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Are Green wall systemssustainable?
Lučka Kajfež BogatajUniversity of Ljubljana
Direct green facade, Portugal
M. Manso, J. Castro-Gomes, Green wall systems: A review of their characteristics, Renewable and Sustainable Energy Reviews, 2015
Continuous living wall system, Madrid
Indirect green façade, Hong Kong
Analysis of environmental performance of indoor living walls using embodied energy and carbonInt J Low-Carbon Tech. 2016;12(2):67-74. doi:10.1093/ijlct/ctw021
Indoor living walls
Green wall systemsbut there are so many types…
Green walls
Green facades
DirectTraditional green
facades
IndirectContinuous guides
Modular trellis
Living walls (LWS)
Continuous Lightweight screens
Modular
Trays
Vessels
Planter tiles
Flexible bags
COMMONLY CITED ADVANTAGES
• a work of art• more options for those with limited space • increasing the biodiversity and ecological value• mitigation of urban heat island effect• outdoor and indoor comfort• insulating properties• improve of air quality• improve social and psychological well-being of
city dwellers• new jobs, profitable business
Green facades
Direct greening
Traditional green facades
Limited plant selection /Climate adaptabilitySpontaneous vegetation development Slow surface coverageScattered growth along the surface Surface deterioration /Plants detachmentMaintenance problems
Indirect greening
Continuous guides
Limited plant selection /Climate adaptability Slow surface coverageScattered growth along the surface High environmental burden of some materials
Modular trellisLimited plant selection /Climate adaptability High environmental burden of some materialsHigh installation cost
Living walls
Continuous systems
Felt Pockets Vertical gardens
Complex implementation High water and nutrients consumption Frequent maintenance Limited space for root development High installation cost
Modular systems
Trays
Complex implementation Heavier solutionsSurface forms limited to trays dimensionsHigh environmental burden of some materials High installation cost
Planter tiles
Complex implementation Limited space for root development Surface forms limited to tiles dimensions High installation cost
Flexible bags
Complex implementation Heavier solutions due to growing media/ Limitedto buildings maximum load High installation cost
Green wall systems disadvantages
Green facades
Direct greening
Traditional green facades
Limited plant selection /Climate adaptabilitySpontaneous vegetation development Slow surface coverageScattered growth along the surface Surface deterioration /Plants detachmentMaintenance problems
Indirect greening
Continuous guides
Limited plant selection /Climate adaptability Slow surface coverageScattered growth along the surface High environmental burden of some materials
Modular trellisLimited plant selection /Climate adaptability High environmental burden of some materialsHigh installation cost
Living walls
Continuous systems
Felt Pockets Vertical gardens
Complex implementation High water and nutrients consumption Frequent maintenance Limited space for root development High installation cost
Modular systems
Trays
Complex implementation Heavier solutionsSurface forms limited to trays dimensionsHigh environmental burden of some materials High installation cost
Planter tiles
Complex implementation Limited space for root development Surface forms limited to tiles dimensions High installation cost
Flexible bags
Complex implementation Heavier solutions due to growing media/ Limitedto buildings maximum load High installation cost
Green wall systems disadvantages
Life-cycle Analysis
Any attempt to evaluate the benefits of green facades must
follow the framework established by a standard LCA
methodology with a reasonably realistic set of assumptions.
LCA DefinedISO 14040 (‘97)
Goal &
Scope
Definition
Inventory
Analysis
Impact
Assessment
Life Cycle Assessment Framework
Interpretation
Direct Applications:
* Product Development
& Improvement
* Strategic planning
* Public policy making
* Marketing
* Other
16
The Three Steps of LCA
1. The Life-cycle Inventory
– What are the energy, raw materials, emissions, & wastes? What data are needed?
2. Life-cycle Impact Analysis
– Assess environmental impacts identified in the life-cycle inventory.
3. Life-cycle Improvement Analysis
– Identifies opportunities to reduce the environmental impacts by modifying of the life-cycle inventory.
Green wall systems composition
Green wall systems by their nature are complex systems, as are the sustainability issues to which they connect such as climate change, peak resources and land occupation. Life cycle assessment (LCA) can drive reduction of environmental impacts , by tying design decisions to impact reductions for contexts now, and those envisaged for the future.
2 environmental accounting methods
• Life Cycle Assessment (limited to the Carbon Footprint)
• EMergy Evaluation (EME)
performance of VGS in a Mediterranean climate.
Concluding thoughts
• There is still a huge research gap regardingsustainability of Green wall systems (more climates, over the whole year, lack of research on orientation,evapotranspiration and shading must be analysed,lack of studies, especially in arid climate)
• Green wall systems must evolve to become more sustainable solutions, through the use of materials with less incorporated energy and CO2 emissions and the application of climate adapted plant species with less irrigation needs
Concluding thoughts
• Some examples already show sustainability concerns by using natural or recycled materials and native plants, integrating water recovery systems and sensors for water and nutrients minimization.
• The decision of which green wall system is more appropriate to a certain project must depend not only on the construction and climatic restrictions but also on the environmental impact of its components (e.g., energy or water used and materials recyclability) and associated costs during its entire lifecycle.