Nowadays large transparent surfaces are widely used in office and public buildings. The positive effect of great views and natural light on people’s comfort is well known, but the high glazed ratio of building facades can lead to excessively high cooling energy demands. The heat load can be reduced by using glazing with high reflexion coating outwards and low emission coating inwards, triple panes and inert gas between the panes. Choosing proper thermal mass can further help in reducing the amplitude of the indoor operative temperature. In this paper the effects of solar factor of glazing, heat transfer coefficient of windows, windows area and thermal mass were analysed in an imaginary room with 3.0×4.0×2.8 m dimensions. As the results show the effect of the overall heat transfer coefficient is negligible. The effect of solar factor depends on the orientation. The expected differences between the amplitudes of the operative temperature are between 0.5 to 6 K for the analyzed room, depending on the thermal mass, orientation, solar factor and window area.