In my ongoing obsession with putting earth and plants on city walls I have found some more resources. My ongoing research is for several jobs Eco Brooklyn has in the works to put living walls on Brownstone exterior walls. There are many ways to do this and I have not decided which to go with yet.
My main consideration is maintenance, durability and embodied energy.
The wall must require zero or low maintenance. This means the plants need to take care of themselves year after year. The main consideration is water, which would be provided by the gray water produced by the brownstone. Otherwise the large amount of water a living wall requires would render it unsustainable if it used potable water.
In terms of durability the Brooklyn living wall needs to have plants that don’t die. Obvious enough but easier said than done. They need to be native plants that like hanging on cliffs. There also needs to be a mix of evergreen and perennials. The evergreens would keep the wall from looking bleak in the winter and the evergreens would keep the wall vibrant.
More importantly the structure needs to be durable. Earth and wood are key ingredient for termites so unfortunately we can’t use the abundance of salvaged wood for the frame that holds up the living wall. I don’t want to use the existing brick wall of the brownstone to support the living wall since I don’t trust that it won’t bow out over time. I have seen too many walls do this without thousands of pounds pulling on it.
The obvious choice is a metal framework.
But that needs to be balanced out by embodied energy. A living wall with a metal framework would mean a lot of embodied energy even if the metal was made from recycled content. It takes a lot of heat to melt down metal. Finding salvaged metal is still a challenge for Eco Brooklyn, both in electrical and plumbing material, since scrap collectors get it before we do. We are working on building stronger ties with scrap collectors but so far our salvaged metal sources are scarce.
Anyway, here are some items that are helpful in my growing knowledge of the perfect Brownstone living wall.
UrbanHaBitats.org offers some good articles on urban living walls. They list all their sources for further digging.
This woven plastic may be an important element in a living wall. The material would allow the plant roots to weave into it and help create the support structure. Otherwise the plants and earth will sag with gravity.
Zinco offers holding cells for sloped green roofs that could be incorporated behind a mesh in a living wall. They also have a good moisture retention mat.