A Holistic Sustainability Evaluation of Positive Energy Districts—Planetary Boundaries Framing the Transformation of Districts

Several initiatives in Europe aim for the clean energy transition in the built environment. The concept of Positive Energy Districts (PEDs) is advocated by energy policies and international working groups to accelerate the decarbonization of urban areas and promote the potential for scalability between cities. To be able to plan a district with a positive perspective of its attributes, it is mandatory to establish a new framework based on a list of key performance indicators (KPIs). Planetary boundaries (PB) define the boundaries of the “planetary playing field” for humanity if major human-induced environmental change on a global scale is to be avoided. Transgressing one or more PB could be highly damaging or even catastrophic due to the risk of crossing thresholds that trigger non-linear, abrupt environmental change within continental-to planetary-scale systems. Identifying the PB can therefore be used as an approach towards a new framework for PEDs based on a good understanding of the PB, i.e., towards an estimation of the safe space for human development. In this sense, it is interesting to study these PB in relation to district developments, namely, the new concept of PEDs.

In this paper, we address the need for a comprehensive understanding of the different aspects impacting the sustainability assessment of PEDs. In this sense, although highly advisable, an integrated and systemic approach to the sustainability assessment of PEDs has still not been consolidated and the main environmental, economic, and social pillars are usually treated as separate spheres with limited interlinked issues. To be able to build representative methodology for sustainability assessment of PEDs as well as define comparable, measurable, and reliable indicators specifically targeted for the district scale we take a closer look at the concept of PB to find out how this concept can help to establish a holistic sustainability evaluation of PEDs. There are three important key questions:

We collected data from literature on the PB concept and compared it with data collected from two PED concepts in Norway and Switzerland. Two PED concepts were analyzed relating to the methodology development and KPIs used to evaluate PEDs. These key aspects were used to analyze the PED framework (in the Norwegian and Swiss PED) relation to PB. As a result, those measures were identified which support the PB concept and those which should be analyzed further.

The 2000-W-Site (2000WS) is a new concept developed in Switzerland resulting in new forms of settlements (Haase 2021). It has gained a reputation for energy efficiency, renewable energies, and climate friendliness and reflects the values of a responsible society. The core idea of the 2000-W Site is an ongoing evaluation process of a site’s sustainability in terms of energy consumption and production in development, planning, implementation, and operations of the district. Certificates that document the status of development/sustainability progress are issued for a limited time period and must be renewed periodically. They are awarded in two stages: As a “site under development” until at least half of the total living space is in use, and after completion as a “site in operation”. The concept of a 2000WS takes an integrative view of the entire site rather than individual buildings by depicting the whole living environment. The subject areas of the criteria to evaluate 2000WS are shown in Table 2.

Already in 2008, the Norwegian Parliament decided that Norway should become “carbon neutral” by 2050 and recently Norway enhanced its nationally determined contribution under the Paris Agreement to reduce emissions by at least 50% and as much as 55% compared to 1990 levels by 2030 (Norwegian Ministry of Climate and Environment 2019).

There is no specific regulation for PEDs in general so the policy framework consists of different laws and regulations, guiding principles, white papers, and standards that influence the implementation of PEDs. While municipal goals are set on regional and urban scales through climate and energy plans, goals for buildings and blocks of buildings are set by their individual owners. Setting energy and emission goals at an intermediate level between city and buildings is a new approach in Norway and was mainly developed through the research center for Zero Emission Neighborhoods in Smart Cities, which is a frontrunner in developing this new research perspective in Norway. A Zero emission neighborhood aims to reduce its direct and indirect GHG emissions to zero over its lifespan. At the time of writing, a neighborhood is defined within the ZEN center as a group of interconnected buildings with associated infrastructure, located within a confined geographical area (Wiik et al. 2018) The ZEN definition is still under development but a framework of KPIs in six respective categories, namely, GHG emissions, energy, power/load, mobility, economy, and spatial qualities, is already in place (see Table 3).

Similar to the 2000WS concept, Norwegian districts will be assessed using these KPIs with a multi-criterial analysis. The results document the status of development towards zero emission neighborhoods and will help stakeholders involved to adapt plans, designs, and operating assets towards more sustainable patterns.

From the key performance indicators in PEDs (Tables 2 and 3), it is clear that two main indicators can be related to PB in PEDs. Firstly, to be able to mitigate further degradation of the climate system, it is mandatory to radically reduce GHG emissions. This not only includes reducing the energy consumption through conservation and efficiency but it also means switching to clean energy sources as well as reducing embodied carbon throughout supply chains and designing in general terms without waste generation.

PEDs as well as larger built environments also contribute to GHG emissions by embodied carbon in the built environment. Construction material use and its related embodied emissions as well as mobility both contribute to operational and embodied GHG emissions. IF green spaces are integrated into PEDs they can have a positive influence on reducing surface temperatures (urban heat island effect) and in addition on the operational energy and GHG emissions associated with cooling buildings and spaces in PEDs. In PED buildings, operational energy in both new builds and retrofits can be improved with efficient ventilation systems and passive and low temperature heating and cooling. In addition, efficient and natural lighting strategies and optimized building envelopes in co-design with efficient appliances have shown the potential to reduce operational energy. Embodied GHG emissions on the other hand can be minimized by reducing material use and choosing nature-based materials and circular processes. In PED, operating performance can be further improved with design considerations and innovation, and material demand can be reduced through increased efficiency. This requires that materials must be optimized throughout their lifecycle to reduce carbon in terms of their origin, extraction, processing and end of life considerations. This also includes material innovations such as low-carbon concrete and strategies such as designing for reuse.

One possibility for material choice in PED planning and construction processes is sustainable material sourcing such as timber sourced from sustainably managed, biodiverse plantation forests to avoid the degradation of old growth areas to maximize carbon sequestration. Where useful, fast-growing bio-based materials such as bamboo and hemp can be used as alternatives to timber.

Secondly, PEDs have a direct impact on land use change through constraints on urban growth by making better use of already converted land to prevent urban sprawl and land and forest degradation. How transport and infrastructure are planned directly influences further deterioration of the quality of forest land, especially of old forests. City governments and utilities can develop PED policies and invest directly in protecting and restoring their local forested catchments to improve the delivery of ecosystem services, including improving water quality and seasonal river resilience: lower flood risk downstream; temperature control; improve biological diversity and increase cultural value.

As the focus of this work was to take a closer look at the concept of PB to find out how this concept can help to establish a holistic sustainability evaluation of PEDs, we found that the concept of PB can be used when planning PEDs. When analyzing the key performance indicators of PED concepts (Table 4), it became clear that there are two PBs that are directly related to the indicators used in the PEDs:

In the following, we discuss further how the PED concept relates to PB and which other boundaries might be important when planning PEDs.

The discussion highlights the need for a comprehensive understanding of the different aspects impacting sustainability in terms of PB of PEDs.

The study of the two PED cases in Norway and Switzerland showed that both concepts do not focus on the PB. In the case in Norway, a set of KPIs was developed that mainly tries to minimize impact compared to a “base case”. Then certain measures can be used to offset the impact (e.g., the renewable electricity produced onsite can be used to offset GHG emissions from the grid). This concept is therefore heading for a better than usual approach and not congruent with the PB approach, which is framing precise thresholds for development. In Switzerland, on the other hand, the PED concept of 2000 WS does not try to stay within the PB. On the contrary, a 2000 W power use is allowed for every citizen. Even though this implies a very small footprint, it allows certain PB to reach and crossover.

There are two aspects that need to be integrated: First, starting with PEDs, there should be a focus on a regenerative model for the built environment that allows us to plan the built environment to stay within the PB. Incorporating PB into environmental and sustainability assessments in PED projects is imperative. This requires PB thresholds to be downscaled to a manageable PED scale.

Secondly, the overshoot of several PB indicates that we need to develop strategies to regenerate the Earth system and how we impact it. This will require a fundamental shift in the way we think about our relationship with the planet. We have to re-think what a balanced human–planet relationship might look like and define PB that limit our impact on the earth system.

In conclusion, the concept of PB can help to establish a holistic sustainability evaluation of PEDs as a framework for the transformation of districts. However, it seems a concerted effort is needed to integrate the nine PB into PED sustainability evaluation schemes. The KPIs used in PEDs need to include the PB if we want to use PED developments to stay within the PB.