The Triptych Green Wall

Location:                     8-10 Kavanagh Street, Southbank, Victoria

Completion date:      2009

Area:                           206 m² on a new building

Description

Triptych Apartments include a large hydroponic green wall on the building’s exterior south-east facade, extending up from the second level, above the footpath. It is visible to all vehicular and pedestrian passers-by, and is viewed by neighbouring office and apartment buildings.

Introduction

Visible from the street, the green wall feature was considered by the developer to provide a ‘wow-factor’, setting the building apart from other inner-city residences and blending in with the leafy streetscape.

The purpose of the green wall was to:

• obscure the view of the exterior of the multi-level parking area
• use foliage to soften the built environment
• provide habitat and increase diversity through the use of native and exotic plant species
• utilise collected rainwater.

The property was owned by the Stable Group, and the project was completed by Nettletontribe architects and green wall specialists, Fytogreen.

Design and components

The wall includes 362 planting panels measuring 100 cm x 500 cm x 15 cm along with 44 planting panels measuring 75 cm x 50 cm x 15 cm. It is designed for a weight loading of 80kg/m² dead load.

A spray-on waterproofing material was used. A root barrier layer was not required because the air barrier between the wall and the modular system allows for air pruning. (Roots become exposed to the air, which dehydrates them and stops them growing further.) Polyurethane foam, a Fytogreen patented product, with felt wrapping was used as the growing medium. The foam modules are held in a steel cage, mounted on a wall using steel brackets.

Plants are irrigated using a controlled release dripper system that runs to each separate module, using collected rainwater supplemented with mains water as required. Fertiliser is also delivered via the irrigation drip system. The stainless steel facia surrounding each panel guides any excess moisture to a steel drip tray at the base of the vertical garden.

Irrigation equipment includes a controller for timed irrigation cycles; a fertigation system for controlled fertiliser dosing through the irrigation system; water meter; pressure gauge; controlled volume drip irrigation line; and water storage tanks, filters and pumps.

Native and exotic plant species, chosen for aesthetic appeal, durability and biodiversity, are featured. The planting plan considered the differing levels of sun and shade across the wall surface, and the impact of plants shading one another as they grew. At 15 plants per panel, a total of 5,958 plants was required. For the planting stock, 140 mm container specimens were grown in an offsite greenhouse for eight to 12 weeks before installation. The benefit of using fully-grown plants is the immediate visual impact when installed.

The swathes (planted sections of different species) were specifically designed to control lateral wind movement over the host wall surface, either mitigating wind damage or creating niches for species in the leeward sides.

In addition to aesthetic appeal, plant species were chosen to be hardy, low maintenance and shade tolerant. Many of the species feature coloured foliage or flowers throughout the year, contributing to the beauty of the design.

Careful consideration was given to the combination of species used, and their placement in relation to each other. All species were selected to offer cumulative control of pests and disease spread, wind, light and moisture, and to manage competition between species. The long-term growth patterns and likely reaction to the environment were also considered. High foliage coverage was sought for visual appeal and also to out-compete weeds. 

Maintenance

By choosing species that respond well to each other, the green wall requires less maintenance than a more rigid design. The owners favoured this approach because it offered a long-term, adaptable and sustainable solution.

Fytogreen is contracted to undertake the maintenance. Maintenance is moderately fluid, pending seasonal changes and the client’s aesthetic expectations. The Triptych owners embraced natural aesthetic forms and ongoing species self-adjusting, leading to a less restrictive maintenance process. Knuckle Boom lift access, requiring a small team of horticulturists, is generally conducted every three months.

Monthly checks, conducted by one person, assess water supply, quality and general garden condition.

Cost

Total: $350,000.

This budget included a 12-month contract with Fytogreen covering maintenance of the green wall and defects liability. After this time, the maintenance contracts were negotiated between the parties and open for tender.

Results and reflections

Fytogreen reports that this is a statement green wall that has proven to be functional in terms of water usage, visual impact and has assisted with the selling of apartments. Using harvested rainwater form the building the plants are thriving and habitat is being created. Fytogreen notes the visual amenity provided to all surrounding parties, including passers-by.

In retrospect Fytogreen states it would have changed only one thing, and that was to have set up the wall to also be a research space for vertical garden species.

Fytogreen concludes that this is a large-scale green wall that puts Melbourne on the map. As it is free to view to all passers-by it provides inspiration to all to question technology, property value and the impacts of vegetation on built surfaces.