By Michael Casey
Today, more than ever, society is placing a greater importance on greenspaces and the integration of them in both private and public environments. To better understand the importance we place on these spaces, we need not look any further than the outpouring of emotion when public parklands and playgrounds were closed during lockdowns, or when we celebrated our own personal greenspaces in and around our homes while we worked and were educated from home.
With many reasons to turn to greenspaces, whether it be for mental well-being, environmental purposes or aesthetics, we can all agree that the addition of green infrastructure into our built environment is a decision that will benefit different cohorts of people, for many different reasons and in a myriad of ways. One way of identifying these benefits is through identifying and understanding the return on investment (ROI) that these spaces provide. By using measurement and other methods to assess ROI, this provides industry, buyers/sellers/owners and users, with a greater appreciation and education of green installations.
Green infrastructure is not too dissimilar to other methods of building and upfront costs can be significant in some cases. Green infrastructure in the forms of walls and roofs benefit from economies of scale; the more you buy, the cheaper the cost per unit and in most cases, the higher the overall return. In valuing green infrastructure, this can be performed through methods such as ‘hedonic pricing’, which assumes the environmental characteristics and other property features that are reflected in property prices, and ‘avoided costs’ which examines the marginal costs of providing an equivalent service in another way. To understand how we will evaluate these, this requires us to start defining benefits and the key criteria to which value is assessed.
Public and private benefits is one form of categorising value and therefore to understand ROI. Public benefits can be on a neighbourhood or municipal scale and tend to benefit grey infrastructure, environments and communities. Private benefits can be categorised based on building or ownership scale and tend to benefit operations, lifecycle costing and ROI evaluations.
Public benefits can include storm water management, urban heat island management, employment opportunities and air quality. These benefits are usually valued by government/municipalities and companies dealing in infrastructure directly attached to green infrastructure builds. In a private context, typically these benefits are not valued to the same extent. The exception being when a house/property is protected in flood prone areas by green infrastructure installations, or cooled by trees and plants installed in areas in built up environments that lack green spaces.
The following four public benefit examples of green infrastructure will assist to paint a clearer picture in terms of true value and ROI.
Stormwater management through better installations of rain gardens, bio-retention ponds, green roofs will improve the quality of stormwater running into the sewer or creeks. It will place less stress on this existing infrastructure which in turn reduces and mitigates peak flows. This lessening of water flows can then reduce flooding, damage to existing stormwater systems and damage to roads and pavements to name a few.
Urban Heat Island effect can be reduced not just by better choices made with building materials but through the use of greenery in and around these buildings and cities. Using greenery such as tree plantings, green roofs, and walls, and facades, can help in reducing ambient air temperature, reduce local pollution and improve ambient humidity levels. These green installations work at reducing associated health costs, municipal power costs and improving recreational spaces.
Employment opportunities exist when new infrastructure is implemented. The professions involved in green infrastructure are varied, with a typical green wall requiring plants from a nursery, installers, irrigation experts, companies to supply the products, and then maintenance staff to manage and keep the asset in optimal condition. The enhanced local economic activity and improved tax revenue should be seen as another benefit that can filter back into communities.
Air quality is a benefit that can also mitigate air temperature extremes, capture airborne particulates and filter volatile organic compounds. These benefits then relate back to reducing associated health care costs, through to improving infrastructure filtration systems. Rainwater captured on green roofs and even non-planted roofs that are surrounded by plant material, will be filtered of particulates that sometimes obstruct filtration systems in water recycling systems. As plants are used in green walls, facades and roofs, the benefit from increasing plant biomass on buildings has the ability to create more aesthetically pleasing surrounds, both on the building and for people in surrounding structures which can also result in reduced worker absenteeism. Plant mass can manage temperatures on buildings (thermal mass), and increase biodiversity while stabilising local ecosystems.
There is a lot of cross-over of benefits across private and public valuation areas, however some benefits can be more exclusive to the private side in terms of increased property value, improved roof and wall durability, and agricultural opportunities and social benefits.These benefits would, for example, be more widely experienced by property owners for example.
The specialised planning and programming of either creating or enhancing amenity spaces, highlights the multiple ways green infrastructure can be implemented into the many different sectors of our built environment, whether that be green walls, facades or roofs. This therefore leads to an increased likelihood of saleable spaces, increased property value, higher rental returns, and adding to supplementary income potentials. In real estate terms for example, this can help boost marketing efforts and contribute to overall property desirability and viability.
Green walls indoors, for example, will allow for the creation or enhancement of amenity spaces by repurposing areas that may have never been used to their full potential. These spaces create new environments for people to meet, socialise and congregate. For building owners, this maximises the spaces that are used and can then in turn be valued either through higher rental and sales returns, or supplementary income through short term renting of spaces such as cafes or food and coffee carts.
Green roofs can provide protection from environmental stresses and storm related activities such as extreme hail events. They also work on reducing the thermal flux which in turn equates to better temperature levels inside the building, and therefore reducing requirements for mechanical cooling and heating.
To apply costs to a project and then allocate budgets to its management and maintenance is better addressed when the designer and potential asset owner both understand not only the aesthetic values but also where their ROI will be derived from. This needs to occur at the earliest possible stage to ensure lifecycle benefits will outweigh upfront costs. The use of evaluation criteria and tools, and well-informed marketing content articulating and highlighting these benefits, will assist informing your next potential client/project, and why the installation of green infrastructure into their next project is a must!
Director of Evergreen Infrastructure and
National President of Australian Institute of Horticulture /
Board Member Interior Plantscape Australia.