Energy sufficiency in buildings and cities: current research, future directions

1.1 Defining (energy) sufficiency

A starting point can be Princen’s (2005: vii) seminal work on the logic of sufficiency, stemming from his observations that there is widespread acknowledgement that the environmental crisis is ‘a human problem’. Societies lack ‘principles of social organisation consistent with long-term, sustainable resource use’ (viii); and that humans have a long history of living within ecological constraints. He saw sufficiency as an organising principle for sustainable living and offered an initial definition of this principle as ‘a sense of “enoughness” and “too muchness”’. Princen makes a striking move away from positivist worldviews, writing of effective (sufficiency-oriented) decision-makers as people who see the world as one where:

Princen offers examples of how sufficiency can be practiced and achieved, even in a region (North America) where a sense of boundless opportunity and resources often combines with a narrowly science-based approach to enquiry and development.

The principle of sufficiency challenges some deeply entrenched modes of understanding human activity, notably neoclassical economics. Sufficiency as an organising principle takes one beyond efficiency (e.g. Wilhite & Norgaard 2003; Princen 2005; Darby 2007), questioning the nature of demand rather than seeking to meet any form of demand at minimum cost. The qualitative issue of wellbeing as an element of sufficiency is also important. Jackson (2016: 22) offers a guide by describing prosperity as going:

The ‘doughnut economics’ model of a ‘safe and just space for humanity’ (Raworth 2017) moves the discussion into a realm of post-growth economies that would prioritise human wellbeing in both qualitative and quantitative terms, within ecological limits. This raises many debatable issues, some of which are addressed in this issue, but opens possibilities for action and experiment at a time when they are urgently needed.

The concept paper on energy sufficiency commissioned by the European Council for an Energy-Efficient Economy (ECEEE) also focussed on meeting basic needs within limits. It defined energy sufficiency as:

This involves not only going beyond efficiency as an organising principle but also differentiating energy services or ‘satisfiers’ from needs (Max-Neef 1991; Gough 2017). It also means unpacking the many ways in which energy services and usage are understood, and moving beyond the remit of ‘behaviour change’ to reduce energy demand (usually at the individual level) to grapple with more complex understandings of access to decent living conditions, equity, power and social change dynamics. As examples, recent studies have developed frameworks such as consumption corridors (Fuchs et al. 2021; Büchs et al. 2023) and related the notion of decent living standards to energy needs (Rao et al. 2019; Millward-Hopkins et al. 2020).

1.2 Energy sufficiency and policy for buildings and cities

While energy and climate policies have tended to focus on the promotion of energy efficiency and renewable energies, there is no evidence that these measures alone will suffice to meet climate and sustainable development goals, with the latter being taken as the ‘global floor’ of decent living standards. Lage et al. (2023) demonstrate how citizens’ assemblies in 10 European countries are recognising the importance of sufficiency policies; in this, they tend to be ahead of their governments. Scholars and policymakers who are sceptical of technological ‘silver bullet’ solutions are attending more to the need to reduce overall energy demand and improve energy security. For example, Barrett et al. (2022) offer a framework for estimating the potential for energy demand reduction at the national level and apply it to the UK, where they estimate that reductions of 52% between 2020 and 2050 are possible without compromising quality of life. The European Union aimed for a 15% reduction in gas usage following the invasion of Ukraine by Russia (and achieved an 18% reduction¹); research from India also highlights the significance of demand for security (Narula et al. 2017).

The concept of sufficiency is now making its way into policy. A notable example is the 6th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), where a much-cited footnote defines sufficiency policies as:

In relation to cities, the latest IPCC (2023) Climate Change 2023. Synthesis Report. Summary for Policymakers underlines the importance of urban systems for ‘achieving deep emissions reductions and advancing climate resilient development […]’ (29, section C.3.4); the need to link energy sufficiency to buildings and cities is the impetus behind this special issue.

Before this special issue, a small body of literature had focused on applying sufficiency ideas to buildings and cities (Jungell-Michelsson & Heikkurinen 2022). This includes Bierwirth & Thomas’s (2019) concept paper, which focused on four characteristics of buildings—space, design and construction, equipment, and use—and explored how energy sufficiency actions, potentials and policies relate to these. Cohen (2020) investigated the idea of ‘sufficient home size’ and presented five cases demonstrating more ‘environmentally tenable and globally equitable’ forms of housing in high-income countries; Lorek & Spangenberg (2019) presented examples of housing projects guided by sufficiency criteria, and outlined the potential roles of different actors. The purpose of this special issue is to explore these ideas further, especially to explore how pathways towards energy sufficiency can be developed and consolidated for cities, buildings and infrastructures.

2.1 Towards shared understandings of sufficiency

First, papers that focus on how different actors might come together to understand, discuss or accept sufficiency measures can be divided by type of actor: working either directly with citizens or with practitioners, policymakers and other actors. For work with citizens, many of the papers focus on the challenge of sufficiency with regards to living spaces, against the backdrop of an ageing population in Europe and the need to adapt housing size over the life course. The home is more than space, however, and the challenge of achieving this shift to smaller, more sustainable housing, while maintaining social attachments to place, is underscored by all the contributions. All authors recognise the complexity of achieving a shift towards smaller, sustainable housing. As Lehner et al. note, ‘downsizing of living space is not a politically recognized solution in the EU’ (216).

2.2 Estimating the potential of sufficiency measures

Another set of papers moves beyond discussing and debating the potential of sufficiency to proposing tools for estimating its potential. Two are focused on providing new models that integrate sufficiency considerations, with an emphasis on housing density; the third considers how energy sufficiency might be integrated into existing building audits that seek to assess energy efficiency. These studies all point to the need to develop tools that can be useful toward quantifying sufficiency and furthering its applicability.

Subin et al. focus on the potential for land-use reforms in the US, and how sufficiency could be made more relevant to policymakers in relation to land-use planning, in light of housing shortage and affordability issues. Car-oriented planning is a focal point for this study, which provides a quantitative scenario to study the potential impact of placing new housing growth in relatively low vehicle-miles-travelled areas. In studying each US state plus the District of Columbia (DC), with the exception of Alaska, the results underscore the importance of infrastructural conditions for sufficiency, which are difficult to meet in a strongly car-dependent society. The results of their study demonstrate that Texas, California and Florida have the largest absolute emissions reduction opportunity, and that building neighbourhoods where people can drive less is comparable with the uptake of electric vehicles in terms of carbon savings.

Another contribution on modelling focuses on India in a context of rapid urbanisation. Lall & Sethi provide a conceptual framework for sufficiency in residential buildings that accounts for building features such as height and floor area ratio, while also considering the importance of passive cooling design strategies, adaptive thermal comfort and rooftop solar photovoltaic (PV) integration. While high-density urban development is often studied, the authors address a blind spot regarding the vertical dimension of urban growth. Models were then built to explore optimal forms and densities for low- to middle-class housing in Indian cities. The results demonstrate that at the urban scale, a scenario that promotes low-rise (four storeys) and high-density built environments is most desirable, as it balances land utilisation for compactness with low embodied and operational energy intensity and allows for optimal PV installations. Energy sufficiency in building is thus conceptualised as a relative and dynamic measure amidst economic disparities in the developing world, and it is illustrated that it can be operationalised through urban planning regulations.

Turning now to Europe, Fouiteh et al. consider how energy sufficiency measures could be integrated into building energy audits for small and medium-sized enterprises (SMEs) in Geneva, Switzerland, as a way to accelerate change. Semi-structured interviews with experts (researchers, policymakers, organisations and energy advisors) were conducted to further understanding of how sufficiency could be integrated in building audits, and close to 300 sufficiency measures were analysed. A questionnaire was developed for SMEs in Geneva to enquire how they might accept sufficiency measures. Results demonstrate that most energy sufficiency measures are cost-effective and that certain measures can lead to substantial savings. For this to be achieved, auditors need to be trained on what sufficiency is, and how such measures can be integrated into best practices. However, recognising the financial benefits of energy efficiency measures needs to be balanced with fostering a genuine commitment to the concept of sufficiency.

2.3 Learning from sufficiency measures and experimenting with sufficiency

A series of papers examines sufficiency measures that exist, particularly in relation to the building sector, but also in relation to sharing. One paper also explores an experiment to reduce indoor space heating as a way to engage people in experiencing sufficiency.

Bagheri et al. begin by addressing the double challenge faced by the German building sector to meet emission targets and provide affordable housing in rapidly growing cities. Optimising the allocation of living space becomes an appealing idea, and could potentially be supported by sufficiency policies such as flat exchanges, a financial bonus for moving or the provision of moving advice. Based on qualitative interviews with German housing companies, the study finds that flat swapping has limited success due to high financial and social transition costs, limited matching offers and emotional attachment. Additionally, the location and size of available flats play a key role in the decision to move. Financial bonuses would need to complement these measures, and further research is necessary to identify additional constraints hindering success and to work towards increasing the effectiveness of these measures.

Huber et al. conducted neighbourhood-level case studies in France and Germany to distinguish different families of sharing practices and suggest infrastructural measures to support their normalisation. Based on resident diaries and interviews, popular sharing practices are identified, ranging from the sharing of goods, spaces and food to mobility carriers. Informed by social practice theory, the authors then explore meaning elements that are frequently involved in these popular practices and cluster them into four groups. Building on these meaning clusters, two main types of sharing practices are identified: convenience- and community-oriented. To support the establishment of these two ‘families of sharing’, several infrastructural measures are proposed. Thus, convenience-oriented sharing practices may be promoted by infrastructures and associated services that optimise the availability of sharing facilities and minimise temporal stretches and the consumption work involved in practice performances. Community-oriented sharing practices may benefit from infrastructural arrangements that enable chance encounters, privilege community spaces over private areas and create welcoming spatial atmospheres.

Expanding on the concept of ‘heating the body, not the building’, van Moeseke et al. investigate the development of a sufficient heating practice, its potential impact on energy consumption, and the barriers and opportunities for its implementation. Supported by the availability of a range of personal comfort systems (e.g. heated blankets, electric heaters), 23 households in Brussels, Belgium, experimented over three years with reducing indoor temperatures while remaining comfortable. Heating energy savings of 50% were achieved, with co-creation and mutual support being important in enabling the establishment and maintenance of the new practices. This example demonstrates the potential of experiments, where people are willing to challenge indoor comfort norms and expectations.

2.4 Conceptual developments: justice, elites and reprogramming

Several papers propose conceptual developments in sufficiency studies that help to chart future directions for research and action by relating to theories of justice, focusing on elite consumption, or considering ways to engage in sufficiency with existing material and institutional arrangements.

Guilbert focuses on the ‘energy crisis’ in winter 2022/23, at a time when the Swiss government was bracing its population for blackouts or possible energy cuts. Based on a survey and in-depth interviews in Geneva with household members, and interviews with building managers, Guilbert found that different measures and recommendations did lead to efforts to reduce energy usage in buildings, but that flaws were also revealed through applying an energy justice framework. Notably, there were important discrepancies between low- and high-income tenants, and between tenants and owners, among others. Guilbert argues that it is necessary to recognise residents’ vulnerabilities, unequal housing conditions, the limited agency of certain groups and thus the need for differentiated responsibilities when it comes to acting on change.

Related to questions of justice, Koch et al. critically review the sufficiency debate and state of research on elites, arguing that research on sufficiency and elite consumption may interact to be mutually beneficial, and for a greater focus on elites by sufficiency researchers. The assumption put forward is that much research has been focused on how to ensure adequate ‘social floors’ when it comes to sufficiency measures. Yet there are structural barriers to achieving sufficiency through the implementation of ‘ecological ceilings’ for production and consumption, referencing Gough (2020). The argument is illustrated with examples from urban spaces that are increasingly structured to accommodate the preferences of economic elites. For the authors, these structural barriers to sufficiency would be facilitated by a systematic account of extreme wealth and:

Christensen et al. propose the concept of ‘reprogramming’, which involves modifying or adjusting existing material arrangements and institutions in ways that promote general shifts to resource-light practices. The main assumption is that the adoption of less resource-intensive everyday practices will need to take place within existing material arrangements and institutional settings, which were created in times of fossil fuel abundance. Two rounds of in-depth interviews were conducted with 31 young Danish adults in city apartments, all of whom moved to another home during the interview rounds. The concept of reprogramming is exemplified through empirical findings, particularly focusing on mobility practices among young adults. The paper reminds readers that sufficiency can be about reorienting what already exists, thus reducing the need for materials as well as lessening energy flows; it also brings together concepts from social ecology with those of social practice theory.

2.5 Methods

To conclude, a word on methods: a range of methods has been used to explore sufficiency, with interviews, focus groups, surveys and modelling, and combinations of these, seen in many papers. Other methods include citizen and stakeholder ‘thinking labs’ (Lehner et al.), imagining futures (Moynat & Sahakian) or backcasting with focus groups (Aagaard & Christensen), combining a real-world laboratory and a co-creation approach including the authors, who were also subjects of the research (van Moeseke et al.), and creating a design game for use with housing professionals (Graham et al.). Some authors reused existing datasets to unearth insights relevant to sufficiency, whereas others gathered new empirical data or undertook modelling specifically to answer sufficiency-related questions. The combination of established and more exploratory or playful methods, and different types of data, suggests a vibrant and growing research community.