Fremantle Greenskins: Green Wall Trials in a Challenging Climate
February 2014
Post by Jana Soderlund
In 2011 a local council in Perth, Western Australia imposed the construction of a green wall as a condition of development for a builder of a block of units. This was because the intended units would obstruct the view of an existing block of units. The council saw a green wall as a beneficial and attractive addition that would mitigate the loss of the view for the current tenants of the existing units. The developer took the council to court over this condition, won the court case, and had the condition removed. His defense was the lack of precedence in Perth and local knowledge with this scale of green wall construction in local climatic conditions.
This initiated the recognition of the need to trial green wall plants and systems in the climatic conditions of Perth and the suburb of Fremantle so the precedents and knowhow were available to future developers. Globally there are many examples of successful green walls but few in similar climatic conditions to Fremantle, where there are long, hot summers, high evaporation rates, and salty sea breezes.
Curtin University Sustainability Policy Institute along with the City of Fremantle established a partnership to trial green walls in Fremantle. In early April 2013 two trials, green walls were installed in Fremantle after 3 months of growing off-site. Two sites and two different green wall systems were chosen. Challenging sites, both socially and climatically, were intentionally chosen. Site A is a north-facing wall in a little-used mall with significant anti-social behavior. The area is a sun trap in summer with a high level of radiant heat from the paving and surrounding walls. Site B is a west-facing street scape wall, again with anti-social behavior. It is more exposed to the late afternoon westerly sun and strong sea breezes.
They are planted with species chosen for their resilience in hot dry conditions, comprising a combination of local plant species and exotics. Both sites are fertigated with a monitored watering system.
Temperature and humidity sensors have been installed and are providing continuous data over the year-long trial period. They are located behind the wall, in the plant canopy, and 15cms out from the canopy. Sensors are also installed on a blank control wall and behind a wooden panel to gauge any difference the plants have on the parameters being measured. Water meters at Site A are measuring water in and water out so evapotranspiration rates can be extrapolated. Plant growth rates are regularly visually assessed to determine which species are thriving. Thermal imagery also will provide visual data on which plant species are providing greater cooling capacity.
Assessment of the social response to the green wall is an important component of the trials with pedestrian counts and behavioral mapping undertaken before the installation of the walls. These are being replicated at different periods throughout the year-long trial. Intercept surveys will be conducted at both sites. On-site signage offers information on the project as well as a QR code link to the website and online survey.
The responses to the green walls have been very positive. Nearly 50 people attended the early Friday morning opening in April, exceeding expectations, with continuing media coverage in local papers, radio interviews, blogs, and websites.
The number of online survey responses is steadily growing and providing some interesting results. When asked for one word to sum up thoughts around the green walls words such as ‘brilliant, positive, breath, inspiring, alive, unique, beautiful’ are being used.
Questions to gauge peoples’ response to nature, in general, are revealing a strong appreciation of beauty. The highest response of 84% strongly agreeing is to the statement ‘I enjoy the beauty of nature’. This is higher than ‘Being in nature is a great stress reducer for me’(79%) and ‘I need time in nature to be happy’(55%).
Where the survey asks questions regarding peoples’ perception of the functional attributes of green walls, again the appreciation of beauty is reflected with 86% strongly agreeing to the statement ‘Green walls can help make a city more attractive and liveable’. By comparison, ‘Green walls could help reduce heat reflected off streets and buildings’ had 62% strongly agree and ‘Green walls can help preserve nature’ had 57%, 95% consider that the City of Fremantle should make provision in their budget for more green walls.
The green walls were intentionally installed in our mild autumn and the plants all thrived except for one species which had to be replaced after 5weeks. They have survived the winter storms and are currently enduring hot summer conditions. There has been no vandalism but much appreciation and interest. Some of the species have just failed after 7weeks of the summer sun, no rain, and high evaporation. These are being replaced. The other species are green and lush providing a workable pallet of suitable species to choose from for future green walls in our city.
Further information and the survey can be found at http://sustainability.curtin.edu.au/projects/