Green or living walls

Green or living walls are not a new concept but they are increasing in popularity. They can be found insulating and shading building exterior walls, making interior atria come alive and bringing urban spaces such as parks closer to nature. Added vegetation in urban areas not only creates a more pleasant environment but also helps clean the air, reduce noise and can even be used to grow food.

Green or living walls contain soil with fertilizer, which is corrosive even when organic. Additionally, they are kept moist and the soil is aerated (i.e. contains oxygen), which increases its corrosiveness. As is necessary when selecting plants, the presence of coastal and deicing salt must also be considered in the selection of the planter and structural support materials because it will increase soil corrosiveness. Neither carbon steel nor aluminum is suitable for planters because of their high corrosion rates in soil, which are well documented. Plastic planters provide short-term life and must be repeatedly replaced.

The only material that can fulfill the goals of Whole Building Life Cycle Assessment to minimize or eliminate replacement, maintenance and waste in green walls is a molybdenum-containing stainless steel like Type 316/316L. In addition to its documented soil corrosion performance, it has the corrosion resistance necessary for supporting the planters in the damp cavity behind the green wall. Several resources are available in our downloadable library to assist in selecting an appropriate stainless steel alloy including:

• EuroInox’s Corrosion Resistance of Stainless Steels in Soils and Concrete
• JSSA/Nickel Institute, Japanese soil corrosion data (12005)
  • Vol 1 summary of stainless steel, carbon steel, copper and lead corrosion data from 25 locations
  • Vol 2 test location data and photographs
• US Government Corrosion data Underground Corrosion After 32 Years: A Study of Fate and Transport