Green walls (GW) were originally developed for greening buildings and cities, and making them aesthetically more attractive. However, keeping the plants alive with tap water and chemical fertilizer, as is common practice, adds considerably to the life cycle impact of GW. Grey water on the contrary is a free source of water and nutrients, and excess grey water that exits the GW partially treated is often suitable for recycling to low-quality applications. In addition, GW have many other environmental benefits such as reduction of energy consumption and capturing particulate matter from the air which have a positive effect on the life cycle impact. In the presentation, two concrete cases of greywater recycling with GW will be discussed, one from a terraced house in Ghent (Belgium), and one from the office building Kamp C in Westerlo (Belgium). Apart from the greywater treatment capability, also the life cycle impact and practical aspects will be discussed.