6. A Green Building Envelope: A Crucial Contribution to Biophilic Cities

Throughout history, greening of outside walls and roofs of buildings has taken place. Reasons for doing so were the increase of insulation (keep cool in summer and keep cold out in winter), improved esthetics, improved indoor and outdoor climate, adsorption of particulate matter (PM_x), as well as increasing ecological values by creating habitats for birds and insects. Green façades and living walls systems can improve the (local) environment in cities. They offer more surfaces with vegetation and, at the same time, contribute to the improvement of the thermal performance of buildings. Although in the past, relatively little attention has been paid to these valuable opportunities of vegetation and its interaction with buildings. More and more attention is shifted to these so-called beneficial relations in especially dense urban areas, which can be considered as deserts in biological terms. This movement from a biophilic perspective point of view includes combining nature and natural elements in the built environment to ameliorate the negative impact of climate change as for example loss of biodiversity, mitigation of urban heat, or air pollution reduction.