Greening our grey cities: here’s how green roofs and walls can flourish in Australia



Melbourne Sky Park, between the CBD grid and Docklands precinct.
Oculus, used with permission, Author provided

Nicholas Williams, University of Melbourne; Cathy Oke, University of Melbourne, and Leisa Sargent, UNSW

Tomorrow is the first World Green Roof Day. Cities around the world will celebrate the well-documented environmental, economic and social benefits of green roofs. New ground-level green spaces are difficult to create in high-density urban areas. As a result, other forms of city greening – green roofs, green walls and vegetated facades – are increasingly popular.

Being able to grow plants up and on top of buildings combines grey infrastructure with green infrastructure. Unfortunately, most Australian cities are lagging behind many international counterparts in this aspect of urban greening.

Growing Up green roof by Bent Architecture on the top of 131 Queen Street, Melbourne.
University of Melbourne, Author provided



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Roadmap outlines key steps

Green wall by Junglefy at One Central Park, Sydney.
John Rayner, used with permission, Author provided

To explore how to increase the uptake of engineered green infrastructure we ran appreciative inquiry summits in Sydney and Melbourne. More than 60 representatives from the building and horticultural industries, local and state governments and universities attended. They worked together to create a positive vision for greener Australian cities using green roofs, walls and facades.

Participants identified key actions to achieve this goal. These are compiled in the Roadmap for green roofs, walls and facades in Australia’s urban landscapes 2020-2030. The newly released report sets out how to achieve a flourishing green infrastructure industry and more liveable, green, climate-adapted Australian cities.

There is a significant amount of Australian-specific information on the benefits, value and construction requirements of green roofs, walls and facades. Sharing this knowledge is essential for accelerating advances and bringing people up to speed quickly. A key recommendation was establishing a cloud-based knowledge hub and accompanying programs.

Biodiversity Green Roof by Junglefy at Yerrabingin Indigenous Rooftop Farm in South Eveleigh, Sydney.
Junglefy, used with permission, Author provided

It’s also about job growth

Green roofs, walls and facades require a diverse mix of professions and trades to build them. As the sector grows, many jobs will be created.

Medibank Private green wall by Fytogreen at 720 Bourke Street, Melbourne.
John Rayner, used with permission, Author provided

Changes to government policies and inclusion in economic recovery programs are key to this. For example, in Toronto a 2009 bylaw made green roofs mandatory on new buildings with floor areas greater than 2,000 square metres. That change is estimated to have created more than 1,600 jobs in their construction and 25 jobs a year in maintenance.

Education and training programs will be needed to upskill the new workforce. The National Skills Standards for Green Walls and Rooftop Gardens is a welcome vocational training initiative. In addition, university engineering, design and planning graduates require greater expertise in both policy and implementation, backed up by continuing professional development programs.

Research green roof at the University of Melbourne Burnley campus.
Nicholas Williams, Author provided



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Government leadership makes a difference

Strong government leadership is a feature of countries and cities with a rapid uptake of green roofs, walls and facades. They have clear policies and strategies, established funding mechanisms and good co-ordination among all levels of government.

Victorian Parliament Members Annexe green roof.
Rachael Bathgate, used with permission, Author provided

A national transition to more sustainable cities that incorporates systematic job-making is desirable. It could be achieved through new federal government City Deals focused on stimulating the green economy.

The European Union has already proposed fiscal recovery packages along these lines. Economists have identified policies with high potential for both economic multiplier effects and climate impact.




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Cities that combine incentives with regulation have higher rates of green infrastructure installation. Education and advocacy to ensure standards of design, installation and maintenance further improve these rates. Importantly, tailored policies can produce green roofs, walls and facades that deal with specific impacts of urbanisation, such as stormwater runoff in flood-prone catchments.

Green wall by Fytogreen at 1 Bligh Street, Sydney CBD.
John Rayner, used with permission, Author provided

The City of Melbourne has adopted this approach. Its Green Our City Strategic Action Plan identified the benefits of requiring new buildings to include green infrastructure via a planning scheme amendment. The amendment is yet to be approved. However, the city’s Urban Forest Fund is providing incentives for projects.

In addition, the council has released an Australian-first online Green Factor Tool to measure and improve vegetation cover on new developments. Developers have been asked to voluntarily submit a green factor scorecard with building planning applications. This is expected to increase greening in the private realm.

Crisis also creates opportunities

The upheavals in how we live and work caused by COVID-19 also provide opportunities. It’s a chance for developers and building managers to rethink apartment and office building design, with health and well-being in mind. The benefits of green roofs for the cognitive functioning and well-being of employees are already well documented.




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During the pandemic we have seen high demand for urban green space and nature. Rooftop and podium-level green roofs can help meet this public need. If next to lunch rooms, these spaces may help workers feel safer in communal areas.

Breathing Wall by Junglefy at 485 La Trobe Street, Melbourne.
Junglefy, used with permission, Author provided

A business tax incentive for retrofits of this type would also help to stimulate the construction industry.

Australian cities are already experiencing hotter days, more intense storms and flooding. Creating more green roofs, walls and facades is an important way to respond to climate change and biodiversity impacts. At the same time, these actions create engaging and restorative outdoor spaces for workers and residents. The new roadmap provides a bold but achievable path towards a more sustainable and liveable future.The Conversation

Nicholas Williams, Associate Professor in Urban Ecology and Urban Horticulture, University of Melbourne; Cathy Oke, Melbourne Enterprise Senior Fellow in Informed Cities, Connected Cities Lab, University of Melbourne, and Leisa Sargent, Senior Deputy Dean, UNSW Business School, Co-DVC Equity, Diversity and Inclusion, UNSW

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Climate explained: how white roofs help to reflect the sun’s heat



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Nilesh Bakshi, Te Herenga Waka — Victoria University of Wellington and Maibritt Pedersen Zari, Te Herenga Waka — Victoria University of Wellington

Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.

If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz

Does the white roof concept really work? If so, is it suitable for New Zealand conditions?

Generally, white materials reflect more light than dark ones, and this is also true for buildings and infrastructure. The outside and roof of a building soak up the heat from the sun, but if they are made of materials and finishes in lighter or white colours, this can minimise this solar absorption.

During the warmer part of the year, this can keep the temperature inside the building cooler. This is especially important for building and construction materials such as concrete, stone and asphalt, which store and re-radiate heat.




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On a hot day, a white roof can keep the temperature cooler inside the building.
from http://www.shutterstock.com

A New Zealand study tested near-identical buildings in Auckland with either a red or white roof. It found that even in Auckland’s temperate climate, white roofs reduced the need for air conditioning during hotter periods, without reducing comfort during cooler seasons.

The study also identified several large-scale white-roof installations, including at Auckland International Airport, shopping centres and commercial buildings, but the effect was less clear.

This research suggests that there is potential for white-roof installations to significantly reduce the amount of energy needed to cool buildings. This would in turn reduce greenhouse gas emissions and also help us to adapt to rising temperatures.

It is difficult to quantify the impact for New Zealand’s housing stock because existing studies are mostly limited to larger commercial buildings. But research carried out so far suggests white roofs could be a viable approach to minimising the heat taken up by buildings during hotter parts of the year.

Cooling cities

White roofs can also help reduce the temperature of whole cities. Many city centres include large buildings made of concrete or other materials that collect and store solar heat during the day. In a phenomenon known as the “urban heat island” effect, city centres can often be several degrees warmer than the surrounding countryside.

When cities are hotter, they use more energy for cooling. This usually results in more greenhouse gas emissions, due in part to the energy consumed, and contributes further to climate change.

New Zealand is different because our land mass has a maximum width of 400 kilometres. This means that unlike many urban islands on the African, Asian or American continents, New Zealand’s city centres benefit from the cooling effects of being near the ocean.




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There are many international studies showing white roofs are effective in mitigating the urban heat island effect in densely populated cities. But there is little evidence that using white roofs in New Zealand cities could result in significant energy reductions.

A growing number of studies suggest making the surfaces of buildings and infrastructure more light reflecting could significantly lower extreme temperatures, particularly during heat waves, not just in cities but in rural areas as well. A recent study shows strategic replacement of dark surfaces with white could lower heatwave maximum temperatures by 2℃ or more, in a range of locations.

But studies have also identified some practical limitations and potential side effects, including the possibility of reduced evaporation and rainfall in urban areas in drier climates.

In conclusion, white roofs could be a good idea for New Zealand to keep homes and cities slightly cooler. As temperatures continue to rise, this could reduce the energy needed for cooling. We should consider this option more often, particularly for commercial-scale buildings made of heat-retaining materials in larger cities.The Conversation

Nilesh Bakshi, Lecturer, Te Herenga Waka — Victoria University of Wellington and Maibritt Pedersen Zari, Senior Lecturer in Sustainable Architecture, Te Herenga Waka — Victoria University of Wellington

This article is republished from The Conversation under a Creative Commons license. Read the original article.