As our cities become increasingly denser, the available area for living outside, whether it be public or private open space, becomes more precious.
We are surrounded by more and more concrete, glass and steel. Ground level green space is also being lost as a consequence of medium and high density developments.
Governments try to counter this through their planning regulations which often dictate that developments provide a required amount of ground level open space. However, overall the result is a nett reduction in green space in our cities.
The planning regulations also try to improve the quality of our urban spaces by mandating a stepping back of buildings from the street frontages. This can contribute to improved streetscapes, but results in a reduction of lettable floor area as the levels go up.
People are intrinsically predisposed to surround themselves with living plants. Biophilia is a well-studied phenomenon that has been demonstrated to improve human well-being. When people move into a new development, they often express this desire by cramming in as many pot plants as they can to fill their outdoor terrace spaces.
This is not only the case for many multi-storey residential developments. There is also a growing trend towards including greenery throughout new commercial workplaces and retail spaces.
Unfortunately, unless the building owner and/or tenants are committed to tending these sky gardens, the plants invariably die. Like some on-ground landscapes, greenery at height that is ad hoc and not integrated into the form and fabric of the urban environment, if it is reliant on manual irrigation, is unlikely to survive in the medium to long term, especially given the harsh Australian climate. All too often the living green is replaced with dead brown and the pots eventually get removed.
But what if the development was to integrate these features into the project from the beginning?
Rather than being an afterthought, the terrace garden could be an integral part of the living space. Much like the best of all good architectural design, integration of indoor and outdoor space is possible at height.
The roof terraces resulting from the planning scheme set back requirement, rather than being windblown, hot and hard paved spaces, could be lush garden rooms that increase the property value.
Rather than having a barren balcony terrace around the lunchroom-kitchen of an office development that no one ever visits, it could be a soft and comfortable space that gets used every day.
Creating these living green spaces need not be difficult or expensive and provided they are designed well and integrated into the overall project, they will be relatively low maintenance. As more and more of these projects are successfully realised, the technology and methods of establishing greenery at height improve to ensure success.
The greenery, as well as increasing property value, also provides many other benefits.
Some of these are tangible, such as the reduced temperatures caused by the shading and evapotranspiration effects of plants. Living systems also contribute to management of storm water by retaining water on site and removing contaminants.
Other advantages are less tangible, such as mental health benefits of being close to plants.
The vertical surfaces of buildings can also be integrated with greening to extend these benefits. Green walls that spread plants over substantial vertical surface areas can look spectacular, especially when combined with other roof garden elements.
Facades consisting of front window glazing can also support living things. A green façade is an efficient way of providing extensive areas of vertical greenery at relatively low cost, especially when compared to other feature architectural façade expressions and glazed curtain walls.
There are many climbing plants that will vigorously twine up a cable or mesh structure. Not only does this vertical garden provide exquisite visual interest, it also provides a cooling benefit to the internal spaces, reducing energy costs for summer air conditioning.
Recently in Australia, there has been many advances in the technical understanding and policy develop that encourage more widespread uptake of these approaches.
For example the City of Sydney has recently produced a Green Roofs and Walls policy. Further to this, the group of local councils contributing to the Inner Melbourne Action Plan has produced the Growing Green Guide for which provides the following advice:
Property developers should consider the importance to them of building sustainability ratings schemes as they commission a design for a green roof, wall or facade. For instance:
- Public buildings can obtain Green Star points for green roofs, and other buildings have an indirect way of achieving points under the category of ‘land use and ecology’, if the installation is designed with native plant species and a focus on ecological value
- Under the National Australian Built Environment Rating Scheme, green roofs, walls and facades may be able to contribute to ratings in categories of thermal comfort and acoustic comfort
- In the green building certification program, ‘The Living Building Challenge’, green roofs, walls and facades may be able to contribute to building thermal performance, energy efficiency, and water re-use objectives
- NatHERS (Nationwide House Energy Rating Scheme) looks at the energy efficiency of new residential developments, and green roofs, walls or facades can be designed to improve efficiency.
Unfortunately, the many benefits of these features although well understood in principle, have not been quantifiably researched to the point where they can be easily worked into a business case for a development.
We know that greenery cools buildings, but we can’t yet definitively include this contribution in a BCA compliance for Section J, or use this cooling function the gain Green Star points.
Furthermore, although we know that a green roof will reduce storm water runoff volumes and improve water quality, we don’t know empirically how much.
Increasingly we are seeing a gain in momentum and uptake of living architecture in the projects we work on, which will undoubtedly continue as we respond the challenges of our urban environments.