We love the idea of a city full of houses with plants on the walls. Our vision is to make the polluted cities with lots of plants cleaner and improve the living conditions. Besides, it looks great walking along a street full of green houses. Green is the colour of happiness! We are convinced that people in the city would feel much better because of the colourful effect of their neighbourhood. We could create a living room for many insects and for example some herbs right under the windows.
What is a green wall?
A green wall is a wall covered with greenery. It can be indoor or outdoor. And most of the green walls have an integrated water delivery system.
It depends if the green wall is indoor or outdoor because the plants need to match their future surrounding.
The difference between green walls and facades is, that green walls have soil overall the face of the wall, whereas green facades only have soil on the ground. Green walls are becoming more and more popular. (Wikipedia, 2019)
The City of Zurich and its green walls
In Zurich City you can find a facade-bound green wall in the Hunziker Area (zuerich.com) and Maag Area (bing.com). Furthermore, there are earth bounded green walls in the MFO-Park (site of the former Maschinenfabrik Oerlikon, see photos below), Parking Area Sihlcity (map.search.ch) and in the Neufrankengasse, Zurich (map.search.ch).
Here you can get an overview: list of vertical greening in Zurich City 2019 (PDF)
Most important is, that there are new green walls planned in the Kochareal and in the school area at Thurgauerstrasse (mapsearch.ch). The market for green walls is still very small but there is a huge potential to expand and multiply the green walls in and around Zurich.
Luckily there are just a few regulations or legal requirements in Zurich. Therefore you can easily adapt plants to a wall if you want to. You do not even need a planning permission. One problem could be the walls from houses, which do not have a front yard. There the plants could be on an interface between the private and public ground and further clarifications must be made. (Michael Fuchs, Grünstadt Zürich, January 2020)
But if you want to implement a green wall, there are still a few points which you should take care off. We suggest you the following checklist with a few tips in German: Checkliste Vertikalbegruenung GSZ (PDF, Grünstadt Zürich, zuerich.ch)
And if you are really really interested in the topic, the following report “Gebäude Begrünung Energie, Potenziale und Wechselwirkungen” (PDF, 99 MB, Building greening Energy, potentials and interactions, Germany) is also highly recommended.
As you can read in our article, green walls have a huge impact on our environment. Every large plant in front of a glass or steel facade, that prevents direct sunlight, minimizes the temperature on the facade multiplicative. With a few plants in front of your window you can already make a huge contribution to reducing air pollution and helping our environment!
The positive impact of green walls
The scientific research on green walls systems and their benefits in the environment of the cities is still in the development stage. But the studies published so far show consistently positive characteristics, especially for the environment they have multiple positive impacts.
Green walls are most useful on inner-city locations with little ventilation (Durchlüftung) and densely (dicht) built quarters especially on the west and east facades in cause of the solar radiation.
During the day, facades and roof surfaces heat up in the infrared range of sunlight. This heat is transferred to nature and causes a lot of air heating. A green wall would hold back this process and reduce the absorbed heat. In extreme examples up to 100%.
Example of the cooling effect of natural sun protection via tub plants:
(Measurements in August 2011 at the “Flower Tower” project – south side in Paris)
During the night or in winter green walls keep the heat inside the wall and have an isolating effect. In addition to this, the air of the greenery is purified (gereinigt) by filtering out dust and binding fine particles on the leaf’s surface. The plants bind CO2 and produce oxygen through the photosynthesis process.
Moreover, noise reduction and preventing channels from flooding are some positive impacts of green walls as well. (Nicole Pfoser, 2013)
And last but not least as you can see in our headbanner, where we have modified the facade of our school with plants, green walls look so much nicer than the normal grey walls.
Disadvantages of a green wall
Green walls have almost no disadvantages but one disadvantage is the cost of a green wall. If you do not make it by yourself, the costs can get up to CHF 500 per m2. On a facade bounded green wall even up to CHF 1500 per m2 inclusive a drip irrigation system. Furthermore, it requires more maintenance than a normal wall, a little bit like a garden. Dead plants need to be replaced and fallen out earth must be cleaned away. (Hussak, 2020)
How is the set-up of a green wall?
There are various types of set-ups for a green wall. Each company is using a different kind of set up, so it depends on which company you are working with. One of the most common set-ups is the drip irrigation system (Tropfbewässerungssystem).
With the drip irrigation system, the plants are perfectly watered. It prevents the upper plants from drying out and dying, as well the lowest ones from overwatering. On the bottom of every pot is a water tank, grace to this tank the plants only need to be watered once a month. Excess water is deduced (ableiten) through a pipe.
The irrigation process ensures optimal conditions for the plants in every environment.
We conducted two interviews to receive up-to-date information about vertical greening:
During our project we could learn a lot about green walls and our assumptions were confirmed. We were very surprised that building a green wall is that easy. Many of the people who supported us during the project were very helpful and full of euphoria. We enjoyed working on this project and are happy about the final result!
Last but not least, as you can see in our head banner, we have photoshopped the wall of our school and decorated it with some plants. It really looks so much nicer than before!
Yes, it really is that easy – So let’s plant some plants!
Thank you for reading.
Manuela Zeller, Anja Jörger, Raffael Hofmann
Contribution of the collaboration teams from Antwerp: Green walls
Hussak, A., 2019 (kommunal.at), Gute Gründe für Grüne Wände (Good reasons for green walls).
Natural Greenwalls (naturalgreenwalls.com)
3 Typen Pflanzenwände (naturalgreenwalls.com)
Nicole Pfoser, N. J. et al. (31. 08 2013) “Gebäude Begrünung Energie, Potenziale und Wechselwirkungen” (PDF, 99 MB, Building Greening Energy, potentials and interactions); the report was funded by the research initiative Zukunft Bau of the Federal Ministry for Building, Urban Affairs and Spatial Research, Germany
Checkliste Vertikalbegrünung (PDF in German (Checklist vertical greening), Grünstadt Zürich, zuerich.ch)
Green wall (wikipedia.org)
Reducing Urban Heat Islands: Compendium of Strategies, Urban Heat Island Basics (PDF)
Technische Universität Darmstadt, Fachbereich Architektur, 2016, Gutachten Fassadenbegrünung (PDF)
Bosco Verticale (Vertical Forest), Milano, Italy (wikipedia.org)