08/10/2009

blanc = vert


"Do plants really need soil? No they don't.... The soil is merely nothing more than a mechanic(al) support.Only water and the many minerals dissolved in it are essential to plants, together with light and carbon dioxide to conduct photosynthesis.

The core innovation is to use the root's ability to grow not only on a volume (of soil, of water, of sand,....) but also on a surface. Without any soil, the plant-supporting system is very light and thus can be implemented on any wall, whatever it's size."


Patrick Blanc, Botanist and Artist.

How

A metal frame is attached to the load-bearing structure, but separated from it to permit ventilation and prevent root penetration. The frame supports a 10 mm PVC plate, to which are stapled two 3 mm layers of polyamide felt . These layers mimic cliff-growing mosses and are support the roots of many plants. A network of pipes and valves supplies a nutrient "soup" containing dissolved minerals needed for plant growth. The felt is soaked by capillary action with this nutrient solution, which flows down the wall by gravity. The roots of the plants take up the nutrients they need, and therefore do not seek extra water or food by penetrating the building fabric. Excess "soup" is collected at the bottom of the wall by a gutter before being re-circulated within the closed circuit pipe network. Plants are chosen for their ability to grow on this type of environment and for their ability to survive with the available light. The overall depth, including the metal frame, is 100 cm, and the load is about 30 kg/m2. The system was patented by Patrick Blanc in 1988.



Why

Green walls are are most efficient within urban environments where the plants reduce overall temperatures of the building which in turn reduces energy consumption. The primary cause of heat build-up in cities is insolation, the absorption of solar radiation by roads and buildings in the city and the storage of this heat in the building material and its subsequent re-radiation. Plant surfaces however, as a result of transpiration, do not rise more than 4–5 °C above the ambient and are often cooler.


Green walls may also be used as a means of water reuse. The plants may purify slightly polluted water (such as greywater) by absorbing the dissolved nutrients. Bacteria mineralize the organic components to make them available to the plants.


Green walls are particularly suitable for cities, as they allow good use of available vertical surface areas when horizontal sufaces are at a premium. They are also suitable in arid areas, as the circulating water on a vertical wall is less likely to evaporate than in horizontal gardens.

Green Walls and/or Vertical Gardens can also be integrated into a building's air circulation system. Active Green walls are based upon the sciences of biofiltration and phytoremediation. Green walls with biofilters increase the capacity of air filtration, harnessing nature's cleansing power by drawing air through the root system of the wall. Beneficial microbes actively degrade the pollutants in the air before returning the cooled and cleansed fresh air back to the buildings interior.



The green wall by Blanc at the Caixa Forum in Madrid (Hertzog & De Mueron), for example, has an area of 460m2, comprising 15,000 plants of 250 different species. It provides a perfect visual counterpoint to the Corten steel clad extension to the existing building.

2 comments:

e! said...

These are really cool. Very educational as well! ellen

teillu said...

Let's them build gardens on our façades, and they'll start building windows in our floors... :S

That's not a garden if a cow can't eat from it, IMPO.

(Nice to hear from you again! That's Mateo speaking ;P)