The heatwaves that have affected our civilization in recent years pose a serious threat to the environment as well as the proper functioning of our bodies. Schools are facilities with specific microclimatic requirements. Thermal conditions in educational buildings are decisive for the stimulation and efficiency of the learning process, as well as the interaction of students. Based on the measurements of thermal comfort carried out in the school building, with the energy standard of a passive building, it can be observed that in schools with very low energy consumption, the problem of interior overheating may occur in the summer months. In this paper, an attempt was made to search for alternative passive measures allowing for the required indoor microclimate conditions to be obtained. Such solutions are in line with the spirit of the European energy policy and sustainable development. A model of the school under study was created using the Design Builder simulation program. The role of mechanical ventilation and the possibility of night ventilation in reducing discomfort were examined. Consideration was given to the justification of using expensive heat pump installations with a ground heat exchanger to reduce overheating in summer. The application of the adaptive approach to the assessment of thermal conditions and the acceptance of limited overheating periods led to the conclusion that the analyzed building could function successfully without these additional installation elements. A proprietary tool for the analysis of microclimate conditions was proposed to estimate the hours of discomfort in a way that is objective and easy to calculate.