The objective of this thesis was to offer a plan for reconstrucion of semi-detached house, which does not correspond with modern-day standards of energetic efficiency. Firstly, the building had to be measured and documented properly. A complete reconstrucion was part of the solution, as it is expected for the building to be torn down entirely to the level of foundation slab. The broad issue is to design the connection of the new construction onto the neighbor's external wall of semi-detached house as well as design of geometry, disposition while maintaining higher thermal performance standard. The design also reviews and explains the choice of most suitable construction system for the concept of the new structure. Critical details, which are part of the construction and hold thermal bridges needed to be analyzed thoroughly via outputs of several softwares. To display the energetic performance, a complex calculation for the specific heat requirement was needed aswell. The evaluation of entire thesis is the comparison of house's energetic efficiency results from both before and after reconstrucion.