How green is a green façade? : life cycle assessment of a façade greening at a Swiss hospital
Creators: name: Frehner, Alena
name: Stucki, Matthias
name: Kröhnert, Hanna
Publisher: name: ZHAW Zurich University of Applied Sciences
Year: 2023
Subjects: Life cycle assessment (LCA)
Green building
Environmental impact
Living wall
Façade greening
333: Bodenwirtschaft und Ressourcen
712: Landschaftsgestaltung (Landschaftsdesign)

description: Vertical façade greening, also called green walls or living walls, is recognized as an effective measure to mitigate urban heat islands, to offer additional building insulation, and to promote biodiversity. Yet, it is important to evaluate these positive effects against the environmental impact caused by of the greening systems themselves.
There are numerous scientific studies which compare the environmental impact of small- and medium scale test segments of different living wall systems. Actual façade greening projects, however, do not only follow environmental considerations, but also have to comply with economic expectations, regulations (e.g., concerning fire protection), weight restrictions or existing building structures. 
The goal of the presented study was to obtain comprehensive knowledge on the resource consumption and environmental impact of a full-scale façade greening system, to identify ecological hotspots and to develop recommendations for the ecological optimisation for future projects.
For that reason, a life cycle assessment (LCA) of an existing façade greening in Zurich, Switzerland, was carried out. The analysed system extended over 16 storeys and covered ~3100 sqm. It consisted of planted troughs made of chromium-nickel steel (CNS), placed along the balcony of each storey and connected to an automated irrigation system. Primary data was collected on the entire life cycle of the greening system, including production, operation and disposal of all components.
Assuming a service life of 15 years, the study showed that the façade greening led to greenhouse gas (GHG) emissions of 80 t CO2-eq over its entire life cycle. The corresponding cumulative energy demand amounted to 1.3 TJ oil-eq, with a 75% share of non-renewable energy.
The production of CNS (with an assumed recycling share of 55%) emerged as the main ecological hotspot of the façade greening. If the service life of the façade was extended to 60 years, the environmental impact of the façade greening per year could be reduced by around 15%. Environmental impacts could further be reduced by up to 30 % if 100 % recycled CNS was assumed as material of the planter troughs.
It was estimated that the façade greening contributes about 1% to the environmental impact of the life cycle of the whole building. Nonetheless, the environmental impact should be reduced as much as possible, considering the high contribution of buildings to national GHG-emissions in absolute terms.
An effective measure to reduce the environmental impact of façade greening consists of choosing troughs made of materials with a high recycling share and long lifetimes. In general, the number of troughs should be minimized, and if possible, ground-based greening systems without troughs should be used.
Concluding, it was shown that considering environmental aspects already in the design phase of a green façade project enables to minimize its environmental impact while benefiting from its positive effects.