New Regulations on energy efficiency in buildings in the Republic of Serbia legislate values for the temperature correction factor used to calculate the heat flux to the outdoor environment through construction elements of a certain type. The temperature correction factor is used to correct errors caused by calculation of heat losses based on the design outdoor and indoor temperature difference of building elements adjacent to unheated spaces which are in direct contact with the ground or external environment. Since the temperature correction factor directly influences the calculation of total heat losses and total annual energy demand, it is recommended that the temperature correction factor be determined on the basis of measured values of outdoor and indoor air temperature, or, on the basis of the values obtained by the simulation. This paper presents the results of measurements in the High School of Design, Textile and Management in Belgrade in order to assess energy efficiency and the energy performance of buildings. Data obtained on the basis of measurements, such as indoor and outdoor temperatures, are used for the calculation of the heat transfer coefficient for the building envelope elements as well as to calculate a temperature correction factor for the unheated attic space of the building. This paper also offers a dynamic simulation of the multi-zones building in the TRNSYS environment. The aim was to compare temperature correction factor values obtained from measured temperature values, with those calculated from standard, taken from the Regulation table and produced by simulation.