Green wall systems may vary enormously, these are two general types. - modular, which can be hydroponic or substrate based, and felt covered hydroponic panels. Note that the support structure and waterproofing are optional and depend on the site.
Green Walls Reduced Energy Costs. "Exterior living walls give buildings protection, not just from temperature fluctuations but also by diverting water away from walls during heavy rain and providing protection from UV radiation."