In the contemporary green architecture, we can find a method which has often been in the media. Sometimes described as ecological revolution, sometimes as mediatical fraud, the green wall is controversial. Let’s try to get more informations about that green architecture system.
A green wall is simply a vertical ecosystem, created by the man, parallel to a facade of a building. Also a kind of large artistic piece, the green wall brings vegetation in a city.
This technique has some direct advantages. First, on a thermical point of view, the plants absorb the rays of the sun, avoiding the increase of the internal temperature due to sunlight. Even without direct exposure to the rays of the sun, a green wall is helping decreasing the heating transfer between inside and outside a building. In the city, this system is also recommended as a solution against the noise. Otherwise, the leaves absorb carbon dioxide, principal greenhouse gas, but also nitrous oxide and hydrogen sulphide, found in city mainly because of the cars. A green wall can be put on a building, regardless its orientation: north, east, south or west. There is always a plant which would be adapted. Finally, this technique offers colors and tones that change during the year, and raise the awareness of the people for ecological architecture.
On the other hand, this technique is very expansive, and this is certainly one big problem of the ecological systems: we don’t talk enough about the costs and the bad consequences. The need for water is high, the plants have always to be wet and irrigated. A simple water cut or a blackout, stopping the pump, would kill the plants and destroy the green wall in a very short time. The maintenance also is expensive, depending on the types of the plants; it is better to use local plants with shallow roots, but these are not disponible in every place of the world. It is also important to check the humidity on the building’s walls to avoid an accelerated degradation.
To all these problems we have solutions. One of the most important criteria of ecosustainable architecture is to use renewable energies. Rainwater and sunlight are part of them. Some photovoltaic pannels on the roof of the building would very easily offer enough energy for the maintenance of the green wall, like the water pump for example. To recover the rain water on the roof of the building would give a solution for the need of water of the green wall: it is possible to stock this water, use it for the green wall when needed, and simply dump the grey water into the sewers of the city, or in a park next to the building, without the need for any treatment.
Nowadays, the people wary about te “miracle products” for an ecosustainable architecture. Not every building is ecosustainable just because it has some wood panels or some plants on it. The problem of the green wall is it huge costs of water consumption and maintenance. However, the main idea is not bad at all, we just have to control all the consequences of this kind of system on a certain building and find solutions to decrease the energy demand and the bad consequences on the environment. To check all the details of a system is a guarantee of its efficiency.
by Jean-Baptiste Hurstel