Central London hotel Athenaeum has seven storeys of lush greenery winding up a corner, while the entire side of Madrid museum and cultural centre, the CaixaForum, is blanketed in plants and flowers. In Paris, the entrance to the iconic Musée du quai Branly is a green wall made of 15,000 plants across 800 square meters – and by 2020, the city aims to have 100 hectares of plant-entwined rooftops and walls.
“Green spaces do more than make the urban environment look more attractive,” says Ashley Perry, Senior Project Manager at JLL. “They often have a positive effect on the wellbeing of city dwellers, helping to reduce stress and improve mood.”
The natural world also benefits – greenery on rooftops and walls can encourage biodiversity by attracting local birds and insects, defuse the heat from dense urban structures and help mitigate climate change. In addition, the profusion of plants along green walls can also improve urban air quality by trapping polluting particulates and removing carbon dioxide from the air, replacing it with oxygen.
“There is an increasing focus on air quality in cities, and green walls or vertical forests are one way of combating pollution within the micro-climate of a particular building,” Perry says. “London’s Mayor Sadiq Khan, for example, is proposing guidelines to increase green infrastructure such as street trees, green roofs, green walls and rain gardens and a framework to help local authorities and developers determine how much should be required in new developments. This will give greater certainty to developers and focus attention on improving urban living in the UK’s capital.”
A smart green choice
For building managers, green walls can represent efficient design – plant-covered walls help mitigate wind impact and insulate interiors. However, not all green walls are created – or maintained – equally.
Deciduous species, which shed their leaves in winter, are better at improving heat efficiency – in spring and summer, leafy boughs contribute to shading from the sun, while in winter, bare branches maximise the impact of weaker sunlight. As a result, Perry notes, green walls are likely best suited to temperate climates with reasonable levels of both sunlight and rain.