Green facades for cooling urban hot spots

Abstract

To limit increasing heat problems in cities, green areas are being implemented in the urban context. Since space is often scarce, an opportunity lies in the use of green facades. This research has investigated the cooling effect of natural green facades in the form of He¬dera helix. Both the effect on thermal comfort inside and outside buildings was investigated during a five-day heatwave using a model approach in ENVI-met. For this purpose, energy labels and the urban heat island effect were used as heat exposure indicators to determine ur¬ban hot spots in Amsterdam. One study area was selected for which dwellings were simulated for four different orientations, namely facing north, east, south and west. The results demon¬strated that green facades could account for small decreases (<1 °C) in air temperature and outdoor thermal comfort. This cooling effect was more pronounced for indoor temperatures, where the insulating function of the greening led to a maximum cooling of 3 °C for the sou¬thern oriented buildings within the first 24 hours. After a few days, the indoor effect appeared to fluctuate, resulting in lower temperatures during the night and higher temperatures during the day compared to a non-green facade. In conclusion, this research has demonstra¬ted that green facades can reduce the heat accumulation of buildings as they function as an extra insulation layer. Further research may be necessary to determine which accompanying measures can optimize the cooling effect of green facades to limit urban heat problems.