The New York High Line

There is now no doubt most people will live in cities for the foreseeable future. The wealth benefits of collaboration and connection on economic growth, opportunity and innovation underpin this inexorable shift, particularly in an economic structure dominated by the service industries.

As cities become larger, they become denser and with density comes closely packed built form. As architects and urban designers, we are well aware of the benefits of daylight and fresh air to health. These principles inform public policy, with one of the most complete examples of policy response being SEPP 65 in New South Wales.

Given the emerging evidence base with respect to the health benefits from access to green views and spaces, the current policy response is incomplete and requires re-evaluation in order to deliver healthier outcomes, particularly in dense urban contexts.

A case study is presented in order to illustrate that, as there is recognised commercial value in views, imaginative urban context interventions are possible that can boost both social and economic wealth and lead to a more sustainable and resilient urban fabric, with very minor public policy intervention.

Inspiration and context

Vitamin G, where G stands for the green space around us – research has demonstrated that mere exposure to views of nature can improve people’s health and well-being by providing restoration from stress and mental fatigue.”

The benefits from the body of research into the effects of Vitamin G include positive impacts on immune system resilience, with implications for public health expenditure and labour productivity.

The main thrust of this paper was inspired by a talk by Pritzker Prize winner Wang Shu at the 2012 Australian Institute of Architects’ conference where he argued impressively that landscape was the key to architecture.

His presentation began with a philosophical statement of how far his home city of Hangzhou has moved from traditional Chinese values of living within nature illustrated by the image at the top of the page; built form integrated into the landscape.

Perhaps his most compelling contrast was one of aerial views. The message from the photograph at the right is one of zero Green, and particularly above the ground plane, looking at the roof zones. The image above it shows a built form integrated with, and complementary to, the natural landscape.

Given the evidence emerging with respect to the positive effects of landscape on health (and the negative impacts of no landscape), the overarching lesson seems clear: landscape is the key to urban design as well as architecture.

In a strategic sense and from an urban planning context, urban design is now covering the ground plane relatively well, and there is growing recognition of a need to increase parklands and open space in dense urban areas.

However, above 25 metres, looking over other buildings and in densely packed urban form where buildings look across at each other, the effect is zero Vitamin G (no access to or views of landscape). It is here that the opportunities lie.

The above image is a scene repeated across the world in most CBDs, it is not just Hangzhou, and presents an opportunity for urban design policy and practice. The implication of the body of Vitamin G research evidence is that this urban context, if left unmitigated, is leading to sub-optimal health outcomes. In parallel, we are seeing a continual drive towards high performance cultures in organisations and higher productivity across our economies.

Disturbingly, a recent paper by Jane-Frances Kelly and Paul Donegan of the Grattan Institute has pointed out: “Knowledge-intensive businesses – which are the most productive today – tend to cluster and thrive in the centres of large cities.”

The tension between leafy suburban office park and relatively grim urban CBD locations begins to come into a better focus in this context. In particular, worker mobility and the emergence of distributed models for organisations leveraging new technologies are challenging this dialogue and may be impacting relative values at the margin.

But the lesson is clear, there are strong economic drivers that force people together into dense urban environments and the evidence points to sub-optimal health and productivity outcomes from the environments that we are currently producing.

The tenant representative market is particularly good at identifying weaknesses in leasehold property on behalf of the potential lessee; the Vitamin G equation is a fertile field for the negotiations. A recent article by Carolyn Cummins in the Sydney Morning Herald contains the following quote from JLL’s manager of office leasing Christopher Selman commenting on tenant interest for a rooftop garden space:

“Tenants are attracted to the funky outdoor common area… it’s this element that… appealed to aspiring youthful companies, who are looking to attract and retain the best staff.”

We are also seeing a sharp increase in demand for inner city living. I was dismayed to hear a property colleague recently excuse the provision of dark units at the bottom of a building with a view across a relatively narrow street as acceptable because “lower value units are always required”.

In the context of this discussion, where the evidence suggests less positive health outcomes are likely from this environment as from better placed units, this comment further illustrates a need for consideration of public policy intervention to raise the minimum standard.

The Initial Study

It is in the context of zero G environments that three years ago I persuaded a colleague, Joseph Jerome, to assist in developing a proposal for the Plaza Building in Australia Square in Sydney that would explore these issues.

Australia Square is one of Sydney’s iconic developments. Designed by Harry Seidler, it makes an enormous contribution to Sydney’s urban structure, by breaking it apart and creating a much loved, sunny and very active plaza space connecting George and Pitt streets (above).

The Plaza building on the eastern Pitt Street frontage is raised above the street extending the plaza to the street frontage. In terms of its aesthetic it is emblematic of its time, rigorous and robust; a complement to the soft curve of the circular tower opposite. In today’s context, it presents a formidable and alienating façade, softened by very large plane trees in the streets and plaza.

Our aim for the initial study was to explore the aesthetic of application of a green wall to this dramatically orthogonal façade and identify the costs of such an intervention as a base for further consideration.

The scheme imagined cladding three of the four facades with a green wall in an integrated zero water and energy schema, as a part of a full building upgrade, including a re-cladding (ignoring for the time being the heritage significance of the building and the sun shades).

Our first insight was quite counterintuitive; that it was better to impose an organic super pattern to the planting arrangement over the window/spandrel/column grid than to simply cover the non-window areas. This allowed for less investment in the planting while delivering a more compelling image.

In addition, diagonal flowing patterning of planting on the fully covered end façade further added life and dynamism to the composition. This latter characteristic is also evident in Patrick Blanc’s work at Central Park One.

We were very fortunate to have some assistance from Rider Levitt Bucknall, who very kindly provided a budget estimate for the works. This identified costs of approximately $8 million for the green walls only.

While an attractive and interesting intervention, and one that would have created significant interest in the property, the second insight was that it was difficult to see how to justify the $8 million capital cost and ongoing maintenance without evidence of value uplift significantly in excess of $10 million.

In interrogating this value equation two issues arise. Firstly the benefit is limited to the floor space in adjacent buildings directly affected, which is in the broadest sense the levels directly opposite and even then only to a depth of 10-12 metres.

Further, the value does not necessarily accrue to the Plaza Building itself as the landscaping is not really visible from within the building.

Secondly, the value accrues to many properties adjacent to the intervention who, given different ownerships, would not contribute to the renovation.

The value equation can be summarised as the potential capitalised rental uplift for spaces with views of the green intervention. For this intervention, these areas are quite limited within the property.

Putting values on the uplift value is done in this study to illustrate the challenges of economic modelling such an intervention and as a guide to the relative performance of the two options presented. It is aimed at indicating potential for further study. However, it is based on accepted market value structures in that views of, and access to, landscape will elevate the value of the space. In this case we might attribute an uplift of perhaps 50 per cent of the difference between current rental yield and the next pricing level within the building (for example, from mid-rise to high rise).

The value uplift would then be assessed as a proportion of the value uplift realised. Let’s assume that this is about 50 per cent of $60 a square metre a year over what is likely to be approximately 8000 sq m, which equates to $240,000 a year. Capitalised at 7.5 per cent this would be $3.2 million and thus well short of the $10 million target. Clearly further income generation would be required to create a feasible economic model.

The Next Iteration

Upon further optioneering, a strategy emerged that has the potential to not only add value through all the office space in Tower and Plaza but also in adjacent buildings. The proposal creates a framework that could also allow the owner of Plaza to leverage the value provided by visual and physical access to green spaces.

The revised proposal envisages less, and higher, green wall additions but much greater intervention at the roof level, a sky park, and involves some interruption of the other base building works with bridge access across to the park.

The value equation becomes much more attractive. Although costs would move to around $12 million, average uplift at $15/sq m/year across all the buildings (say 100,000 sq m) would generate $1.5 million/year. Capitalised at 7.5 per cent, this is $20 million, potentially enough to build a coalition of interest across the building and air rights owners concerned (which will include Council).

The additional potential of a link to the Radisson Hotel provides further potential uplift for all properties. Taking the idea even further, it should be possible to add apartments above two of the buildings to the south that would create high value living spaces with a northerly aspect and access to, as well as views onto, the park.

While the numbers in this study are essentially notional, bridge connected sky parks (perhaps combined with green wall interventions) in existing or new urban contexts look to offer significant value uplift and resilience to the property owners and the city itself.

Urban design policy implications

Bridge links in city centres have only been seen as beneficial in circumstances where there are large flows of people that need to transgress busy roads, such as in integrated malls across city streets and mass transit connections. The immediate policy interventions required to facilitate a bridge linked sky park proposal look to be quite minor:

1. Identify opportunity sites, actively promote exploration of sky park interventions and facilitate the processing of submissions

There are many areas within CBDs where these types of interventions can add to the triple bottom line of all stakeholders. No single body has all the best ideas.

The city could consider a consultation and imagineering process to help identify and prioritise key sites. It will also need to be open to proposals and to develop a tailored application framework to address these.

For example, this could require a submission to have the consent of the major adjacent landowners, excluding council in the first instance. The evidence base from the first projects would also inform the application procedures.

2. Promote the design of bridges that mitigate shadowing effects

Bridges designed to brighten the street below would go some way to mitigating the shading effects. It is here that the design excellence pathway championed by the City of Sydney could be further deployed.

3. Create a learning framework to generate an evidence base

The city’s ownership of most of the air rights places it in a pivotal position in the establishment of a commercially successful model. Recognition of the uncertainty around the quantification of value uplift and an approach built on developing an evidence base that can then inform further interventions would seem the most appropriate policy stance for the initial projects, and one that can then assist in refining detailed regulatory and commercial terms.


Strategies to leverage the implications of the evidence demonstrating positive physiological benefits of Vitamin G are emerging that can be very exciting for both existing and new urban form above 25 metres. In particular, accessible sky parks have the potential to enrich dense urban context in both social and economic terms.

There is also the potential for acceleration of adoption of these interventions through development of suitable urban policy and regulatory settings.

“Delivering connected, light filled green urban form above 25 metres can deliver sustainable value and greater amenity, health and productivity in our densely packed cities into the future.”

Anthony Thorp is director, architecture at Reid Campbell. This is a presentation he gave at the 7th International Urban Design Conference.