Furman, S., Martínez, A., & Martín  , X. (2024). Social housing retrofit: Case studies in resident engagement. In: Madrazo, L. (Ed.). Proceedings of the RE-DWELL Conference 2024 - Sustainable Living, Affordable Homes: Meeting the Challenge Together (pp. 99-102). Ramon Llull University, Barcelona, Spain.

Buildings are responsible for approximately 40% of energy consumption and 36% of greenhouse gas emissions in the EU (European Commission, 2021). Energy retrofit is also referred to as building energy retrofit, low carbon retrofit, energy efficiency retrofit and energy renovation; all terms related to the upgrading of existing buildings energy performance to achieve high levels of energy efficiency. Energy retrofit significantly reduces energy use and energy demand (Femenías et al., 2018; Outcault et al., 2022), tackles fuel (energy) poverty, and lowers carbon emissions (Karvonen, 2013). It is widely acknowledged that building energy retrofit should result in a reduction of carbon emissions by at least 60% compared with pre-retrofit emissions, in order to stabilise atmospheric carbon concentration and mitigate climate change (Fawcett, 2014; Outcault et al., 2022). Energy retrofit can also improve comfort, convenience, and aesthetics (Karvonen, 2013). There are two main approaches to deep energy retrofit, fabric-first and whole-house systems. The fabric-first approach prioritises upgrades to the building envelope through four main technical improvements: increased airtightness; increased thermal insulation; improving the efficiency of systems such as heating, lighting, and electrical appliances; and installation of renewables such as photovoltaics (Institute for Sustainability & UCL Energy Institute, 2012). The whole-house systems approach to retrofit further considers the interaction between the climate, building site, occupant, and other components of a building (Institute for Sustainability & UCL Energy Institute, 2012). In this way, the building becomes an energy system with interdependent parts that strongly affect one another, and energy performance is considered a result of the whole system activity. Energy retrofit can be deep, over-time, or partial (Femenías et al., 2018). Deep energy retrofit is considered a onetime event that utilises all available energy saving technologies at that time to reduce energy consumption by 60% - 90% (Fawcett, 2014; Femenías et al., 2018). Over-time retrofit spreads the deep retrofit process out over a strategic period of time, allowing for the integration of future technologies (Femenías et al., 2018). Partial retrofit can also involve several interventions over time but is particularly appropriate to protect architectural works with a high cultural value, retrofitting with the least-invasive energy efficiency measures (Femenías et al., 2018). Energy retrofit of existing social housing tends to be driven by cost, use of eco-friendly products, and energy savings (Sojkova et al., 2019). Energy savings are particularly important in colder climates where households require greater energy loads for space heating and thermal comfort and are therefore at risk of fuel poverty (Sojkova et al., 2019; Zahiri & Elsharkawy, 2018). Similarly, extremely warm climates requiring high energy loads for air conditioning in the summer can contribute to fuel poverty and will benefit from energy retrofit (Tabata & Tsai, 2020). Femenías et al’s (2018) extensive literature review on property owners’ attitudes to energy efficiency argues that retrofit is typically motivated by other needs, referred to by Outcault et al (2022) as ‘non-energy impacts’ (NEIs). While lists of NEIs are inconsistent in the literature, categories related to “weatherization retrofit” refer to comfort, health, safety, and indoor air quality (Outcault et al., 2022). Worldwide retrofit schemes such as RetrofitWorks and EnerPHit use varying metrics to define low carbon retrofit, but their universally adopted focus has been on end-point performance targets, which do not include changes to energy using behaviour and practice (Fawcett, 2014). An example of an end-point performance target is Passivhaus’ refurbishment standard (EnerPHit), which requires a heating demand below 25 kWh/(m²a) in cool-temperate climate zones; zones are categorised according to the Passive House Planning Package (PHPP) (Passive House Institute, 2016).  

Environmental Retrofit Buildings are responsible for approximately 40% of energy consumption and 36% of carbon emissions in the EU (European Commission, 2021). Environmental retrofit, green retrofit or low carbon retrofits of existing homes ais to upgrade housing infrastructure, increase energy efficiency, reduce carbon emissions, tackle fuel poverty, and improve comfort, convenience and aesthetics (Karvonen, 2013). It is widely acknowledged that environmental retrofit should result in a reduction of carbon emissions by at least 60% in order to stabilise atmospheric carbon concentration and mitigate climate change (Fawcett, 2014; Johnston et al., 2005). Worldwide retrofit schemes such as RetrofitWorks, EnerPHit and the EU’s Renovation Wave, use varying metrics to define low carbon retrofit, but their universally adopted focus has been on end-point performance targets (Fawcett, 2014). This fabric-first approach to retrofit prioritises improvements to the building fabric through: increased thermal insulation and airtightness; improving the efficiency of systems such as heating, lighting and electrical appliances; and the installation of renewables such as photovoltaics (Institute for Sustainability & UCL Energy Institute, 2012). The whole-house systems approach to retrofit further considers the interaction between the occupant, the building site, climate, and other elements or components of a building (Institute for Sustainability & UCL Energy Institute, 2012). In this way, the building becomes an energy system with interdependent parts that strongly affect one another, and energy performance is considered a result of the whole system activity. Economic Retrofit From an economic perspective, retrofit costs are one-off expenses that negatively impact homeowners and landlords, but reduce energy costs for occupants over the long run. Investment in housing retrofit, ultimately a form of asset enhancing, produces an energy premium attached to the property. In the case of the rental market, retrofit expenses create a split incentive whereby the landlord incurs the costs but the energy savings are enjoyed by the tenant (Fuerst et al., 2020). The existence of energy premiums has been widely researched across various housing markets following Rosen’s hedonic pricing model. In the UK, the findings of Fuerst et al. (2015) showed the positive effect of energy efficiency over price among home-buyers, with a price increase of about 5% for dwellings rated A/B compared to those rated D. Cerin et al. (2014) offered similar results for Sweden. In the Netherlands, Brounen and Kok (2011), also identified a 3.7% premium for dwellings with A, B or C ratings using a similar technique. Property premiums offer landlords and owners the possibility to capitalise on their  retrofit investment through rent increases or the sale of the property. While property premiums are a way to reconcile          split incentives between landlord and renter, value increases pose questions about long-term affordability of retrofitted units, particularly, as real an expected energy savings post-retrofit have been challenging to reconcile (van den Brom et al., 2019). Social Retrofit A socio-technical approach to retrofit elaborates on the importance of the occupant. To meet the current needs of inhabitants, retrofit must be socially contextualized and comprehended as a result of cultural practices, collective evolution of know-how, regulations, institutionalized procedures, social norms, technologies and products (Bartiaux et al., 2014). This perspective argues that housing is not a technical construction that can be improved in an economically profitable manner without acknowledging that it’s an entity intertwined in people’s lives, in which social and personal meaning are embedded. Consequently, energy efficiency and carbon reduction cannot be seen as a merely technical issue. We should understand and consider the relationship that people have developed in their dwellings, through their everyday routines and habits and their long-term domestic activities (Tjørring & Gausset, 2018). Retrofit strategies and initiatives tend to adhere to a ‘rational choice’ consultation model that encourages individuals to reduce their energy consumption by focusing on the economic savings and environmental benefits through incentive programs, voluntary action and market mechanisms (Karvonen, 2013). This is often criticized as an insufficient and individualist approach, which fails to achieve more widespread systemic changes needed to address the environmental and social challenges of our times (Maller et al., 2012). However, it is important to acknowledge the housing stock as a cultural asset that is embedded in the fabric of everyday lifestyles, communities, and livelihoods (Ravetz, 2008). The rational choice perspective does not consider the different ways that occupants inhabit their homes, how they perceive their consumption, in what ways they interact with the built environment, for what reasons they want to retrofit their houses and which ways make more sense for them, concerning the local context. A community-based approach to domestic retrofit emphasizes the importance of a recursive learning process among experts and occupants to facilitate the co-evolution of the built environment and the communities (Karvonen, 2013). Involving the occupants in the retrofit process and understanding them as “carriers” of social norms, of established routines and know-how, new forms of intervention  can emerge that are experimental, flexible and customized to particular locales (Bartiaux et al., 2014). There is an understanding that reconfiguring socio-technical systems on a broad scale will require the participation of occupants to foment empowerment, ownership, and the collective control of the domestic retrofit (Moloney et al., 2010).

Improving indoor thermal comfort is a widely agreed motivate for housing retrofit (Femenías et al., 2018; Outcault et al., 2022; Sojkova et al., 2019; Zahiri & Elsharkawy, 2018). Low carbon retrofit of existing social housing tends to be driven by cost, the use of eco-friendly products, and energy savings (Sojkova et al., 2019). Energy savings are particularly important in colder climates where households require larger energy loads for space heating and thermal comfort and are therefore at greater risk of fuel (energy) poverty (Sojkova et al., 2019; Zahiri & Elsharkawy, 2018). Femenías et al.’s (2018) extensive literature review on property owners’ attitudes to energy efficiency argues that renovations are typically motivated by other needs, referred to by Outcault et al (2022) as ‘non-energy impacts’ (NEIs). While lists of NEIs are inconsistent in the literature, categories related to “weatherization retrofit” (Outcault et al., 2022, p.3) refer to comfort, modernity, health, safety, education, and better indoor air quality (Amann, 2006; Bergman & Foxon, 2020; Broers et al., 2022; Outcault et al., 2022). In poorly maintained social housing, however, the desire to improve indoor air quality and thermal comfort will have an impact on energy consumption. Occupants will, for example, use extra heating to feel comfortable in a damp, mouldy, or cold home. (Zahiri & Elsharkawy, 2018).   There are three main technical improvements to low carbon retrofit: (1) enhancing the building fabrics thermal properties; (2) improving systems efficiency; and (3) renewable energy integration (Institute for Sustainability & UCL Energy Institute, 2012). In order for the Passivehaus Institut’s EnerPHit Retrofit Plan to meet Passivhaus standards for indoor air quality, homes must achieve high levels of air tightness complemented by a mechanical ventilation system including heat recovery (MVHR). Specifically, “airtightness of a building must achieve an air change per hour rate of less than 0.6 at 50 Pa of pressure (n50), and have ventilation provided by either a balanced mechanical heat recovery ventilation or demand-controlled ventilation systems” (McCarron et al., 2019, p.297). This airtightness concept is revered for saving energy, avoiding structural damage, and contributing to thermal comfort (Bastian et al., 2022) while requiring no natural ventilation such as open windows. Mechanical HVAC units alter indoor air temperature, air movement, ventilation, noise levels, and humidity (Outcault et al., 2022). But despite known benefits to physical health and clean air, this may not lead to optimum user-comfort. This is because social housing residents have unique housing needs that differ from homeowners (Sunikka-Blank et al., 2018) and cannot be predicted without resident engagement, as residents are experts in the way they live and use their homes (Boess, 2022; Gianfrate et al., 2017; Walker et al., 2014).   Post Occupancy Evaluation after retrofit has found that social housing residents are often unfamiliar with mechanical systems and their sustainable benefits, especially when retrofit occurs without resident input (Garnier et al., 2020). This can lead to misuse, overheating, the prebound effect, and the rebound effect where affordable energy bills lead to excessive heating—at times 25-26°C (Zoonnekindt, 2019)—contributing to performance gaps as high as five times the predicted energy consumption (Traynor, 2019). Other households considered mechanical systems to be bulky, ugly, and noisy, prompting removal, lack of use, and at times emotional distress (Lowe et al., 2018). DREEAM’s Berlin pilot site found one household blocking mechanical ventilation with tissue paper because they considered the air too cold and residents “haven’t been informed about the positive impact of a well working ventilation on their health and on the energy efficiency of the heating in their apartment” (Zoonnekindt, 2019). DREEAM continued the project with Green Neighbours (Zoonnekindt, 2019), an innovative engagement program co-designed with and for residents to better inform mechanical systems usage. However, literature shows (Boess, 2022; Gianfrate et al., 2017; Walker et al., 2014) that informing residents on how to use mechanical systems is unlikely to change use-habits or adequately combat performance gaps. In order to change residents’ energy behaviours, resident stakeholders should be integrated in retrofit decision-making.

The performance gap in retrofit refers to the disparity between the predicted and actual energy consumption after a retrofit project, measured in kWh/m2/year. This discrepancy can be substantial, occasionally reaching up to five times the projected energy usage (Traynor, 2019). Sunikka-Blank & Galvin (2012) identify four key factors as contributing to the performance gap: (1) the rebound effect, (2) the prebound effect, (3) interactions of occupants with building components, and (4) the uncertainty of building performance simulation outcomes. Gupta & Gregg (2015) additionally identify elevated building air-permeability rates as a factor leading to imbalanced and insufficient extract flowrates, exacerbating the performance gap. While post occupancy evaluation of EnerPhit—the Passivhaus Institut certification for retrofit—has shown far better building performance in line with predictions, the human impact of building users operating the building inefficiently will always lead to some sort of performance gap (Traynor, 2019, p. 34). Deeper understanding of the prebound effect and the rebound effect can improve energy predictions and aid in policy-making (Galvin & Sunikka-Blank, 2016). Therefore, the ‘prebound effect’ and the ‘rebound effect’, outlined below, are the most widely researched contributors to the energy performance gaps in deep energy retrofit.   Prebound Effect The prebound effect manifests when the actual energy consumption of a dwelling falls below the levels predicted from energy rating certifications such as energy performance certificates (EPC) or energy performance ratings (EPR). According to Beagon et al. (2018, p.244), the prebound effect typically stems from “occupant self-rationing of energy and increases in homes of inferior energy ratings—the type of homes more likely to be rented.” Studies show that the prebound effect can result in significantly lower energy savings post-retrofit than predicted and designed to achieve (Beagon et al., 2018; Gupta & Gregg, 2015; Sunikka-Blank & Galvin, 2012). Sunikka-Blank & Galvin’s (2012) study compared the calculated space and water heating energy consumption (EPR) with the actual measured consumption of 3,400 German dwellings and corroborated similar findings of the prebound effect in the Netherlands, Belgium, France, and the UK. Noteworthy observations from this research include: (1) substantial variation in space heating energy consumption among dwellings with identical EPR values; (2) measured consumption averaging around 30% lower than EPR predictions; (3) a growing disparity between actual and predicted performance as EPR values rise, reaching approximately 17% for dwellings with an EPR of 150 kWh/m²a to about 60% for those with an EPR of 500 kWh/m²a (Sunikka-Blank & Galvin, 2012); and (4) a reverse trend occurring for dwellings with an EPR below 100 kWh/m²a, where occupants consume more energy than initially calculated in the EPR, referred to as the rebound effect. Galvin & Sunikka-Blank (2016) identify that a combination of high prebound effect and low income is a clear indicator of fuel poverty, and suggest this metric be utilised to target retrofit policy initiatives.   Rebound Effect The rebound effect materializes when energy-efficient buildings consume more energy than predicted. Occupants perceive less guilt associated with their energy consumption and use electrical equipment and heating systems more liberally post-retrofit, thereby diminishing the anticipated energy savings (Zoonnekindt, 2019). Santangelo & Tondelli (2017) affirm that the rebound effect arises from occupants’ reduced vigilance towards energy-related behaviours, under the presumption that enhanced energy efficiency in buildings automatically decreases consumption, regardless of usage levels and individual behaviours. Galvin (2014) further speculates several factors contributing to the rebound effect, including post-retrofit shifts in user behaviour, difficulties in operating heating controls, inadequacies in retrofit technology, or flawed mathematical models for estimating pre- and post-retrofit theoretical consumption demand. The DREEAM project, funded by the European Union, discovered instances of electrical system misuse in retrofitted homes upon evaluation (Zoonnekindt, 2019). A comprehensive comprehension of the underlying causes of the rebound effect is imperative for effective communication with all retrofit stakeholders and for addressing these issues during the early design stages.   Engaging residents in the retrofit process from the outset can serve as a powerful strategy to mitigate performance gaps. Design-thinking (Boess, 2022), design-driven approaches (Lucchi & Delera, 2020), and user-centred design (Awwal et al., 2022; van Hoof & Boerenfijn, 2018) foster socially inclusive retrofit that considers Equality, Diversity, and Inclusion (EDI). These inclusive approaches can increase usability of technical systems, empower residents to engage with retrofit and interact with energy-saving technology, and enhance residents’ energy use, cultivating sustainable energy practices as habitual behaviours. Consequently, this concerted effort not only narrows the performance gap but simultaneously enhances overall wellbeing and fortifies social sustainability within forging communities.

As the name suggests, Post-Occupancy Evaluation (POE) is the process of assessing the performance of a building once it has been occupied. It is often conflated and falls under the umbrella of Building Performance Evaluation (BPE) (Boissonneault & Peters, 2023; Preiser, 2005; Stevenson, 2018). Other definitions refer to POE as any activity intended to assess how buildings perform and the level of satisfaction of their users, ranging from simple survey questionnaires to indoor environmental quality (IEQ) measurements, which makes its scope very broad (Li et al., 2018). Nevertheless, in the case of POE, the focus should be on the occupants’ experience of the building and the impact of spaces on their behaviour and well-being (Watson, 2003 in Sanni-Anibire et al., 2016). It is commonly suggested that POE should be conducted at least a year after the handover and occupation of the building so that users can experience and test it under different weather conditions (RIBA et al., 2016). In the context of housing, housing providers, developers and architecture practices can benefit from enquiring what makes a good design from the occupants’ point of view. A systematic and rigorous POE combined with periodic user experience surveys can be very beneficial as it helps to improve relationships with tenants and provide a better picture of the quality of the housing stock. Thus, POEs do not only help to balance the scale between the social, economic and environmental aspects of buildings but also revitalise the role of research in the whole life cycle of projects. Despite its potential benefits for the various stakeholders engaged in the production of the built environment, POE is not a widespread practice in the sector. There is a notable absence of literature and research on the subject (Durosaiye et al., 2019; Hadjri & Crozier, 2009). However, since the 2010s, there has been a growing academic interest in POE, as evidenced by the increasing number of scientific publications, including studies related to post-occupancy evaluation (Li et al., 2018). There is a consensus in literature that learning from experience, whether from unintended consequences of ill-considered design or from successful projects, through the active involvement of occupants and users of buildings is a pathway for innovation. POE is commonly considered as an activity that requires long-term commitment and can be time and resource-consuming. This is a limitation that can be explained by the short-term logic of the construction sector and the fleeting commitment of developers, especially private and profit-driven, to the communities and clients they work with. In the same vein, the question of who is responsible for commissioning and conducting a POE represents the biggest barrier to its widespread implementation in the sector (Cooper, 2001). Concerns are inextricably linked to the cost and scope of the assessment, the equipment and professionals involved, and the possibility of being held accountable for flaws that might be exposed by the activity. Discussions around the importance of inspecting buildings after completion to assess their environmental performance have gained momentum in recent decades as a consequence of the evidenced climate crisis and the significant share of carbon emissions attributable to activities related to the built environment (according to UNEP (2022), 37 per cent of CO2 emissions in 2021). Nonetheless, the emergence of POE as a concept for the built environment dates back to the 1960s in the USA, where it was originally used to assess institutional facilities and fell mainly within the remit of facility managers (Preiser, 1995). Later, the PROBE (Post Occupancy Review of Building Engineering) research conducted between 1995 to 2002 on 23 non-residential case studies in the UK helped spread the concept among the whole gamut of professionals involved in the design and construction of buildings (Bordass et al., 2001; Cohen et al., 2001). With respect to design and housing, the work of Marcus and Sarkissian (1986) in Housing as if People Mattered is worth mentioning. In this book, the authors have outlined a set of design guidelines derived from evidence gathered through POEs. Their research was conducted with the aim of comprehending people's preferences and dislikes about their neighbourhoods and homes, utilizing a people-centred perspective that delves into " the quality of housing environments from a social standpoint, as defined by residents" (p.5). Their approach to POE is grounded in viewing housing as a process rather than a mere product. They propose rethinking the relationship between the designer and inhabitant, extending beyond the completion of buildings. This perspective aligns with that of Brand (1995), who views buildings as intricate systems governed by the 'Shearing layers of change', a concept developed from Duffy's proposal (Duffy & Hannay, 1992). Accordingly, buildings are understood as layered structures in which time plays a pivotal role in the way they interact with each other and with the user. As Duffy stated, quoted in Brand (1995, p.12): “The unit of analysis for us isn’t the building, it’s the use of the building through time. Time is the essence of the real design problem.” This renders it necessary to go back to the building once finished and continue doing so throughout its lifecycle. The levels of POE The literature distinguishes between three ‘levels of effort’ at which POE can be conducted, which differ mainly in terms of the thoroughness and purpose of the assessment: indicative, investigative, and diagnostic (Hadjri & Crozier, 2009; Preiser, 1995; Sanni-Anibire et al., 2016). These levels vary in methods and the degree of engagement of researchers and participants, and encompassing the phases of planning, conducting and applying. They can be described briefly as follows: Indicative: This level provides a general assessment of the most important positive and negative aspects of the building from the users' point of view. It involves a brief data collection period, characterised by walk-throughs, interviews and survey questionnaires with occupants. It is not exhaustive and may reveal more complex problems that need to be addressed with an investigative or diagnostic POE. It can be completed in a few hours or days. Investigative: If a relevant problem identified in an indicative POE requires further research, an investigative POE is carried out. This second level implies a more robust amount of data to be collected, the use of more specialised methods, and possibly the disruption of occupants' routines and building use due to the prolonged engagement in the research endeavour. It can take weeks to months to complete. Diagnostic: This level is characterised by its approach which is both longitudinal and cross-sectional. It may involve one or more buildings and a research process that may take months to a year or more to complete. It is more akin to research conducted by specialised institutions or scholars. The scope can be very specific but also have sector-wide implications. Possible applications of the information gathered through POE A more recent review of the literature on POE studies highlights the variegated range of purposes behind it: impact of indoor environmental quality on occupants, design and well-being, testing of technologies, informing future decision-making or feedforward, and impact of building standards and green rating systems, to name a few (Boissonneault & Peters, 2023; Li et al., 2018). The breadth of applications and rationale for conducting POE studies show that it is a powerful tool for assessing a wide array of issues in the built and living environment, and partly explain the interest it holds for researchers. However, the industry is still lagging behind, which hinders the dissemination and further implementation of the findings and results.  More collaboration between academia and industry is therefore crucial as the great impact lies in applying POE and BPE as a structural part of the sector’s practice. Moreover, since POE primarily relies on fieldwork and the collection of empirical data, a more comprehensive assessment that incorporates mixed methods and a systematic approach can yield greater benefits for the entire building production chain. The collected feedback, analysis and resulting conclusions can create learning loops within organisations and bring about real changes in the lives of current and future building users. Therefore, a robust POE should be accompanied by the implementation of the concomitant action plan to address the problems identified. For this purpose, a theory of change approach can be helpful. In this sense, POE can become a very effective facility management tool (Preiser, 1995). Some examples of the varied uses of data provided by robust POE and BPE include the creation of databases for informed decision-making, benchmarking and integration into BIM protocols or GIS-powered tools. In this sense, generating data that can be compared and benchmarked is critical to the long-term impact and value for money of undertaking the activity. It is therefore imperative to recognise POE for its benefits rather than viewing it as a liability or a mere nice-to-have feature. On the other hand, POE inherently involves a wide range of disciplines within the built environment, including design, engineering, psychology, policy and finance, among others. This multidisciplinary aspect can be leveraged to promote transdisciplinary research to help better understand the relationships between buildings and people It delves into the impact of these relationships, considering human behaviour and well-being. This perspective is often referred to as the building performance-people performance paradigm, as denominated by other POE researchers (Boissonneault & Peters, 2023). Architectural geographers, for instance, have explored the various meanings and emotions ascribed by inhabitants to buildings, particularly council estates in the UK, through actor-network theory-informed research (Jacobs et al., 2008, 2016; Lees, 2001; Lees & Baxter, 2011). Similarly, the work of organisations such as the Quality of Life Foundation encompassed in the Quality of Life Framework (Morgan & Salih, 2023; URBED, 2021), has highlighted the link between the places where we live and its impact on our quality of life through systematic POEs conducted in collaboration with social housing providers and local authorities. Amid the climate emergency and the pressing need to curtail carbon emissions, there is now a need for the sector to innovate and mitigate the impact of building construction and operation. It has been argued that sustainability cannot be achieved only by adopting energy-efficient technologies or by promoting certifications such as LEED, Passivhaus, or assessment protocols such as BREEAM (Building Research Establishment Environmental Assessment Methodology). As discussed earlier, conducting these assessments is an effective tool to mitigate and solve the discrepancy between the expected energy performance of the designed building vis à vis that of its real-life counterpart, the so-called performance gap. POE can be used to ascertain the social performance gap by including qualitative and well-being-related indicators (Brown, 2018). In this way, buildings are evaluated not only in terms of their ability to comply with building regulations and environmental goals, but also in meeting social objectives in order to provide greater sustainability and affordability, particularly in housing.

A universal definition of social housing is difficult, as it is a country-specific and locally contextualised topic (Braga & Palvarini, 2013). This review of the concept focuses on social housing in the context of the UK from the late 1980s, which Malpass (2005) refers to as the phase of ‘restructuring the housing and welfare state’, to the early 2000s, known as the phase of the ‘new organisation of social housing’. In response to previous demands for housing, such as those arising during the Industrial Revolution, and recognising the persistent need to address the substandard quality of housing provided by private landlords in the UK (Scanlon et al., 2015), the primary objective of social housing has historically been to enhance the overall health conditions of workers and low-income populations (Malpass, 2014; Scanlon et al., 2015). However, this philanthropic approach to social housing changed after the Second World War when it became a key instrument to address the housing demand crisis. Private initiatives, housing associations, cooperatives and local governments then became responsible for providing social housing (Carswell, 2012; Scanlon et al., 2015). Social housing in the UK can be viewed from two perspectives: the legal and the academic (Granath Hansson & Lundgren, 2019). Along these two perspectives, social housing is often analysed based on four main criteria: the legal status of the landlord or provider, the tenancy system or tenure, the funding mechanism or subsidies, and the target group or beneficiaries (Braga & Palvarini, 2013; Carswell, 2012; Granath Hansson & Lundgren, 2019). From a legal perspective, social housing maintained its original goals of affordability and accessibility during the restructuring period in the late 1980s. However, citing the economic crisis, the responsibility for developing social housing shifted from local authorities to non-municipal providers with highly regulated practices aligned with the managerialist approach of the welfare state (Granath Hansson & Lundgren, 2019; Malpass, 2005; Malpass & Victory, 2010). Despite the several housing policy reviews and government changes, current definitions of social housing have maintained the same approach as during the restructuring period. Section 68 of the Housing and Regeneration Act 2008, updated in 2017, defines social housing as low-cost accommodation provided to people whose rental or ownership needs are not met by the commercial market (HoC, 2008; 2017, pp. 50-51). The Regulator of Social Housing, formerly the Homes and Communities Agency, has adopted the earlier definition of social housing and clarified which organisations provide it across the UK. These organisations include local authorities, not-for-profit housing associations, cooperatives, and for-profit organisations (RSH, 2021). In contrast, the National Housing Federation emphasises the affordability of social housing regardless of the type of tenure or provider (NHF, 2021). From an academic perspective, Malpass (2005) explains that during the restructuring phase, social housing was defined as a welfare-supported service – although it did have limitations, which meant that funding principles shifted from general subsidy to means-tested support for housing costs only, which later formed the basis for the Right to Buy Act introduced by the Thatcher government in the early 1980s (Malpass, 2005, 2008). The restructuring phase, however, came as a response to the housing 'bifurcation' process that began in the mid-1970s and accelerated sharply from the 1980s to 1990s (Kleinman et al., 1998; Malpass, 2005). During this phase, the role of social housing in the housing system was predominantly residual, with greater emphasis placed on market-based solutions, and social housing ownership concerned both local authorities and housing associations (Malpass & Victory, 2010). This mix has influenced the perception of social housing in the 'new organisation' phase as a framework that regulates public housing intervention for specific groups and focuses on enabling non-municipal providers (Malpass, 2005, 2008; Malpass & Victory, 2010). Currently, as Carswell (2012) explains, social housing plays an important role in nurturing a variety of initiatives aimed at providing ‘good-quality’ and ‘affordable’ housing for vulnerable and low-income groups (Carswell, 2012). Oyebanji (2014) sees social housing as any form of government-regulated housing provided by public institutions, including non-profit organisations (Oyebanji, 2014). Additionally, Bengtsson (2017) describes social housing as a system that aims to provide households with limited means, but only after their need has been confirmed through testing (Bengtsson, B, 2017 as cited in Granath Hansson & Lundgren, 2019). To a great extent, social housing in the UK can be seen as a service system that is intricately linked to the welfare state and influenced by political, economic, and social components. Despite being somehow determined by common factors and actors,  the relationship between social housing and the welfare state can sometimes be complex and subject to fluctuations (Malpass, 2008). In this context, the government plays a vital role in shaping and implementing the mechanisms and practices of social housing. While the pre-restructuring phase focused on meeting the needs of the people by increasing subsidies and introducing the right to buy (Stamsø, 2010), the aim of the restructuring phase was to meet the needs of the market by promoting economic growth (privatisation, market-oriented policies and reducing the role of local authorities) (Stamsø, 2010; Malpass, 2005) . The new organisational phase, on the other hand, works to meet and balance the needs of all, with people, politics and the economy becoming more intertwined. Welfare reform legislation passed in 2010 aims to enable people to meet their needs, but through 'responsible' subsidies, leading to a new policy stance that has been described as 'neoliberal' thinking (Hickman et al., 2018). However, there are still no strict legal requirements for the organisation and development of social housing as an independent service system, and most of the barriers to development are closely related to the political orientation of the government, rapid changes in housing policy and challenges arising from providers' perceptions of existing housing policy structures (Stasiak et al., 2021).

From the three pillars of sustainable development, economic, environmental and social, the latter  involving social equity and the sustainability of communities, has  been especially neglected. Ongoing problems caused by conflicting economic, environmental and social goals with regard to the processes of urbanisation continue. underpinning economic growth that contradict principles of environmental and social justice (Boström, 2012; Cuthill, 2010; Winston, 2009). Research on sustainable development highlights the need for further investigation of social sustainability (Murphy, 2012; Vallance et al., 2011). Social sustainability has been interpreted as an umbrella term encompassing many other related concepts; “social equity and justice, social capital, social cohesion, social exclusion, environmental justice, quality of life, and urban liveability” (Shirazi & Keivani, 2019, p. 4). A vast number of studies have been dedicated to defining social sustainability by developing theoretical frameworks and indicators particularly relevant to urban development and housing discourse (Cuthill, 2010; Dempsey et al., 2011; Murphy, 2012; Woodcraft, 2012). However, with a lack of consensus on the way of utilising these frameworks in a practical way, especially when applied to planning, social sustainability has remained difficult to evaluate or measure. Consequently, planning experts, housing providers and inhabitants alike understand social sustainability as a normative concept, according to established social norms, and less as an opportunity to critically examine existing institutions. Vallance et al (2011) provide three categories to analyse social sustainability, development, bridge and maintenance sustainability: (a) social development improves conditions of poverty and inequity, from the provision of basic needs to the redistribution of power to influence existing development paradigms; (b) the conditions necessary to bridge social with ecological sustainability, overcoming currently disconnected social and ecological concerns; and (c) the social practices, cultural preferences as well as the environments which are maintained over time. Maintenance social sustainability particularly deals with how people interpret what is to be maintained and includes “new housing developments, the layout of streets, open spaces, residential densities, the location of services, an awareness of habitual movements in place, and how they connect with housing cultures, preferences, practices and values, particularly those for low-density, suburban lifestyles” (Vallance et al., 2011, p. 345). Therefore, the notion of maintenance is especially important in defining social sustainability by directly investigating the established institutions, or “sets of norms” that constitute the social practices and rules, that in turn, affect responsibilities for planning urban spaces. A conceptual framework that appears frequently in social sustainability literature is that of Dempsey et al. (2011)⁠ following Bramley et al. (2009), defining social sustainability according to the variables of social equity and sustainability of community and their relationship to urban form, significantly at the local scale of the neighbourhood. In terms of the built environment, social equity (used interchangeably with social justice) is understood as the accessibility and equal opportunities to frequently used services, facilities, decent and affordable housing, and good public transport. In this description of local, as opposed to regional services, proximity and accessibility are important. Equitable access to such local services effectively connects housing to key aspects of everyday life and to the wider urban infrastructures that support it. Sustainability of community is associated with the abilities of society to develop networks of collective organisation and action and is dependent on social interaction. The associated term social capital has also been used extensively to describe social norms and networks that can be witnessed particularly at the community level to facilitate collective action (Woolcock, 2001, p. 70). They might include a diversity of issues such as resident interaction, reciprocity, cooperation and trust expressed by common exchanges between residents, civic engagement, lower crime rates and other positive neighbourhood qualities that are dependent on sharing a commitment to place (Foster, 2006; Putnam, 1995; Temkin & Rohe, 1998). In fact, “the heightened sense of ownership and belonging to a locale” is considered to encourage the development of social relations (Hamiduddin & Adelfio, 2019, p. 188). However, the gap between theoretical discussions about social sustainability and their practical application has continued. For example, the emphasis of social sustainability as a target outcome rather than as a process has been prioritised in technocratic approaches to planning new housing developments and to measuring their success by factors which are tangible and easier to count and audit. Private housing developers that deal with urban regeneration make bold claims to social sustainability yet profound questions are raised regarding the effects of gentrification (Dixon, 2019). Accordingly, the attempted methods of public participation as planning tools for integrating the ‘social’ have been found to be less effective - their potential being undercut due to the reality that decision-making power has remained at the top (Eizenberg & Jabareen, 2017). Therefore, social sustainability is not a fixed concept, it is contingent on the interdependence of the procedural aspects (how to achieve social sustainability) and substantive aspects (what are the outcomes of social sustainability goals) (Boström, 2012). From this point of view, social sustainability reveals its process-oriented nature and the need to establish processes of practicing social sustainability that begin with the participation of citizens in decision-making processes in producing equitable (i.e. socially sustainable) development. As a dimension of sustainable development that is harder to quantify than the economic or environmental aspects, the operationalisation of social sustainability goals into spatial, actionable principles has remained a burgeoning area of research. In such research, methods for enhancing citizen participation are a particularly important concern in order to engage and empower people with “non-expert” knowledge to collaborate with academic researchers.

Social value (SV) is a wide-ranging concept that encompasses the wider economic, social and environmental well-being impacts of a specific activity. Given its applicability across various sectors, diverse interpretations and definitions exist, often leading to its interchangeable use with other terms, such as social impact. This interchangeability makes it difficult to establish a universally accepted definition that satisfies all stakeholders, contributing to the term’s adaptability and to a variety of methods for identification, monitoring, measurement and demonstration. Nevertheless, common themes emerge from literature definitions. First, SV involves maximizing benefits for communities and society beyond an organisation's primary goals, which requires innovation and a focus that goes beyond financial values. It is often referred to as the added value of an intervention. Second, the short-, medium- and long-term effects of activities, as well as their broader community reach, need to be assessed in terms of a life-cycle project perspective. Thirdly, SV aligns with the triple bottom line of sustainability, which underlines social, environmental and economic considerations in well-being. In the UK, SV gained prominence with the introduction of the Public Services (Social Value) Act 2012. This legislation mandates organisations commissioning public services to consider and account for the wider impacts of their operations (UK Government 2012; UKGBC, 2020, 2021). The Act has provided incentives to quantitatively measure the impact of projects on communities and standardise approaches in the built environment, a sector that has been significantly influenced by this regulatory framework. Organisations such as the UK Green Building Council (UKGBC) have played a crucial role in shaping a common agenda through reports such as Delivering Social Value: Measurement (2020) and Framework for Defining Social Value (2021), which set out the steps needed to determine social value. Recognising that SV is strongly influenced by contextual factors, these publications emphasize the challenge for formulating an all-encompassing definition. Instead, they advocate for focusing efforts on developing context-specific steps and methods for measurement.     However, the existing literature is mainly concerned with SV during the procurement and construction phases, overlooking the SV of buildings during the use phase and the potential opportunities and benefits they offer to users. This bias is due to the construction sector's rapid response to the Act and its easier access to certain types of information. This influences the prominence of certain data in project’s impact assessments and SV reports, such as employment opportunities, training, placements, and support of local supply chains through procurement. More intangible outcomes such as community cohesion, quality of life improvements, enhanced social capital, cultural preservation, empowerment and long-term social benefits are rarely featured as they are deemed more challenging to quantify due to their subjective or qualitative nature. Similarly, there remains a lack of clarity and consensus regarding a standardised approach to assessing the added value created. The challenge stems from diverse interpretations of value among stakeholders, influenced by their unique interests and activities. Communicating something inherently subjective becomes particularly daunting due to these varying perspectives. Additionally, translating all outcomes into financial metrics is also problematic. This is primarily due to the unique circumstances that characterise each development and community, making it impractical to hastily establish targets and universal benchmarks for their assessment. (Raiden et al., 2018; Raiden & King, 2021a, 2023). This complexity is recognised by Social Value UK (2023: n.p.), stating: “Social value is a broader understanding of value. It moves beyond using money as the main indicator of value, instead putting the emphasis on engaging people to understand the impact of decisions on their lives.” Moreover, the growing significance and momentum that SV is gaining are evident in the emergence of analogous legislations that have appeared in recent years and that have a direct influence on shaping how the built environment sector operates in their respective countries. Noteworthy examples of social value-related regulations include the Well-being of Future Generations Act 2015 in Wales; the Procurement Reform Act 2014 in Scotland; the social procurement frameworks in Australia; the Community Benefit Agreements in Canada; the Government Procurement Rules in New Zealand; and the Environmental, Social, and Governance (ESG) criteria considered in various countries around the world, among others.   Identifying and measuring social value SV should be an integral aspect of project development and, therefore, must be considered from the early stages of its conception, taking into account the entire lifecycle. The literature highlights a three-step process for this: 1) identifying stakeholders, 2) understanding their interests, and 3) agreeing on intended outcomes (UKGBC 2020, 2021). More recently, Raiden & King (2021b) linked the creation of SV to the achievement of the United Nations Sustainable Development Goals (SDGs). In the context of the built environment, SV can contribute to reporting on the SDGs, elevating the value the sector creates to society onto the international agenda (Caprotti et al., 2017; United Nations, 2017). While SDG 11 “Make cities and human settlements inclusive, safe, resilient and sustainable”, is often placed within the remit of the built environment, SV programmes developed by social housing providers, for example, extend the sector’s impact beyond SDG 11, covering a broader range of areas  (Clarion Housing Group, 2023; Peabody, 2023). This aspect is also echoed in the Royal Institute of British Architects (RIBA) Sustainable Outcomes Guide, which links the SDGs to specific outcomes, including the creation of SV (Clark & HOK, 2019). Over the past decade, various methodologies have been proposed to undertake the intricate task of assessing value beyond financial metrics, drawing inspiration from the work of social enterprises. Among the most prominent and widely adopted by diverse stakeholders in the sector are the Social Return on Investment (SROI), Cost-Benefit Analysis (CBA) — sometimes referred to as SCBA when given the social epithet—, and the well-being valuation approach. (Fujiwara & Campbell, 2011; Trotter et al., 2014; Watson et al., 2016; Watson & Whitley, 2017). The widespread implementation of these approaches can be explained by the development of tools such as the UK Social Value Bank, linked to the well-being valuation method. This tool, used to monetise ‘social impacts’, is endorsed by influential stakeholders in the UK’s housing sector, including HACT (2023), or the Social Value Portal and National TOMs (Themes, Outcomes and Measures) (Social Value Portal 2023). In the measuring of SV, these methodologies unanimously emphasize the importance of avoiding overclaiming or double-counting outcomes and discounting the so-called deadweight, which refers to the value that would have been created anyway if the intervention had not taken place, either through inertia or the actions of other actors. While the development of these approaches to measuring SV is pivotal for advancing the social value agenda, some critics contend that there is an imbalance in presenting easily quantifiable outcomes, such as the number of apprenticeships and jobs created, compared to the long-term impact on the lives of residents and communities affected by projects. This discrepancy arises because these easily quantifiable metrics are relatively simpler to convert into financial estimates. Steve Taylor (2021), in an article for The Developer, pointed out that the methods employed to measure social value, coupled with the excessive attention given to monetisation and assigning financial proxy values to everything, may come at the expense of playing down the bearing of hard-to-measure well-being outcomes: “As long as measurement of social value is forced into the economist’s straightjacket of cost-benefit analysis, such disconnects will persist. The alternative is to ask what outcomes people and communities actually want to see, to incorporate their own experiences and perspectives, increase the weighting of qualitative outcomes and wrap up data in narratives that show, holistically, how the pieces fit together. We loosen the constraints of monetisation by mitigating the fixed sense of value as a noun; switching focus to its role as an active verb – to ‘value’ – measuring what people impacted by changes to their built environment consider important or beneficial.” The process of comprehensively measuring and reporting on SV can be challenging, time-consuming and resource-intensive. It is therefore important that stakeholders truly understand the importance of this endeavour and appreciate the responsibilities it entails. Recently, Raiden and King (2021a, 2023) have highlighted the use of a mixed-methods approach for assessing SV, proposing it as a strategy that can offer a more thorough understanding of the contributions of actors in the field. They argue that an assessment incorporating qualitative methods alongside the already utilized quantitative methods can provide a better picture of the added value created by the sector. These advancements contribute to the overarching goal of showcasing value and tracking the effects of investments and initiatives on people's well-being. Nevertheless, a lingering question persists regarding the feasibility of converting all outcomes into monetary values. Social value in architecture and housing design In the field of architecture, the RIBA, in collaboration with the University of Reading, took a significant step by publishing the Social Value Toolkit for Architecture (Samuel, 2020). This document provides a set of recommendations and examples, emphasizing why architects should consider the SV they create and providing guidance on how to identify and evaluate projects, incorporating techniques such as Post-Occupancy Evaluation. This is a remarkable first step in involving architects in the SV debate and drawing attention to the importance of design and the role of architecture in creating value (Samuel, 2018). More recently, Samuel (2022:76) proposed a definition of SV in housing that places the well-being of residents at the centre of the discussion. Accordingly, SV lies in “fostering positive emotions, whether through connections with nature or offering opportunities for an active lifestyle, connecting people and the environment in appropriate ways, and providing freedom and flexibility to pursue different lifestyles (autonomy).” In this context, it is also relevant to highlight the work of the Quality of Life Foundation (QoLF) & URBED, who published The Quality of Life Framework (URBED, 2021). This evidence-based framework identifies six themes in the built environment crucial for assessing relationships between places and people:  control, health, nature, wonder, movement, and community. More recently, Dissart & Ricaurte (2023) have proposed the capability approach as a more comprehensive conceptual basis for the SV of housing. This approach expands the work of the QoLF, focusing the discussion on the effective freedoms and opportunities that the built environment, specifically housing, offers its inhabitants. It serves as a means to gauge the effectiveness of housing solutions and construe SV.