With global concern about climate change on the rise, environmental certification of buildings with BREEAM Nor will provide a holistic evaluation on the sustainability of buildings, especially in Norway. When it comes to optimizing energy performance and indoor climate, a paradox often exists. This paradox becomes even more challenging in the context of educational buildings, where it can be difficult to achieve both optimal indoor climate and passive house standards due to potential negative impacts on energy performance, particularly with regard to energy use for cooling. In this study, energy performance and indoor climate are assessed in a pilot project (the school project: one of Norway’s most environmentally friendly schools). The connection between energy supply solutions, building envelope, and technical details will be elucidated. The study underscores the importance of post-occupancy evaluation to compare a building’s projected performance with its actual outcomes. This process helps identify gaps and discrepancies, allowing for adjustments to meet intended energy efficiency and environmental goals. This paper is partly based on a bachelor’s project by three bachelor’s students from Oslo Metropolitan University.