Green walls are a paradox; traditionally, architects design buildings to shed water, and building owners want to keep moss and lichen off their buildings. For researchers at Barcelona Tech, (UPC), it's not a bug, it's a feature. They have developed a new kind of wall that will actually promote the growth of moss, lichens and fungi.
It is a clever sandwich that starts with a structural layer of conventional portland cement concrete protected by a waterproof membrane. The designers explain how the rest of it works:
The next layer is the biological layer, which supports colonisation and allows water to accumulate inside it. It acts as an internal microstructure, aiding retention and expelling moisture; since it has the capacity to capture and store rainwater, this layer facilitates the development of biological organisms.
The final layer is a discontinuous coating layer with a reverse waterproofing function. This layer permits the entry of rainwater and prevents it from escaping; in this way, the outflow of water is redirected to where it is aimed to obtain biological growth.
The researchers claim that the biological coating will absorb CO2 and act as insulation and thermal mass. It will also look good:
It can be used to decorate the façade of buildings or the surface of constructions with different finishes and shades of colour; it has been designed for the colonisation of certain areas with a variety of colours, without the need to cover an entire surface. The idea is to create a patina in the form of a biological covering or a “living” painting.
Note that the researchers are from sunny and warm Barcelona; This doesn't sound like it would like a freeze-thaw cycle very much.
Found on Dezeen