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Can 'Living Walls' Help Buildings Become Carbon Neutral?

By: Kathryn Senior PhD - Updated: 21 Aug 2012 | comments*Discuss
 
Living Walls Carbon Footprint Carbon

The walls of many buildings and garden perimeters have life on them but this is not generally planned. There are also limits to the type of plant or living organism that can be grown – climbing plants such as ivy and Virginia creeper use walls for support, but their stems and roots are anchored to the soil in the ground near to the wall. Mosses and lichens can cling to the wall and gain enough minerals and water to survive their without any direct access to the soil below, but these never grow more than a few millimetres in height, and their coverage is usually minimal.

The concept of the living wall, or biowall, is completely different. This is more of a vertical garden, in which plants cover the surface of a large vertical wall completely. In fact, the plants and vegetation tend to be so thick that it is virtually impossible to see the original wall at all. In most cases, living walls are devised and planted by human intervention, they do not occur naturally, and are usually part of the building design.

Green Facades and Living Walls – What is the Difference?

Both can be classed as living walls but there are two categories depending on whether the plants are growing in the soil below or whether they are growing in medium that has been placed on the vertical face of the wall. The former is a green facade and involves cultivating climbing plants and trailing plants to give the effect of a wall that is covered in plants. Green facades are generally more common, and can arise when climbing plants grow out of control.

Living walls are, in contrast, always planned structures. A wall is chosen for the project; this is usually an outside wall, but smaller inner living walls are possible. The wall surface is clad with matting that encloses growing material, such as compost, and this is attached to the wall so that it forms a padded layer. Plants can then grow up the wall from the base, or they can be planted within the layer of growing medium.

Irrigation is very important; the plants at the top of the wall are likely to be more exposed to sunlight and will be affected more by the air flow and wind, so are more likely to dry out.

Short and Long Term Living Walls

Living walls that use coir matting or similar materials to enclose a thin layer of rooting medium can support a lush and impressive living wall for up to 3 seasons before they then need to have significant repairs. As the roots of the plants grow through the matting, the ability of water to move through the system becomes reduced. Eventually, the irrigation system fails and the matting needs to be replaced.

A living wall can last 10 years or more if it is made by building a second wall of growth blocks in front of the structural wall. In very sophisticated designs, the composition of the different blocks can be varied, so that the wall can support plants that like to grow at different acidity and alkalinity levels, and those that required more sandy soils can also be accommodated.

Living Walls: Can the Make a Building Carbon Neutral?

The inventor of the living wall is Patrick Blanc, a French botanist who works for the National Centre for Scientific Research in France. His first living wall project was finished in 1988, for the Museum of Science and Industry in Paris. One of his most recent is the green wall in Gdansk in Poland, which was finished in 2008.

Although living walls are extremely impressive and are a type of living work of art, they also serve a practical purpose. The oxygen they produce during the day when it is sunny, using the process of photosynthesis, can be collected and fed through to the inside of the building, to give cleaner air to the people living or working there. Although its environmental impact is not enormous on a global scale, and it can only help a building to move towards becoming carbon neutral, the living wall can enrich the local environment of a building, and can also give a great deal of aesthetic enjoyment for local residents, workers and visitors.

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