Green Wall

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Green Wall at Queen's University, Kingston, Ontario, Canada by Nedlaw Living Walls

A green wall is a wall, either free-standing or part of a building, that is partially or completely covered with vegetation and, in some cases, soil or an inorganic growing medium. They are also referred to as living walls, biowalls, or vertical gardens.

There are two main categories of green walls: green façades and living walls. Green façades are made up of climbing plants either growing directly on a wall or, more recently, specially designed supporting structures. Living walls are made up of pre-vegetated panels or fabric systems that are attached to a structural wall or frame. The modular panels are often comprised of polypropylene plastic containers, geotextiles, irrigation systems, a growing medium and vegetation.^[1]

'Active walls' are a relatively new, experimental concept in which a living wall is paired with a building's air circulation system^{[citation needed]}. Fans draw air through the wall and then circulate the air throughout the building^{[citation needed]}. Air drawn through the living wall is filtered of pollutants by microbes existing in the plants root systems^{[citation needed]}. A variation of this concept are active walls that are kept behind glass to create more predictable airflow effects than inactive walls. 'Inactive walls' have no mechanized air circulation. Instead, they are kept open to promote as much free air circulation as possible.

Living walls are also a means for water reuse. The plants may purify slightly polluted water (such as greywater) by digesting the dissolved nutrients. Bacteria mineralise the organic components to make them available to the plants.

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

The living wall is a form of urban agriculture or urban gardening. It may be built as a work of art for its beauty. It is sometimes built indoors to help cure sick building syndrome.