Many factors influence on the energy efficiency of each building. Among other things, the composition of the structural elements and their properties are the influencing factors of thermal response of the building envelope and building’s energy consumption. With calculation methods we can determine the thermal transmittance of the constructional element, although they simplify the real situation and represent »idealized« condition to some extent. With a purpose to evaluate the energy consumption of selected buildings in more realistic way, it is able to determine the thermal transmittance also with measuring device and its belonging in-situ measurement.
In this thesis we represent the comparison between the thermal transmittance of building envelopes, obtained by using the in-situ measurement and by using calculation methods. The comparison between those two methods was the source for evaluation of the existing difference of thermal transmittance. Based on this, we identified the potential impact of the energy efficiency in selected buildings of Ljubljana University. We found that the average difference of external walls is 44-percentage and the difference in roof measurements is 99-percentage. Consequently, there comes to the difference in calculation of required energy for building operation (in our case amounts ΔQT 15 = kWh/m2a). This highlights the fact that the thermal transmittance in considerable extent influences on energy consumption of the building.