Vertical green infrastructure (VGI) has a great potential to support climate transition of compact urban areas. VGI does not compete for land use, but is able to support microclimate regulation through cooling capacities, to reduce noise pollution, to recycle and upcycle rainwater and grey water, to produce food or habitat for species, and to generate pleasant green spaces, with a significant aesthetic value. From a built environment perspective, these solutions can enhance buildings’ performance by protecting and increasing the durability of wall coverings [1], reducing energy consumption, improving photovoltaics panels’ efficiency [2] and reducing sound transmission [3].
Green walls and roofs can use the functional benefits of nature to maximize buildings performance and contribute to a sustainable strategy for urban regeneration and retrofitting of buildings. In this sense, depending on the city morphology and plans, green walls can also have a greater potential than green roofs, considering that in urban centres the extent of facade greening can be double the surface of roofs [4].
Green wall, Liverpool, United Kingdom. Urban GreenUP. Source: https://www.urbangreenup.eu/cities/front-runners/liverpool.kl#lg=1&slide=3.
VGI can be of various form, ranging from green fences and barriers to green walls to vertical mobile and living gardens. Each technology can adopt multiple design features such as different plant species, substrate compositions, among others. The design has impact on the performance of the final solution, also depending on local climate, buildings’ orientation and urban morphology.
Generally speaking, there is a clear distinction between green facades, where climbing plants grow along the wall and cover it, and the concepts of living walls and vertical mobile gardens, which include materials and technology to support a wider variety of plants, creating a uniform growth along the surface. These solutions bring a wider variety of plant species to green walls, allowing the integration of shrubs, grasses and several perennials as long as their watering and nutrient needs are taken into account [5]. Climbing plants are considered a cheap solution of vertical greening, while vertical living walls allow for exploration of new species and vegetation, also exploring the use of patterns, variations in colour, texture, foliage shape and density, vitality and growth. Examples of VGI projects can be found in Naturvation, Urban GreenUP, ProGIreg, and Vertical Green 2.0.
Green façade, Valladolid, Spain. Urban GreenUP. Source: https://www.urbangreenup.eu/cities/front-runners/valladolid.kl#lg=1&slide=9.
Vertical green infrastructures can also be integrated with other solutions, such as low-carbon, efficient, and sustainable building materials – reducing GHG emissions by combining energy efficiency with CO2 capture [Green INSTRUCT].
Vertical Garden, Torino, Italy. ProGIreg. Source: https://progireg.eu/nature-based-solutions/green-walls-and-roofs/.
MATURITY:
Available on the market
VGI such as green facades (e.g., climbing plants and hydroponic green facades) can be considered as already widely available on the market.
Demonstration and deployment
The more recent concepts of living walls – including materials and technology to support a wider variety of plants and integrating technological and natural components – are currently in the demonstration and deployment phase. Most recent developments in green walls are mainly focussing on systems design and their elements (supporting elements, growing media, vegetation, irrigation and drainage) in order to achieve more efficient technical solutions and a better performance in all building phases (installation, maintenance and replacement).
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