The paper consists of a theoretical and a practical part. In the theoretical part, an overview of the conditions that construction should fulfill from the aspect of energy efficiency is given. In the practical part, an assessment of the condition of the "Auto-transport" office building and a calculation of the required energy for heating for the existing condition with a proposal for appropriate measures were made. After that, the calculation of the required energy for heating after the intended iprovement measures was made, all in accordance with the national Rulebook on the energy efficiency of buildings.