9.1 Introduction

By this stage of the book, it should be clear that housing is critical for our society for a range of reasons. Housing primarily provides us with a place to shelter from the elements and gives households their own private space, and the provision of adequate housing is a basic human right. The UN states that adequate housing must address security of tenure, availability of services, materials, facilities and infrastructure, affordability, habitability, accessibility, location, and cultural adequacy [1]. Many of these basic housing requirements can be addressed through the provision of sustainable housing, as we have described in earlier chapters. Given the climate emergency and wider social challenges related to housing, we believe that environmental and social sustainability considerations of housing must be included within the basic elements of housing promoted by the UN.

Despite knowing the importance of housing, there are significant environmental, social, and financial issues with the current provision of housing in many jurisdictions [2,3,4,5,6,7,8]. Current housing has a significant negative environmental impact, it is making people sick, and it is increasingly unaffordable to own, rent, and live in [9,10,11,12,13,14,15,16,17,18,19]. Globally, we have an increasing number of examples (see Chaps. 6 and 7) where the type of sustainable housing we are advocating for in this book is already being provided, for both new and existing housing and at different scales and through different approaches. While not all examples are perfect, they demonstrate that we can be doing significantly more right now. There is no need to wait for more technological innovation, for design knowledge, or for evidence of performance to provide sustainable housing; we just need to get on with doing it.

In this final chapter, we revisit the core ideas woven throughout the book. We summarize the current situation and how the current provision of housing will not meet our environmental or societal needs moving forward. Despite the mounting evidence of the benefits of sustainable housing, we still face key challenges that need to be urgently addressed to ensure we can deliver a sustainable housing transition that includes everyone. We discuss the prospects for change and explore where that change needs to occur. We finish the chapter with some concluding reflections.

9.2 Sustainable Housing: Current Context, Future Challenges

Following decades of fragmented or limited action on climate change, we are in the middle of a climate emergency [20, 21]. Already, we are experiencing the impacts of a changing climate on our built environment. For example, there is an increase in the frequency and severity of extreme weather events (e.g., heatwaves) and disasters (e.g., fires, floods), and this is predicted to get worse moving forward [20, 22]. The consensus among climate and environment scientists is that we will need to reduce our global emissions by 80% or more by 2050 to mitigate catastrophic climate change [20, 21]. Our individual and collective response to this climate emergency will shape our short-term future and have impacts for future generations.

However, in relation to environmental sustainability, it is more than just needing to significantly reduce carbon emissions. We have known for more than 50 years that we were not sustainably consuming resources and we have been consuming non-renewable resources at a rate faster than they can be regenerated [23]. Recent data suggests that we are consuming our earth’s resources at the rate of 1.75 planets per year and there is limited evidence that this is changing any time soon [24]. Clearly, we are not living within the means of our one planet and have not taken the significant steps required to address this, despite the plethora of warnings for what is likely to occur should we not heed these warnings and respond to them.

There has been some promising global progress in recent years towards addressing climate change and other environmental and societal challenges. UN Climate Change Conferences of the Parties in 2021 and 2022 moved the global discussion forward with agreements for more stringent and urgent action. However, there are many sustainability advocates who argue these recent agreements do not go far enough given the current climate emergency. The UN’s Sustainable Development Goals are another global initiative and have also helped focus attention on delivering key improvements across their 17 goal areas [25]. However, as researchers and other advocates have argued, incremental policy and practice change is not sufficient for addressing the climate emergency; we need to do much more across a shorter timespan if we are to avoid the most catastrophic of climate change outcomes [3, 26, 27].

The housing sector has a critical role to play in delivering a more sustainable future. Globally, the housing sector contributes around 17% of total greenhouse gas emissions and consumes around 19% of total energy demand [3, 28]. Additionally, the housing sector consumes 30–50% of raw and recycled materials for building new housing and retrofitting existing housing [29]. The impact from materials occurs through the use of materials and the generation of waste during construction, through-life (maintenance), and at end of life. Given that housing is a long-life infrastructure, any transition to a low carbon future must include sustainable housing.

In this book, we define sustainable housing as dwellings with a zero carbon impact that, where possible, contribute to regeneration initiatives that support wider sustainability. Sustainable housing is housing that significantly reduces its life cycle impacts and engages with concepts of the circular economy (e.g., design for disassembly). However, it is more than just physical elements; sustainable housing improves health and well-being, reduces living costs, and connects to other sectors such as transport, food, and energy networks. Sustainable housing draws on a variety of design, material, technology, and construction innovations to build housing that will perform well now and into the future. This is not just performance from a technical perspective, but also in terms of resiliency against a changing climate (e.g., resilient to extreme weather events).

Sustainable housing is about more than just reducing environmental impact. It is about addressing a range of wider social and financial issues across the housing sector in many regions of the world. Housing is imperative to meet our basic human needs [1] and should provide us with safe, secure places to live, and improve social outcomes like health and well-being. Despite this, we continue to see challenges with the provision of adequate housing around the world. For example, more than 1 billion people live in slums or informal settlements, and more than 100 million people are estimated to be without homes entirely [30]. There are also significant housing affordability issues for many who do have access to housing, with the cost of purchasing and renting increasing at a faster rate than incomes in many jurisdictions over recent decades [6]. As a result, housing is precarious for a growing percentage of the population and this is being exacerbated by rising cost of living (e.g., costs for energy).

It is not just the provision of housing that is important. Research demonstrates that good design, quality, and performance can improve a range of outcomes for households including improving their health and well-being, reducing living costs, and adding resale value, in addition to reducing environmental impacts [31,32,33,34,35]. Conversely, poor design, quality, and performance have been found to negatively impact these outcomes [2, 7, 11, 15, 17, 18, 34, 36,37,38,39,40]. When replicated at a larger scale, the benefits go beyond individual dwellings to the wider community. For example, the use of vegetation can help improve thermal performance of a single dwelling, but large-scale urban greening can help reduce air temperatures in heatwaves by 15 °C or more [41,42,43,44]. This not only helps make our climate more comfortable, but it also reduces the need for mechanical heating and cooling and reduces health and mortality outcomes.

While each climate zone has nuances in terms of how to deliver sustainable housing, the evidence from around the world shows there are some broad rules we should all be following [45,46,47]. These relate to new housing, but many are also relevant for existing housing. At the individual dwelling level, this includes (but is not limited to):

  • Optimizing orientation to maximize passive solar performance,

  • Improving thermal performance of the building envelope through improved material use and insulation,

  • Sealing up gaps and cracks,

  • Block out curtains/blinds for windows,

  • Improving window performance through advance glazing solutions,

  • All-electric houses with heat pump technology for heating, cooling, hot water,

  • Energy efficient appliances,

  • Smart homes,

  • Renewable energy technologies (e.g., solar PV and batter storage), and

  • Utilizing nature around the dwelling to help regulate thermal performance.

Despite the benefits of sustainable housing, only a small percentage of the current housing market achieves design, quality, and performance outcomes in line with what is required for a low carbon future [4]. This low uptake points to significant neo-classical market failures. The current housing regime operates on the idea that sustainable housing can be left to the wider consumer market to drive demand and create competition, innovation, and cost efficiency. This idea has been widely criticized and been shown to not deliver the type of outcomes needed at the speed required. However, there is a small section of the market that is using information about dwelling design, quality, and performance to improve decision making, with emerging research suggesting a tangible financial value for more sustainable houses. Energy Performance Certificates used throughout Europe and elsewhere are an example of this information provision, although at this stage, the speed of consumer change does not match what is required to deliver a low carbon future [48].

To address these market failures, governments around the world have typically used minimum design, quality, and performance requirements by way of regulations [49, 50]. These regulations have arguably had significant success in raising the design, quality, and performance of the bottom of the market, but generally fall short of what is required for a low carbon future. According to the IEA, only around 85 countries have mandatory or voluntary building codes with specific energy requirements, highlighting the challenge in introducing these [4]. Other issues are evident such as ensuring regulations are enforced, as well as the implication of minimum standards being good, rather than being the legally mandated bare minimum. However, leading jurisdictions like the EU and California have introduced a range of advanced regulatory requirements in recent years and now require all new housing to be delivered to a performance level near our definition of sustainable housing [51, 52]. In locations where mandatory requirements are not adequate, or where none exist, the use of voluntary standards like Passive House and Living Building Challenge offer a framework to provide significantly higher design, quality, and performance [53, 54]. Unfortunately, there are many in the wider housing industry who push back against the need for improved regulations or changes through planning systems, saying that such changes add red tape and ultimately add costs to consumers. However, as the evidence and case studies presented in this book indicate, we are now able to provide sustainable housing for little, if any, additional costs for consumers.

Another important lever in the provision of sustainable housing is the use of planning systems. Before a dwelling or community is constructed, land use planning has a critical role to play in terms of determining the ease of delivering improved outcomes for sustainable housing [55,56,57]. For example, if vacant housing lots are planned to optimize dwelling performance, it can result in significant improvement to thermal performance and/or reduce the costs for achieving higher standards. Statutory planning can facilitate other elements related to sustainable housing, such as where housing is located, the types of housing in an area, and considerations of general or specific amenities.

There has also been an increasing use of alternative mechanisms to help address wider market failures and drive the provision of sustainable housing. Examples include consumer education about energy and water efficiency, product labelling programmes, rebates, and tax incentives or subsidies for sustainability technologies or building practices.

A number of challenges are prevalent with the provision of standard housing. Once a dwelling is constructed, the performance and environmental impact has been locked in for many decades. This means it is critical that we ensure all new housing meets much higher standards. To do this we need to focus on the design stage, where the old rule of thumb estimates that around 80% of a dwelling’s impacts are locked in during the first 20% of the design process. Failure to ensure new housing performs to a higher standard means that much of housing not yet built will likely need to undergo expensive retrofits. Research from around the world calculates that it could cost approximately £20,000 or more to provide deep retrofit [58, 59].

New housing is almost the easier housing type to address. With new housing, there are less constraints and more opportunities to provide much more significant outcomes when they are designed in from conception. Addressing the existing housing stock is more challenging. An existing dwelling has a range of constraints that may limit what opportunities are possible to improve sustainability outcomes. If we are to achieve a low or zero carbon housing stock by 2050 (at the latest), it will require significant action on existing housing [2, 3, 59].

Another challenge is how to account for housing and household trends. For example, in some jurisdictions, there has been an increase in the floor area of dwellings over time [60]. This increase in floor area has been found to offset increases in energy efficiency requirements and has occurred while the average number of people per dwelling has been decreasing. Additionally, this increase in floor area means we have more stuff in our homes, further creating complexities in how we provide sustainable housing. The way we use our homes is changing, which can impact the performance of a dwelling. For example, during COVID-19, many people were required to work from home (where possible) despite many dwellings not being designed for such a situation [61, 62]. This created challenges for liveability (e.g., shared work/living spaces with no boundaries between areas) and performance (e.g., at home for more hours therefore consuming more energy for work activities as well as things like heating and cooling).

Scale is also important for understanding and providing sustainable housing, particularly the dwelling scale, neighbourhood and city scale, and state, national, and international scale. This is because each scale presents different opportunities to provide sustainable housing, and we need to leverage these different scales to ensure optimal outcomes are delivered. For example:

  • At the dwelling scale, planning to establish lot layouts and the design of the dwelling are important for optimizing dwelling performance. This allows for improved opportunities to reduce material impacts and integrate sustainability technologies for individual dwellings.

  • At the neighbourhood and city scale, it is about identifying how and where to house populations and opportunities to reduce urban climate change, as well as implementing shared infrastructure between or across dwelling borders.

  • At the state, national, and international level, it is about the larger coordination of addressing climate change, addressing wider social challenges (e.g., affordable housing, fuel poverty), and governance. Additionally, ensuring larger scale infrastructure is in place to support the transition to sustainable housing at an individual dwelling or neighbourhood scale. For example, if energy networks are not able to cope with an increase in small scale renewable energy, it will potentially curtail sustainable housing opportunities.

9.3 Prospects for Deep Structural Change

Throughout this book, we have highlighted the significant challenges limiting the scaling up of the provision of sustainable housing around the world. As touched on in Sect. 9.2, there are various factors contributing to this. What the current context and wider evidence suggests is that, in order to provide sustainable housing at the scale required, we need to challenge the current provision of housing and the existing housing regime. In doing so, we can create deep structural change across the housing sector and the entrenched resistant stakeholders. Building upon the work of other sustainability transitions researchers, we argue that there are ten key socio-technical dimensions that must be addressed if we are to achieve a sustainable housing transition [63]. These socio-technical dimensions are:

  1. 1.

    guiding principles,

  2. 2.

    physical attributes,

  3. 3.

    knowledge,

  4. 4.

    geography,

  5. 5.

    industrial structures, and organizations,

  6. 6.

    markets, users, and power,

  7. 7.

    policy, regulations, and governance,

  8. 8.

    everyday life and practices,

  9. 9.

    culture, civil society, and social movements, and

  10. 10.

    ethical aspects.

We have provided numerous case studies in Chaps. 6 and 7 that demonstrate how these socio-technical dimensions are already being addressed in real world, sustainable housing projects. These case studies demonstrate what is possible. While we do not argue that all these case studies are perfect, they do offer significant insights into how we are (and can) already be providing housing that is much more sustainable. The case studies provide us with an opportunity to move the sustainable housing transition from the pre-development phase, through to the take-off phase, ultimately leading to an acceleration phase, and then stabilization of a new sustainable housing regime. These case studies, and our reflection of sustainability transition theory, extend recent research exploring the sustainable housing transition and how to facilitate the scaling up of solutions [27, 31, 50, 63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80].

The reality is that we have no other option than to transition to a sustainable housing future. The question is how can it be achieved, over what time frame, and how do we ensure no household is left behind? The current approach of housing provision will leave sustainable housing in the pre-development phase, to those who can afford to obtain it. Those without the financial resources will be left behind. This will create an even wider divide of housing quality and performance based on a household’s financial position. However, a more coordinated approach could ensure that those who are more vulnerable in our society are also able to engage with sustainable housing and the benefits that such housing provides. It is vulnerable and lower-income households who will benefit most from a sustainable housing transition in terms of the day-to-day impact of improved health and well-being outcomes and reduced living costs.

The case studies in this book offer hope that we can achieve a sustainable housing transition and a template for what we can provide. However, many of these cases have had challenges in getting to where they are now. For example, the Cape Paterson ecovillage in Australia will have taken almost 25 years from initial conception and purchase of the land, navigating the planning approval process, and construction of the site [81]. This is simply too long a time frame if we are to deliver on sustainability goals by 2050. What we need is a coordinated approach across a range of stakeholders.

Policy makers need to implement significantly stronger regulations to lift housing quality and performance. These regulations should be developed with a pathway to delivering sustainable housing by no later than 2030 for all new housing. Policy makers must also ensure that a pathway for retrofitting existing housing is developed, with sufficient support for households and the wider housing construction industry to help facilitate a scaling up retrofits. This should be based on evidence about the existing housing stock’s quality and performance, with the worst quality and performing housing addressed first.Footnote 1 Where evidence is not available, governments should prioritize collecting robust data sets on the condition of existing housing. Retrofit policies should be planned to scale up to ensure that the industry can develop required skills and capacity, and retrofit targets should be based on longer term sustainability goals. As a worst-case scenario, retrofits for all existing housing should be completed by 2050, but we would argue for a more ambitious timeframe of no later than 2040.

Housing construction industry stakeholders have a significant opportunity to drive the sustainable housing transition. Because of their size and reach, key stakeholders such as large-scale housing developers and builders have the opportunity to lead by example and create significant change. Such stakeholders should be able to leverage their existing (or new) supply chains with economies of scale to ensure that any costs for the transition are kept low. There are significant market advantages for early adopters in that they will likely establish themselves as the authorities in the industry. However, this is easier said than done with significant resistance to change being an ongoing challenge. Education and support for housing construction industry stakeholders will be required to help create wider change, but it may not be enough on its own. Innovative financing or other options like fast tracking planning approval processes may also help drive an incentive for stakeholders to go beyond minimum standards.

Housing consumers need to become more educated about the decisions they make with their housing choices. While many people will not have many (or any) choices (e.g., renters in constrained housing markets), there are others who can use their decision making power to help influence the wider housing sector. However, given the complexity of some elements of sustainable housing (e.g., technologies), consumers should not be expected to understand all the details of a house—much like we would not know all the complexities of a TV or car we were purchasing. It is critical that the provision of information about the performance of a dwelling is clear, robust, and verifiable. There are examples already available that demonstrate this, such as the Energy Performance Certificates across Europe which are providing consumers with better information. However, these certificates will need to evolve to align with developments in the sustainable housing space (e.g., how to deal with two-way batteries in an electric vehicle). Perhaps the most important thing for consumers is to demand to be placed at the centre of housing decisions. It is these consumers who will live in the dwelling and feel the impacts of poor quality and performance. They should not be an afterthought.

Researchers also have a critical role moving forward. Robust evidence will be required to inform the sustainable housing transition and help guide policy making and industry changes. This needs to include both the successes and failures of sustainable housing. Research is required to drive innovation of design, materials, and technologies, but also to better understand how sustainable housing performs in the real world. There needs to be improved connection between technical and social research as there is limited benefit from scaling up technology if it is not being used appropriately by households. Social research can also provide necessary information about changing demographics and cultural practices, as well as support stronger equity considerations in housing provision and outcomes. While there is a significant amount of evidence already available, researchers need to be better at translating this evidence for policy makers, the housing sector, and consumers. We also encourage researchers to be more ambitious with their research, especially in discussing the implications of their research. As a research community, we must look beyond short-term research and at longer time horizons. Let us challenge the research community to be a key driver of sustainable housing (and wider sustainability). To do this, we need to move beyond the conservative nature of our research and challenge policy makers and the housing construction industry to do more.

In Chap. 8, we provided some thoughts on what an ambitious but realistic pathway would look like. In summary, we suggest all jurisdictions:

  • Introduce a policy pathway that sets out short to medium term policy goals to deliver new sustainable housing by no later than 2030. This will provide all stakeholders confidence on the future direction of housing quality and performance.

  • Introduce a requirement for mandatory disclosure of a dwelling’s quality and performance to be used at point of sale or lease for existing housing by 2025. This information must be robust, reliable, and transparent to ensure confidence.

  • Set a lifting of minimum performance requirements that are triggered when a dwelling is sold or rented. These requirements should increase over a clear period of time. Drawing upon the European Energy Performance Certificate rating scale, it would not be unreasonable to expect that minimum performance requirements could be improved from an E in 2025 to D in 2028, C in 2031, and B in 2034 (allowing for three years between minimum performance changes). From 2035 onwards, requirements for existing housing at point of sale or lease could be aligned with new housing requirements.

While this book has largely been focussed on developed countries, a global sustainable housing transition must include developing countries. The housing challenges in developing countries are often different from those in developed countries, and we must ensure that the sustainable housing transition in those locations can help address some of these different challenges. Much like with the global climate change approach, we will need developed countries to help support developing countries with the sustainable housing transition. This can be through sharing of knowledge, skills, materials, technologies, and research, but also likely through financial support to help such countries transform their housing industries.

9.4 A Final Reflection

While it may seem like a monumental task to provide the types of housing we talk about in this book, the evidence and case studies throughout the book offer us hope and guidance. There are policy makers, housing construction industry stakeholders, and housing consumers who have worked within their systems to drive change, as well as those who have pushed to create new ways of doing things. There are jurisdictions around the world banning the use of fossil fuels and incentivizing the electrification of dwellings. There are developers and architects straying from the path and delivering radically different and more sustainable housing options. There are consumers advocating for change and demonstrating alternative ways to live. But we only have a short window of time (perhaps no more than 15 years) to ensure that we change the way we provide housing. It is imperative that we scale up, embed, and mainstream these changes and alternatives, and leverage this progress to facilitate a global transition to sustainable housing. We also need policy makers, housing construction industry stakeholders, and housing consumers to collaborate to ensure the sustainable housing transition is undertaken in the most efficient and effective way. This might seem like a challenge, but as the evidence and case studies demonstrate, this type of housing future is possible.