 40% and an up-to-38-times increase in the useful energy needed for mechanical cooling. In buildings without mechanical cooling, the efficiency of the different free-cooling techniques should be increased by between 100 and 200% to ensure the same living comfort. The results presented in the study confirm that it is necessary to evaluate the consequences of global climate changes from the point to view of energy use in buildings, their contruction and the buildings' service installations. Copyright (C) 2008 John Wiley & Sons, Ltd.