School of the future: Deep renovation of the Solitude-Gymnasium in Stuttgart

The energy efficient renovation of the Solitude-Gymnasium in Stuttgart is one of the 4 demonstration buildings within the EU 7FP project "School of the Future". The secondary school with about 710 pupils consists of a typical configuration with a main building, a building of scientific classes, a big pavilion, a small pavilion and a gym, built between 1966 and 1975. The main building and the gym include flats for the caretakers. The total heated floor area of the buildings amounts to 8,924 m². The exterior walls of the buildings are made of exposed concrete or brick. All buildings have flat concrete roofs that had no sufficient insulation before the retrofit. Most windows consisted of PVC-frames and double-glazing, but in some corridors and stairways single-glazed facades existed. The heating was generated centrally for all 4 buildings by two gas boilers that replaced an earlier system in 2004. Domestic hot water for the gym is generated by a heat exchanger based on the heating water. Ventilation systems without heat recovery existed for some indoor rooms, some rooms in the building of scientific classes and the gym. All 4 demonstration buildings in the School of the Future project have the same goals: - Reduction of the total energy use > factor 3, verified through monitoring - Reduction of the heating energy use > 75 %, verified through monitoring - Improvement of the indoor environment quality (air, daylight, acoustic, thermal comfort) with impact on the pupils' performance, analysed by short-term measurements and questionnaires The building envelope renovation measures at the school in Stuttgart included external thermal insulation systems and curtain wall facades with 14-18 cm polystyrene insulation, 16-22 cm of expanded polystyrene on the roofs and mostly triple-glazed windows. The new heating system is a co-generation plant in combination with the existing boilers. The ventilation of the classrooms is now realised by decentralised ventilation units with 80% heat recovery (main building) or by hybrid ventilation consisting of window opening supported by actuators at the upper part of the windows that are controlled by timers and manually by the teachers. CO2 visualisation systems show the teacher when window opening is necessary. The existing ventilation system in the building of scientific classes are improved by central heat recoveries of 80% - 90% efficiency. Also the lighting system was updated by T5 compact fluorescent lamps, electronic ballasts, daylight control and presence detectors. A one-year monitoring period will show whether the energy performance goals (reduction of final energy from 225 to 58 kWh/m²yr and primary energy from 215 to 54 kWh/m²yr) and the indoor comfort goals can be achieved