The article explores the object that has 2 stages of construction. Projected houses are identical in heat engineering characteristics and design features. The building is the first phase of construction was built on the minimum requirements for thermal protection. When the first house was built, it was decided to correct the project of the second stage. Project change was due to the increase in the requirements for the thermal protection of the building. The second building is built on the highest standards of insulation and energy saving. The research is to calculate the annual heat energy consumption for heating buildings in the cold and transitional periods of the year before the adjustment of the project and comparing these values with the regulations. It is also in the process of calculating the defined thermal performance building envelopes. The purpose of research is to justify the need to adjust the project to improve energy efficiency.