The aim of the thesis is the design of the energy passive flat building in functional concept of modern wooden construction. The introduction of the theoretical part presents recent information about current wooden construction systems it also includes information about CLT construction system which was chosen as a bearing system. Theoretical part analyzes the procedure of thermal-technical assessment and the requirements and processes that were followed. The main part of the thesis consists of technical drawing and the concept of the designed object which was subsequently analyzed according to the requirements of STN 73 0540. In closing part the reports of building heat regulations, space heating losses and heating losses of single flats (PHPP) were calculated and analysis of critical details was conducted.