Abstract: In the case of an out-dated building, replacing poorly sealed windows and doors results in significant energy savings, but it is essential to consider the building's structural principles during the modernization process.This study underscores the critical importance of both high-performance window systems and high-quality installation practices in achieving optimal energy performance in residential building renovations. Proper air sealing and the integration of effective shading devices, including roller shutter systems, have been shown to significantly reduce both heating and cooling energy demands, leading to substantial energy savings. These findings emphasize that both material selection and precise installation are essential for maximizing energy efficiency in residential retrofits.