The effectiveness of climate positive design measures (mitigation and adaptation) is dependent on how closely the intent of the designed landscape aligns with the project as-built.

Post Occupancy Evaluation (POE) in landscape architecture gives us the opportunity to assess the effectiveness of design strategies related to material use, water use, energy use, carbon sequestration, urban heat, drainage infrastructure, species resilience, and biodiversity.

However, POE in landscape architecture is not yet common practice, so we are missing the opportunity to complete a “virtuous circle of learning” ¹.

The intent of POE in the designed environment is to generate knowledge to help designers close the performance gap between the designed project intentions and actual measured outcomes. POE is an opportunity to understand what works well, what hasn’t been successful, and any unintended consequences for the site or adjacent areas.

Typically, an evaluation covers three areas; social evaluation of spaces to understand if they meet user needs; technical evaluation of performance; and process evaluation of the effectiveness of project delivery ².

It is recommended that POE is undertaken a number of times over the lifetime of the development ². POE creates a feedback loop that informs remediation measures as well the design of future projects.

Closing the performance gap is critical to achieving our climate positive design objectives. If the projects’ as-built aren’t meeting the designed performance requirements, for example canopy coverage, the implication is that we are not mitigating climate change risks to the required targets. Climate positive design refers to projects that sequester more greenhouse gases that they emit over the project lifespan. The importance of learning from successes and failures is a universal principle of climate responsive design ³.

Aboriginal and Torres Strait Islander people have long demonstrated the ability to learn from and embed experience related to changing environments in Traditional Ecological Knowledge (TEK). Indigenous peoples are using TEK and creating new knowledge based on centuries-old traditions of knowledge maintenance ⁴. As with many aspects of ecological responsive design, it is indigenous people who provide enduring examples of best practice.

How do we close the performance gap?

Closing the performance gap refers to reducing the difference between anticipated design outcomes and actual results. This can relate to comparing the modelled performance of energy and water use at design stage against actual measured performance in operation.

POE can also help identify poor construction, inappropriate detailing or material specification, and unintended use or behaviour. In this way, POE helps support the project’s climate positive design objectives, for example reduction in water use or increased longevity of materials. The impact of poor detailing or material specification is a short design life, which ultimately increases carbon emissions by requiring material replacement.

In landscape architecture, a critical area of performance relates to urban green infrastructure and ecosystem health. Landscapes are ecosystems which interact with the environment at a series of scales and must therefore be understood and evaluated at different scales. Key questions in POE are whether the project fulfills the needs of the user, performs as anticipated, causes unintended consequences to the site or adjacent systems, and is likely to achieve the anticipated design life. A baseline study of existing site conditions, and a framework of performance requirements is needed to provide the structure for the POE.

What does performance mean for plants?

The climate positive performance objectives of Urban Green Infrastructure (UGI) include carbon sequestration, biodiversity enhancement, urban heat mitigation through shading and transpiration, contributing to active travel, human wellbeing, and urban liveability. All of these factors rely on maintaining plant health. Therefore, in order to achieve our climate positive objectives for UGI, we need to monitor and ensure the health of urban ecosystems.

As an example, let’s consider carbon sequestration. Carbon sequestration can be achieved through the soil and in plant biomass. Soil sequestration is impacted by photosynthetic coverage (plant cover), species diversity, root biomass, and deadfall accumulation ⁵. In trees, carbon dioxide is sequestered into woody biomass through leaves. Larger trees with more leaf canopy can sequester more carbon. Carbon sequestration is dependent on ecosystem integrity which includes characteristics such as biodiversity, vegetation biomass, and nutrient cycling. Ecosystem integrity is threatened by bushfire, drought, pest and pathogen incursion, and the accumulation of adjacent land use degradation that may impact water quality, erosion, biodiversity ^{6 5,7}. Higher ecosystem integrity, particularly biodiversity, tends to limit pest and pathogen spread ⁶, therefore it is essential to maintain ecosystem integrity. Achieving our carbon sequestration targets is directly linked to maintaining ecosystem integrity.

There is a series of parameters we need to assess and monitor that will influence whether the landscape as designed achieves targeted ecosystem performance requirements. Variables include plant condition, water quality, soil health, soil moisture, nuisance lighting, loss of connecting corridors, weed/pest incursion, fertilizer use, plant position and grouping, fauna movement, and insect occurrence. Observations need to be further interrogated in order to understand the cause of any ill-health. For example, plant cover and condition might be related to trampling due to pedestrian desire lines.

Standards Australia’s Urban Green Infrastructure Handbook sets up the expectation that in order to achieve urban green infrastructure (UGI) targets, UGI health and functionality must be monitored and managed over time ⁸. Monitoring is expected to be carried out to assess survival rates, growth, and benchmark performance on an incremental basis against clearly defined objectives.

POE tools for landscape

Landscape architects can use a series of tools including surveys, interviews, visual assessments, soil testing, thermography, temperature/air velocity/humidity sensors, water/energy metering, and light/noise meters to evaluation landscape performance. Engaging with traditional owners, and collaborating with botanists, ecologists, and environmental scientists is also recommended. The Landscape Architecture Foundation’s Guidebook ⁹ provides a comprehensive framework of performance metrics and methods for evaluating environmental, social and economic performance. The Gehl Institute’s Public Life Tools is another useful resource for evaluation the performance of public open space.

The criticism of POE has been that they are prepared largely by academics and not widely disseminated in design practice ¹⁰, which reduces their potential impact  ^{1 9}. Sharing the lessons learnt in POE will amplify the value of POE as a climate positive design strategy. Setting ambitious targets for climate positive design is essential, but ensuring they are met is critical.

References

1. Post Occupancy Evaluation and Building Performance Evaluation Primer. https://www.architecture.com/knowledge-and-resources/resources-landing-page/post-occupancy-evaluation (2016).
2. Dowson, M., Riebel, M. & Gill, Z. Chobham Manor Phase 1 Post Occupancy Evaluation Survey. https://www.hawkinsbrown.com/sub-services/post-occupancy-evaluation/ (2022).
3. Clegg, P. & Sanderman, I. Manifestor for Climate Responsive Design. https://www.feildenfoundation.org.uk/manifesto-for-climate-responsive-de (2019).
4. Nursey-Bray, M., Palmer, R., Chischilly, A. M., Rist, P. & Yin, L. Old Ways for New Days: Indigenous Survival and Agency in Climate Changed Times. (Springer, 2022).
5. Tian, Q. et al. Plant diversity drives soil carbon sequestration: evidence from 150 years of vegetation restoration in the temperate zone. Front. Plant Sci. 14, (2023).
6. Rogers, B. M. et al. Using ecosystem integrity to maximize climate mitigation and minimize risk in international forest policy. Front. For. Glob. Change 5, (2022).
7. Quirion, B. R. et al. Insect and Disease Disturbances Correlate With Reduced Carbon Sequestration in Forests of the Contiguous United States. Front. For. Glob. Change 4, (2021).
8. SA HB 214:2023 Urban Green Infrastructure – Planning and decision framework. (2023).
9. Canfield, J., Yang, B. & Whitlow, H. Evaluating Landscape Performance: A Guidebook for Metrics and Methods Selection. https://www.landscapeperformance.org/guide-to-evaluate-performance (2018).
10. Whittem, V. & Roetzel, A. Learning from built projects – sources of post occupancy feedback used by architects in Victoria, Australia. Intell. Build. Int. 13, 311–326 (2021).

By Jen Lorimar-Shanks