GreenPlusSchool@urban - Highly efficient facade and roof greening in combination with PV; optimal solution for energy efficiency in overall environmental consideration

In this project multifunctional façade - and roof constructions were investigated. Therefore, an old school building in an urban surrounding was greened. The building is made out of solid bricks. It was greened on selected parts of the façade and the roof. On some of the greened building parts, also photovoltaic systems were installed. The greening happened in a participatory process together with pupils and teachers. Also the monitoring, the researching and the maintenance were integrated into lessons by the teachers.

The greening systems were investigated concerning their ecological and economical features. The whole life cycle was considered for the investigations. In addition, the suitability of the different components from the greening systems was studied.

The project team found out that the thickness of the vegetation-support affects the resilience of the system. The thicker the vegetation support is, the more resilient is the system. Water shortage and extreme temperatures can be buffered better. Horizontal systems have a more homogeneous distribution of water because gravity has less impact than at vertical systems. The accessibility of the greening and its control units is important. The higher the accessibility, the more often the systems are maintained. It is important that the controlling systems are as simple as possible. The inhibitions to install a timer are lower than to program an irrigation system. Mechanical timers are the most easy to install. Online systems can send error messages and improve the reaction time of emergency maintenance activities. In general, the inhibition level to intervene into the system is higher, the more complex the technical system is. Suitable plants to work together with children are vegetative plant genera and species, such as: spider plant, bowstring hemp, ivy tute, philodendron, Virginia spiderwort and ludisia discolor.

Within this project it was found out, that the measured U-value is reduced because of the façade greening. The reduction depends on the ventilation openings and the size of the greening area. On uninsulated buildings an improvement of about 20% is possible. The indoor greening increases the hydrothermal comfortability. In the investigated greened classroom, the hydrothermal conditions were comfortable 73 % more often than in the not greened classroom during the winter because of the increased air humidity. Even though the air humidity was increased, there was no increase of mould spores. In the greened classroom the concentration of the mould spores was below or at the same level of other classrooms or the air outside. The concentration of dust was investigated for the sizes PM1, PM2,5 PM4 and PM10. In the greened rooms the concentration of the dust was below the concentration of the not greened rooms. This is true for all the investigated sizes. The CO2 concentration in the rooms is reduced because of the indoor greening. The reduction is small and has no relevant effect during the lessons in school. The greening systems increase the sound absorption coefficient of the rooms, which reduces the reverberation time. The reduction of the reverberation time depends on the type of the greening system. The combination of photovoltaics and greening leads to lower temperatures of the photovoltaic modules during hot days. The lower temperature of the modules increase the efficiency of photovoltaic. The biggest obstacle of this technology is the maintenance of the greening system. By measuring inlet and outlet of the amount of water the energy of evapotranspiration was calculated. On hot summer days a greened façade is able to cool its surrounding by up to 2 kWh/m² and day.