The thesis deals with energy intensity of a low energy office building. In the thesis, em-phasis is put especially on the calculation of energy consumption for heating (cooling). The energy intensity of the building is determined and evaluated by four methods of calculation, which are compared with a valid certificate of energy performance of the building, which arose at the time of its construction. In the experimental part of the the-sis, the energy intensity of the building is compared to the actual energy consumption obtained by two experimental measurements in heating season 2012/2013. (The building is operating partly only). Different methods of solutions and valid legal regulations are elaborated in detail in the first part of the th...