Window boxes, roof gardens and the odd plant-covered balcony have long added a splash of colour to the residential towers in our big cities.
Now as architects increasingly look for innovative ways to improve the look and feel of buildings – not to mention their sustainability credentials – a new breed of skyscraper is springing up in Europe and Asia. Welcome to ‘treescrapers’, which as the name suggests, have multiple trees built into balconies rising up the building.
Milan’s Vertical Forest is the prototype of this style, winning the title of 2015 Best Tall Building Worldwide from the Council of Tall Buildings and Urban Habitat. The Taiwanese capital of Taipei is unveiling its own version with the 20-storey Agora Garden which will be home to orchards and herb gardens. These developments build on a growing trend in high level urban construction – softening parts of our concrete jungles by incor-porating greenery into their designs.
But Agora and Vertical Forest – both Gold-certified under the LEED environmental ratings – go farther than other living buildings by planning trees into the design from the start. Trees are far more challenging for an architect to embody into a plan than other vegetation because of their extra size and weight. A problem shrub can be treated or extracted in a few minutes; a problem tree, especially one with penetrating roots, could damage the building.
For a number of architects and their funders it’s a challenge that they are willing to take. Vertical Forest architect Stefano Boeri, who included 900 trees in his design, says the approach is a way of ensuring “the environmental survival of contemporary European cities,” which grow denser by the day.
Also seeded into Boeri’s two residential towers are 11,000 ground cover plants and 5,000 shrubs. The numbers are quite specific – and add up to the same amount of flora that the site’s acreage would host if it were part of a forest, rather than being part of a city.
Boeri is now working on his Tour des Cedres luxury apartment treescraper in Lausanne. With construction due to start in 2017, it takes its name from the 100 cedar trees which will create a vertical woodland over 36 floors. There will also be 6,000 shrubs and 18,000 plants. Boeri says that the tower will make Lausanne “a cutting-edge city in the global challenge to implement urban quality together with sustainability and biodiversity”.
Creating the building’s DNA
But, despite the beauty, visual appeal and air-filtering properties of such buildings, the jury is still out as to whether the treescraper idea will spread to many cities around the world. “It’s not cheap to build,” says Adam Challis, JLL’s Head of UK Residential Research. “The trees have got to be part of the building’s DNA. And so you are hard-wiring the building to that type of use.”
As Challis suggests, there are substantial extra capital costs such as putting in the extra reinforced concrete to support the weight of the trees, plants and soil as well as higher maintenance expenses. A film has even been made, The Flying Gardeners, to show how the ‘botanical climbers’ at the Vertical Forest prune the trees every four months. On top of footing these bills, owners of the buildings have to accept that the use of space for greenery subtracts from the number of square meters left for revenue-raising, commercial pur-poses.
Moreover, as Challis says, the vertical forest approach “is not really what the sustainability of modern buildings is about”. The mainstream of sustainable designers will concentrate principally on techniques such as conserving and generating energy in an eco-friendly way, using the best materials and creating operational building efficiency. Skeptics have suggested that the eye-catching beauty of a vertical forest is achieved by sacrificing some elements of these other techniques.
But, despite these queries about treescrapers, Challis believes that the direction of travel is clear. Noting that sustainable buildings were a major theme of the Climate Change Con-ference held recently in Paris, he says: “Being able to create living buildings is really important.”
More than just green benefits
On the other side of the world Simone Concha, JLL’s Director of Sustainability in Australia, also believes that some elements of the vertical gardening approach will spread around the world – if not necessarily the trees. “Vertical landscaping is definitely the way of the future for cities and it is taking the ‘concrete’ out of ‘concrete jungle’,” she says.
“The innovative aspect is thinking outside the normal design paradigm to dramatically increase the area of landscaping on a building site. Using the structure of the building itself, rather than just the unbuilt upon area of the ground plane maximizes the amount of vegetation that can grow on the site. The biodiversity and wellbeing benefit is huge.”
Not all architects have the budgets that Boeri had and will prefer to use green walls – and even atria which house one large tree at ground level – as far less experimental ways of living the environmental agenda. Sydney’s suburb of Chippendale, for example, is home to One Central Park which hosts 38,000 plants in the “living green walls” of its residential towers.
In the meantime, Boeri and colleagues are working to fine-tune the design of Vertical Forest. Lausanne’s Tour des Cedres is thought to include some modifications that could make it more sustainable. Like the Forest, Tour des Cedres will include features to reduce noise pollution and the ‘heat island’ effect of city buildings but the thermodynamic design appears more efficient.
And, trees or no trees, the shifting balance between greenery and concrete is here to stay. “This is really going to become a trend,” says Concha. “For their health and happiness, people need contact with nature.”