Nature-based solutions (NbS) are crucial for creating more resilient and sustainably developed build environments. These solutions use natural processes and ecosystems to address urban challenges, such as climate change, biodiversity loss, water and air pollution, and the urban heat island effect. Green walls are a nature-based solution that can be integrated into buildings to enhance thermal and acoustic performance. They also play a key role in carbon sequestration, acting as a carbon-negative element that helps reduce greenhouse gas emissions. By incorporating greenery into urban structures, green walls not only improve environmental sustainability but also contribute to healthier, more energy-efficient buildings. Recent studies highlight the positive psychological effects of exposure to green spaces, showing they provide a restorative impact in teaching environments. As a result, these greening solutions not only enhance environmental comfort but also promote the well-being of building occupants. In this study the application of various passive design solutions, including a green wall, is tested to evaluate its effect on environmental comfort conditions of an educational building located at an University in Lisbon. Also, an optimal cost methodology will provide an informed decision on the most cost-effective rehabilitation strategies that improve the building's energy efficiency and promote a resilient building envelope to climate change conditions.