Performance of greenwalls in Mediterranean climates: a literature review

Green walls have been used for millennia for thermal comfort and aesthetics. The traditional green wall design of vines grown over a trellis, has recently been re-engineered into a variety of possible configurations (living walls, green façades and biofaçades), in an attempt to enhance their performance in urban environments, and also to utilise the systems for treatment of domestic greywater. A key challenge for green walls in the Perth context is their ability to survive Perth’s hot dry summer, and it would be preferable to access research conducted in arid and semi-arid zones on green wall design, performance and viability, costs and maintenance. However, while green wall systems have been used for millennia in drier climates, there is a paucity of research on systems in arid or semi-arid climates. Like all green infrastructure in urban environments, design and performance objectives will vary depending on needs. For urban residential areas, green walls are expected to provide thermal comfort,
and are typically oriented on a building with this in mind. They are also expected to provide amenity and aesthetics. Plant species must be carefully selected for both of these objectives, and in Perth may also be expected to be water-wise.
The objective that green walls also treat domestic greywater requires additional design considerations, including the selection of plants that are not impacted by more plentiful and consistent watering regimes and by higher nutrient supply, the selection of growing media to enhance nutrient uptake, and an irrigation regime that consumes the greywater supply yet optimises saturation regimes in the media. This literature review provides a succinct and critical summary of recent research on green wall performance, and highlights knowledge gaps that may impact on appropriate design and operation of green walls in Perth urban areas. Importantly, we have also carefully defined terminology used for different green wall configurations.
This literature review provides the setting for the establishment of a green façade research facility and demonstration site at the Bentley Primary School, supported by the WA Department of Communities, the CRC Water Sensitive Cities and the University of Western Australia. The project aims to quantify the thermal comfort and greywater treatment performance of green façades, using different wall orientations and plant species.