How vertical gardens are greening Europe's cities
Living walls do more than make buildings look pretty; they can also bring substantial benefits to urban areas.
A growing number of living walls around Europe are helping to make the busy urban centers of its cities that little bit greener.
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.”
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.
“I think that green walls will emerge on more developments in the future, but they need to be maintained by professionals,” Perry says. Certain species may have limited rooting ability, for example, while the additional maintenance cost of pruning and watering skyward gardens must be factored in.
Some modern buildings are already taking the concept further beyond single walls. In Milan, which has long grappled with air pollution, architect Stefano Boeri is pioneering the concept of vertical forests that wrap around residential high-rises. His Bosco Verticale project in the city’s Porto Nuevo district is a pair of apartment towers where 800 trees and 15,000 plants are rooted over the towers’ 111-meter and 76-meter heights, creating a 20,000 square meter area of foliage that is home to local species of birds, butterflies and insects.
The idea is catching on; Paris is planning its first vertical forest tower while Boeri’s firm also has similar projects in the pipeline for Switzerland and the Netherlands, and an even more majestic version, the Liuzhou Forest City in China, which will be a 342-acre neighbourhood covered in 40,000 trees and nearly a million plants.
And living walls can work equally well indoors. The Mandarin Oriental Hyde Park features a wall of landscaped foliage in its internal courtyard, while London’s Heathrow Airport trialled a ‘Garden Gate’ with nearly 1,700 plants to create a sense of calm for departing passengers.
As green walls and vertical forests become a benchmark in modern sustainable design, there is a need to determine how they can improve a particular building’s immediate environment and quality of life for residents and pedestrians.
“Often green walls are seen to soften projects, such as industrial or retail schemes, but there is a danger of this appearing to be ‘green-washing’ rather than providing a tangible positive impact,” Perry says. “Green spaces are shown to maximize visual impact and wellbeing – but why not improve the landscape at ground level as well?”
Indeed, with density in cities on the rise, green areas – whether on the ground, on the walls or on the roofs – become ever more valuable. For many city dwellers going about their busy everyday lives these green spaces provide a breath of fresh air in more ways than one.