Modelling the cooling energy saving potential of facade greening in summer for a set of building typologies in mid-latitudes

Abstract Densely populated city quarters lacking green increase the urban heat island effect and thermal discomfort outdoors and indoors. Facade greenings (FG) cool buildings and their surroundings through shading, insulation and transpiration, as demonstrated experimentally. FG also reduces energy consumption for building cooling. Because of complex interrelationships, to assess the performance of FG towards different buildings is not trivial. Therefore, a validated numerical heat-mass transfer model is proposed and applied to describe the energy saving potential of a one-layered FG for nine wall compositions representing relevant building types, climatic conditions in Berlin, Germany and Ljubljana, Slovenia and the south- and westward exposition. The buildings represent several functions and a range of wall insulation levels. For each scenario, temperatures and energy in- and outflows are calculated from June to September (20-year average). FG can reduce exterior and interior wall temperatures by up to 17 K and 2.9 K, respectively. For the whole period, energy savings range from 2 to 16 kW h  m -2 depending on building and climate. Results show that both, level of insulation, thermal inertia, exposition and climatic conditions must be considered when predicting FG’s energy saving potential for buildings. The introduced model can be used to predict cooling performances and to identify priority zones for FG implementation in cities.