This can be great for the wall of your steel building. Here are some advantages to living walls:
Living walls can be designed to slowly use up the storm-water that has landed on the roof or other hard surfaces of a steel building site as its main source of water. As plants in a soil-less design definitely need a relatively constant supply of water, this will probably need to be replenished in hot and dry temperatures. Use of a cistern that slowly drains down into the pockets that the plants are growing out of would work well. Some cleansing is provided by the plants and soils, and some by the bacteria that eventually inhabits the growing pockets and root surfaces.
Living walls trap many airborne pollutants and particulates on the plant surfaces. And, plants use up Carbon Dioxide. A four story high living wall inside the Bell Canada’s Creekbank facility in Toronto is not only beautiful but is designed to remove Volatile Organic Compounds (VOCs) and Carbon Dioxide from the indoor air. There are many companies that market such ‘bio-wall’ as designed for such bio-filtration.
Living Walls also make excellent use of vertical space within cities, providing microhabitat, aesthetic benefits, and air cleansing where none would have typically existed before. The high ratio of wall to roof area in urban spaces means the potential to generate positive environmental changes via green walls versus green roofs is also much higher.
The circulating water in a living wall evaporates less than in a horizontal garden so can work well in drier climates. They can also add thermal mass to steel buildings and their processes help moderate indoor and outdoor building temperature. They provide shade and an insulating dead air space on the surface of the building wall. Vegetation lowers adjacent air temperatures by evaporating enormous amounts of water from leaf surfaces. One Canadian study found the reduction of summer cooling load by living walls was even more dramatic than for green roofs. The same study showed that significant reductions in the urban heat island effect could be attained if living wall technology was used extensively.
The engineered soil-less systems (PVC layer, felt & metal frame for example) can weigh less than 30 kg/m2 – this despite being constantly wet, so are considered fairly light-weight for adding on to existing walls. They can easily meet the habitat requirements of small wildlife species, such as birds and insects; or fish and small pond life if that is incorporated into the design.
Most living walls are designed for artistic effect and to enhance livability by providing calming greenery in very urban spaces. Check out these dramatic large-scale examples in Europe, Asia and the US that were designed by botanists. Green walls can help reduce sound transmission into buildings due to the layer of plants, growing medium and, depending upon the design, the dead air space between the living and conventional walls. While it is hard to find an example of a living wall designed for food growing, some proponents suggest home made versions for greenhouse walls and vegetable gardens.