The city of Flensburg plans to eliminate energy deficiencies at the schools of Fridtjof-Nansen-Schule, Fördegymnasium, Altes Gymnasium. The sports hall of the Fridtjof-Nansen School as well as the sports hall of the Fördegymnasium are optimised energetically with regard to the lighting systems. This is implemented by means of presence and brightness sensors in conjunction with modern LED sports hall lighting. In addition, the hot water treatment is being refurbished energetically at the mentioned locations. The existing storage charging system is replaced by a water flow system (synonym fresh water station). As a further measure, the upper floor ceiling in the east wing of the Gymnasium is insulated in the Old Gymnasium of the city of Flensburg.