From the top to the bottom of the sides of the six-floor building that face north and south, green concrete planters sit below each row of ribbon windows. Even though the building project has only just been completed, some 300 plants and shrubs are already growing across 180 square metres.

Designing green buildings at the tender stage

At the end of 2016, Allreal, the owner of the Escher-Wyss industrial area, conducted a study contract involving eight prestigious architecture firms for a new build to replace an old building located at Hardstrasse 299/301. The architects were asked to look into the concept of plants on the outside of the building and to report back on their findings at the tender stage.

The architecture firm that eventually won the tender, Zurich-based Caruso St John Architects, incorporated this requirement as a fundamental feature of the design from the word go. Ferdinand Schmidt, the lead architect working on the project, says: “We included the lines of planters on every floor in our very early designs and made them a unique feature as part of the building’s structure.” Adding greenery to a building works best when it is incorporated into the design like this. That’s why other ways of adding greenery to the building, such as vertical and ground-based plant climbing support systems, were soon dismissed. “Alongside the environmental considerations, we wanted to make sure that the greenery added character by giving the building itself and the surrounding area by Hardbrücke a truly distinctive feature”, explains Schmidt.

ghiggi paesaggi Landschaft & Städtebau GmbH, a company specialising in landscape architecture, selected plants and shrubs that would give the building a new look with each new season.

Helping to combat overheating in the city

But why is it so important to add so much greenery to buildings in city centres anyway? Reducing the urban heat island effect is one of the hot topics being discussed by city planners and architects right now. The effects of the heat are felt so much more intensely in cities than anywhere else on hot days and so authorities are working to come up with measures to combat overheating. The city of Zurich created a resource with more than 200 pages dedicated to plans to reduce overheating for municipal and private property owners at the start of 2020, with a view to boosting Zurich’s climate credentials. These plans set the objectives of avoiding overheating across the whole city, working specifically on the hardest-hit areas and maintaining the cold-air system already in place in Zurich.

Adding greenery to the outside of buildings is one potential way of achieving these goals that has been left to building contractors and planners in the city to tackle on their own initiative. Ways of incorporating plants into building designs and the benefits of doing so are covered as part of private approval processes.

There’s no question, then, that environmental aspects are an important factor here. As a general rule, any way of expanding the amount of green space in the concrete jungle that is Zurich-West is welcome. This provides more scope for managing rainwater, helps clean the air and remove dust particles, and improves biodiversity.

On top of all that, buildings covered in plants are naturally protected from the sun, with sunlight being reflected away more effectively. Adding greenery can therefore drop the temperature of a building front by up to 6 degrees. Not to mention that employees are treated to a pleasant working environment.

Glorious building fronts covered in plants do still pose some problems, however. For one thing, designing and producing the planters isn’t easy and takes time. One reason for this is the associated watering and drainage mechanisms, including a system to stop them from becoming waterlogged. They also need to be safely accessed by gardeners via windows and walkways without there being any risk of falling. Not to mention that the plants need to be tended to two or three times a year.

Looking at the bigger picture

According to Murat Özküp-Steiner, Head of Project Development at Allreal, the minor additional costs involved in the upkeep of plants and shrubs never stood in the way of getting this project off the ground. “The extra building maintenance costs are inconsequential considering the rental income of a building of this size. In actual fact, the natural shade on the south-facing side means that less energy is wasted on air conditioning during the summer months.” But aren’t we just talking about a drop in the ocean here? “On their own, the measures we have implemented to improve the local climate conditions may not be major, but it’s all about looking at the bigger picture and playing our part. We also took other steps in favour of nature in the city as part of this building project. For example, when designing the outdoor spaces, we set up piles of stones for lizards and nesting areas for swifts and kestrels.”