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

Positive effects on landscape aesthetics

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

Vertical greening systems

A. Medl et al. / Building and Environment (2017)

So many types of climate…

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

Executive Office Building at Nanjing University (Yin et al., 2017)

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

Are Green wall systemssustainable?

NUMBERS NEEDED!!

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.

Energy requirements and payback periods for three climates

One example of Life cycle inventory model components

2 environmental accounting methods

• Life Cycle Assessment (limited to the Carbon Footprint)

• EMergy Evaluation (EME)

performance of VGS in a Mediterranean climate.

Carbon Footprint: results from the LCA compared to energy saving

Energy saving for heating, cooling and temperature decrease for Mediterranean and temperate 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.