Green Façades in the Urban Climate: Microclimatic Performance and Implications as Potential Wild Bee Nesting Sites

When designing green façades, parameters such as system type, orientation and solar exposure can directly affect the achievement of the intended objectives, like maximizing cooling potential or promoting biodiversity. Using data from 22 façades in southern Germany, characteristic features and their impact on microclimatic properties were analysed. Considering the microclimate as an important determinant of habitat quality in green façades, the potential for these systems to serve as habitats for wild bees was evaluated. During the summer period a temperature decrease was observed from the mesoclimate, as recorded by official weather stations, towards the green façades and their substrate. The factors solar exposure, façade azimuth and the selected green façade system showed the greatest potential impact on temperature, capable of shifting temperatures by more than 2 K. Across both summer and winter, green façades dampened temperature extremes, indicating improved winter conditions and mitigating heat spikes for certain wild bee species that would potentially use the façades for overwintering due to their creating a more stable thermal environment. Thus, our findings suggest that appropriately designed green façades offer the thermal potential to serve as refuges for wild bees in the urban climate, although further analyses with actual abundance data in relation to climate data are required.