Installing and managing your green wall
Plant selection will depend on a number of related factors. A key driver will be the location of the green wall with regard to temperature, light levels and exposure to the elements. The function of the wall will also determine the plants required. High impact feature walls typically require plants with abundant foliage and brightly coloured flowers. Walls designed to improve air quality should be planted with species that absorb dust and toxins.
Light levels (sun or shade) may demand a selection of plants able to cope with specific conditions. Indoor walls may require additional artificial light to support plant growth. Though not essential it can also be beneficial to select plants that require similar levels of irrigation to reduce the complexity of the irrigation system required.
Expectations for overall aesthetics, the speed of coverage and initial growth need to be considered. Some systems (especially façades) may require several years’ growth before achieving the desired visual impact.
A reliable watering system is essential for a successful long-term installation. Walls have failed in the pass due to inadequate irrigation solutions. The complexity required will vary from basic timer controlled dripper lines to computer controlled systems with automatic moisture monitoring, leakage detection and pressure regulation.
Green façades generally use climbers that grow from the ground or in containers. Location will determine level of irrigation required and any additional nutrient supply. Plants will typically be hardy and robust species able to support their growth with minimal intervention so will generally only require a relatively simple irrigation system.
Modular living wall techniques require more reliable irrigation and generally demand a fairly sophisticated automated solution which will depend on temperature, exposure and plant-type. Vegetation used will also determine the level of nutrients required and how frequently these need to be applied.
In the UK many plants become dormant during the winter and it may be necessary to reduce or even shut-down irrigation systems in some situations. It is important to monitor and adjust irrigation levels regularly on all installations.
In addition to the obvious height challenges, there can often be a number of access issues when installing and subsequently maintaining green walls. Ease of access to the structure may even dictate the type of system chosen. In general it is far better to plan green wall installations during the original design of buildings, rather than rely on retrofitting afterwards.
Green façades generally only require access to the base of the wall, especially once growth has been established and initial coverage achieved, though it is likely some periodic pruning will still be required. Other systems require regular access to the complete structure for maintenance and monitoring. Often staging, platforms or even abseiling experts are required to provide safe and effective access for maintenance tasks.
Maintenance and services
The maintenance of a green wall is key to its success and needs to be seriously considered at the start of any project. Often a controversial subject the long term maintenance of a wall can become the most expensive and labour intensive element. Green walls are living organisms and as such require adequate support and nurturing to survive. With many solutions this can be minimal but must suit the application, the technique used and the plants involved.
The level of maintenance will include need for plant pruning, feeding and replacement. Some systems will also need monitoring to ensure structural elements remain secure and do not deteriorate, e.g. correct tension in wire-rope systems.
To maximise the longevity of a green wall it is important to highlight costs and requirements early. Clients must be made aware of their responsibilities to ensure long term project success.
The provision of services such as power and water are essential to many green wall systems and it is important to ensure these can be supplied within the scope of the project’s budget.
Policies, standards & incentives
Increasingly councils and planning authorities are looking at encouraging the inclusion of greenfrastructure in new developments and many Local Development Framework (LDF) policies are being modified to reflect these changes. Though no standards or certification processes are currently in place for green wall installations, there is a movement amongst industry experts to address this gap through the development of a trade association for green wall providers.
In the meantime the most common specifications adopted in the UK for sustainable buildings is the BREEAM environmental assessment method and rating system for buildings (www.breeam.org). Though no green wall specific measures or ratings are currently in effect, the ratings system can be applied to green walls in two main areas:
1. The materials used in construction of green wall system.
2. Improvements in biodiversity offered by the new/addition of plant species in the area.