The Example of the “Green Class” Project in Krakow: A New, Mobile System of Educational Facilities That Takes Rainwater Retention into Account

Educational institutions in Poland often struggle with various problems, such as the lack of an adequate number of rooms or the poor technical condition of buildings. This is due to many factors, such as the age of the buildings, demographic trends, migration, political, social, historical, and cultural conditions and, above all, financial conditions. In order to address these problems, the Krakow University of Technology undertook the implementation of the “Green Classroom” scientific project as part of the “Science for Society” programme of the Ministry of Education and Science. The Green Classroom is a mobile, free-standing educational facility consisting of a geometric arrangement of four basic modules. Integrating this type of facility into existing infrastructure, especially in urban areas, requires the availability of suitable land, taking into account hydro-meteorological and wastewater conditions. This study presents a method using geographic information system (GIS) tools to select school areas where it is possible to locate “Green Classrooms”, taking into account sustainable land retention. Based on typical rainfall for the city of Krakow, stormwater runoff was calculated taking into account the adopted “Green Classroom” module. An additional sealed surface (a “Green Classroom” system) increases the rainwater runoff by approximately 1 m 3 . In order to balance the rainwater runoff, it is recommended to install a rainwater collection tank with a capacity of 1 m 3 next to the “Green Classroom” module. In order to relieve the storm sewer system, especially in highly sealed urban areas, it is recommended to use aboveground or underground stormwater tanks. The size of the tanks should depend on the impervious surfaces and their number on the site conditions. Nomograms for the city of Krakow have been developed to estimate the size of tanks.