Greenery vs traditional envelope: a life cycle assessment

In last decades, environmental aspects and in particular energy consumptions related to whole building life cycle have become an important field of research both at institutional level and in the discussions of a public opinion which is increasingly sensible to these aspects. At the same time new kind of building architectural envelopes have spread and diffuse. Among these particular claddings a vertical greenery called Living Wall, find a place. A Living Wall is a vertical garden sawn on a felt which is fixed upon an artificial structure directly installed on the building envelope. A contribution to the reduction of the so called Urban Heat Island effect is given by the cladding itself thanks to different aspects such as low absorption of solar radiation, evapotranspiration phenomenon and high emissivity of the plants. It is demonstrated that green claddings highly reduce the impinging of solar radiation on the building envelope with direct reductions of cooling energy consumption during the summer period. However Living Walls directly interact with the whole life cycle assessment adding environmental costs due to their manufacturing processes. The aim of this work is to compare a Living Wall against a traditional wall by means of a cradle to grave LCA analysis. Usually the assessment of energy consumptions of the building and its interaction with the built environment are only evaluated during its operating period, excluding, as a matter of fact, the amount of energy related to the processes before the operating period. This energy is called embodied energy and it is a key parameter to evaluate the actual goodness and environmental impact of a design solution. In this work, a standard office building made up of a traditional envelope of masonry wall with external insulation is considered and compared, in terms of Life Cycle Assessment, against the same wall with a Living Wall cladding installed on it. Different Window-To-Wall Ratio and insulation levels have been considered in order to cover different existing cases