The energy-efficient renovation of the Saint-Just Administrative Center aimes to improve the global energy performance of the buildings with the goal of 90 kWhef/m².year (absolute value by 2030 – 15%) in comparison to the buildings’ current energy consumption of : 146 kWhef/m².year. To achieve this goal, our solution is to propose an exterior thermal isolation by biosourced materials for the facades suffering from extreme summer heat, and those suffering from thermal loss in ther winter, to replace all the current windows and doors by double-glazed frames equiped with different heat-protection system. Our mission is also to instore an architectural harmony to all of the building’s facades in order to create a single architectural unity.