Delivering human-centred housing: understanding the role of post-occupancy evaluation and customer feedback in traditional and innovative social housebuilding in England

Abstract Housing shortages and construction delays characterize the current UK housing crisis, and housing need is not met. Modern methods of construction (MMC) are put forward as a solution to ensure quicker, safer, and greener delivery of new homes and are supported by the government, especially in the social housing sector. The paper explores the post-occupancy evaluation mechanisms used by housing associations delivering homes with traditional and MMC approaches. It argues that, alongside the digital and offsite transformation of housebuilding, the industry needs to reconsider the way customer feedback is collected and what purposes it serves. The paper argues that UK housebuilding in the social housing sector can benefit from re-purposing post-occupancy evaluation (POE) from only measuring customer satisfaction and detecting defects, which is currently the case, to using it to improve housing design and construction quality. This could be done by developing a systematic learning loop from residents of previous projects to the design, development, and construction teams across the housebuilding supply chain. It could particularly benefit housing associations pioneering MMC that, as long-term asset holders of developed houses, have a vested interest in improving the quality of homes and creating a better residential experience. The accumulated knowledge of such customer-centred approaches could also inform MMC technology development and help increase its uptake. However, as the paper further discusses, there are many challenges on the way to effective POE in social housing provision, including the nature of the MMC-based housebuilding supply chain and the industry’s structural factors.


Introduction
The housebuilding industry in the UK is often criticized for inefficiencies in addressing housing needs, slowness in delivering new homes, and for poor housing quality (Burgess et al. 2020, MHCLG 2020a. The ongoing attempts to address these problems have been mostly technocentric, with heavy reliance on digitalization and manufacturing approaches in construction that could help improve industry productivity and deliver homes quickly and at a potentially cheaper cost (Maslova et al. 2021). Against this backdrop, feedback about delivered projects is often overlooked. However, considering building performance and addressing customers' needs is essential for a customer-focussed, or humancentred, approach to housing design and construction (Orihuela and Orihuela 2014, Eggen et al. 2016, Agee et al. 2021 instead of one that is heavily technocratic.
The customer experience of, and satisfaction with, new build homes in the UK housebuilding industry is assessed predominantly using post-occupancy evaluation (POE). Originating from the US, POE was introduced to appraise the performance of buildings after they have been handed over and are occupied (Durosaiye et al. 2019). Evidence shows that POE is not being effectively implemented as a standard practice across the construction industry (Bordass 2003, Palmer et al. 2016) and, where practical research on POE is carried out, it tends to be mostly quantitative (Parn et al. 2015) and lacks qualitative depth, particularly around the exploration of the reasons behind the low take-up of POE in the industry. Traditionally, POE has been used to establish user satisfaction alongside certain pre-set technical criteria that a new build is expected to meet. In particular, it has proven effective in exploring cause-effect relationships between technical features of the building and user experiences and needs (Kim et al. 2013). However, over time, a wider understanding of POE came into use, consisting of two parts: (1) the process of evaluating building performance and quality in design and construction; and (2) the loop of learning from previous projects, disseminating accumulated knowledge and improving future processes and practices (Designing Buildings 2016, Hay et al. 2018. This understanding of POE in construction has similarities with a user-centred design approach adopted by other industries. In particular, the basic principles of human-centred design include the central and participative role of the user in "an iterative design process, as well as the identification of user-specific factors to guide and assess the design" (Eggen et al. 2016, p. 2). In the fast-paced, competitive setting of a digitalizing world, industries from travel to manufacturing have transformed their processes and organizational structures, moving towards agile and iterative project approaches. The rise of Big Data companies, Internet of Things, e-governance, and e-learning are all evidence of the same direction of transformation. Effective user experience research has become an integral part of their production cycle and it allows for the testing of design prototypes and for tailoring to ensure the end product is designed to meet user needs (Gothelf and Seiden 2016). By capturing realtime user data, feedback loops from users inform product design and development which continuously modernize together with evolving user needs. The demand-driven nature of their businesses creates competition and, therefore, willingness to constantly improve the design quality of products.
This study brings into focus the role of customer experience and POE in the social housebuilding sector in England. It explores whether the sector could (and needs to) learn from other industries and benefit from actively using user experience in more agile production and iterative design processes. Indeed, a customercentric approach could be particularly important in the light of the digital and technological transformation that the housebuilding industry in the UK is currently undergoing (Burgess et al. 2020). There is an understanding that an increased use of Modern Methods of Construction (MMC) could improve industry efficiency and build quality, and could also bring environmental and aesthetic benefits (NHBC 2018, 2019, MHCLG 2019. MMC is an umbrella term for a broad range of manufacturing techniques used as an alternative to traditional construction methods in the UK (NHBC 2018) and can be defined as "forms of offsite manufacture for construction, including modular and panellized systems, and timber or steel framed homes" (House of Commons 2019, p. 14). While the MMC framework includes seven categories, the first three categories of MMC have the highest pre-manufactured value and receive most of the government's support: 1-3D primary structural systems; 2-2D primary structural systems; 3-non-systemized structural components (MHCLG 2019). Here, and later in the paper, MMC-based housebuilding refers to the use of high categories of MMC, i.e. categories 1-3.
MMC-based housebuilding is at the core of a package of technical measures designed to tackle the housing crisis in the UK, and a growing number of housebuilders, particularly social housing providers, are involved in its adoption (Farmer 2016, MHCLG 2020a. One of the barriers to the uptake of MMC is associated with the negative public perception of "factory-made" homes due to its post-World War II history in the UK (NHBC 2020). However, some evidence suggests that the barriers to prefabrication are associated with the negative attitudes amongst lenders and insurers rather than consumers (Laing et al. 2001, Craig et al. 2005 and are reinforced by the developers' and architects' perceptions of consumer views: "Resistance to prefabrication is a complex function of both rational and ill-considered biases amongst the full range of groups involved in housing provision: from developers to professionals to clients to housing purchasers" (Edge et al. 2002). Considering this trajectory of modernizing UK housebuilding towards a manufacturing-led construction approach and the associated transformation of traditional construction models, the question arises as to whether the processes of engaging with customers and collecting feedback also require modernization. To spotlight this question, this paper explores the current role played by POE in UK housebuilding practices in social housing provision, gaps in the feedback loop within the supply chain, and discusses the benefits and barriers to advancing and embedding POE across the housebuilding industry as it seeks to make greater use of MMC.
To examine the role of customer experience and post-occupancy evaluation, the research focussed on housing associations as the most resident-focussed housebuilders. Housing in the UK is built by three major sectors: private enterprise, housing associations, and local authorities. Volume housebuilders belonging to the first sector deliver homes direct to the market and are profit-driven. Housing associations in the UK are social housing providers that operate on a not-for-profit model; however, some social housing providers also deliver for-profit housing to cross-subsidize affordable housebuilding. Together, housing associations and local authorities build around 20% of all new dwellings in the UK, accounting for 42,100 homes in 2019 (ONS 2021). A particular feature that distinguishes housing associations from other housebuilders is that they not only develop and build new homes, they are also long-term asset managers of many of those homes. As a result, they have a vested interest in improving their housing product to prevent complaints, reduce the work needed to rectify defects, and reduce maintenance needs and operating costs (such as energy costs) in the long term. Thus, this group of housebuilders holds the most interest in understanding customer experience and is best suited for this qualitative study. In-depth interviews were conducted in the UK in 2021 with housing associations using both traditional construction methods and MMC, MMC-manufacturers, industry experts, and architects. Questions revolved around the feedback loop, existing practices of post-occupancy evaluation, and integration of customer experience. Through purposive sampling (Patton 2002), this study analyzed the existing systems of interaction between customers and housing associations and across the MMC housebuilding supply chain in the provision of social housing.
Given the government-and industry-drive for transformation from traditional to high-category MMCbased delivery of homes, as well as the need to improve build quality, generate knowledge based on building performance, and overcome resistance to prefabrication among lenders, insurers, and other industry actors, the paper opens a discussion of whether customer-centred housebuilding could provide a solution and explores the role that effective and timely POE may play in this transformation agenda.

Post-occupancy evaluation and customer satisfaction in housebuilding
In the academic and professional literature on the built environment, the benefits and importance of POE for the improvement of processes and practices in construction have been widely researched (Bordass 2003, Becker 2018, Hay et al. 2018, Durosaiye et al. 2019. Many studies explored the relationship between building design and performance and the occupants of the building (Kim et al. 2013, Jones and Grigoriou 2014, Amasyali and El-Gohary 2016, Watson et al. 2016, the value of using POE (Macmillan 2004, Hay et al. 2018, and various POE methodologies (e.g. Preiser and Nasar 2007, Leaman et al. 2010, RIBA 2016, including quantitative and qualitative approaches (e.g. Preiser 2001, Bordass 2003, Macmillan 2004, Leaman et al. 2010, Becker 2018, Hay et al. 2018. Although the post-occupancy agenda is wellestablished and it is recognized that POE is of tangible value to housebuilders, architects, the construction industry, residents, and wider society (Hay et al. 2017), questions about the practical use and efficiency of POE have remained open for a long time (Cooper 2001, Hay et al. 2018. First introduced by the Royal Institute of British Architects (RIBA) over 50 years ago, POE continues to exist as "a scanty endeavour of research-oriented academics, rather than being an embedded practice in the building procurement process in the UK" (Durosaiye et al. 2019, p. 347).
Hitherto, the basic indicator that POE has typically been used to measure is customer satisfaction, which can be defined as a feeling of pleasure or disappointment resulting from a comparison of the perceived performance of a product or service with the customer's expectations (Kotler 1996). Similarly, Parasuraman et al. (1985) argue that service quality and customer satisfaction are determined by "the discrepancy between expectations and perceptions" (p. 43). The drivers of customer satisfaction lie in "tangible evidence", relating to the actual performance of a service or a product. As evidence from a US-based survey of housing customers showed, the determinants of customer satisfaction rates among housebuilders were sales and support issues (relating to the work of sales staff and after-sales care), and product-related factors (including workmanship quality and house design) (Power 2000). Satisfaction rates are typically measured through surveys and represent a quantitative evaluation of the build quality and customer service. In the UK, volume housebuilders systematically collect customer satisfaction data across the private market, and it consistently shows high satisfaction rates. As the National New Homes Customer Satisfaction Survey of UK housebuilders showed in 2021, 91% of customers would "recommend their builder to a friend", which is the key question that customer satisfaction ratings are built on (HBF 2021, p. 1). However, customer satisfaction surveys do not provide qualitative insights about residential experience or details of what contributed to such evaluation scores.
Although it is argued that many of the building performance indicators are quantifiable-such as lighting, heat insulation, acoustics, humidity, ventilation, air tightness-as noted by Preiser (2001), a building might demonstrate excellent quantitative indicators while its occupants are not satisfied or comfortable using the building. Against this backdrop, POE as an approach has advanced to examine the performance of a building through user satisfaction by defining ways to "improve building design, performance and fitness for purpose through the systematic evaluation of the buildings in use, from the perspective of the people who use them" (Turpin-Brooks and Viccars 2006, p. 178). POE can demonstrate the actual use of spaces by occupants, the perceived quality of housing, or occupants' subjective comfort, which do not necessarily correlate with technical indicators of building performance (Durosaiye et al. 2019).
However, despite the well-researched benefits of a wider approach to POE, the culture of evaluating the performance of a building after it has been built and occupied by users for a while has not yet been successfully embedded into the design and procurement process (Durosaiye et al. 2019). Among the key challenges hampering customer-focussed housing, studies highlight issues around communication and cooperation within the housebuilding company and between the company and its customers (Ozaki 2003). Good information flows between customers, housebuilders and design teams allow for the inclusion of customer requirements and preferences into the design and construction of the house in the most appropriate way. However, active communication with end-users has not been an active priority for housebuilders or their design, construction, and decision-making teams (Bordass 2003, Palmer et al. 2016. Some research also argues that omitting the collation of customer feedback can lead to misalignment between actual customer needs and the architects, engineering, and construction professionals' perception of customer needs (Agee et al. 2021). Furthermore, Ozaki (2003) showed that, even when customer feedback around motivations not to buy a house was repeatedly collected in some housebuilding companies, it still did not reach the head office or design teams because there was no formal channel to communicate between marketing and front-end sales divisions. Developing improved communication and a loop of learning, not only between the end-customers and the housebuilder but also within the housebuilding company and with contractors, is considered essential to enable effective POE.
Customers communicate their preferences in different ways, including desires and needs, suggestions towards product solutions, and even as requests for radical changes (Hentschke et al. 2020). As Piller et al. (2004) found, if customer needs and preferences are translated into product requirements, it is possible for companies to convert subjective information into explicit knowledge. This knowledge can be used to better understand customer demands, inspire new developments, introduce innovations and also provide guidance on whether to limit or expand product variety. It is worth noting that, by contrast, neglecting customer preferences and needs might lead to failures in the business: Ozaki (2003) gave examples of how ignorance of a customer preference for the privacy of personal space led to difficulties selling houses built with bedrooms on the ground floor. However, it is worth emphasizing that customers have the opportunity to "vote with their wallets" in an open market with sufficient housing supply and diversity, but less so when the open housing market faces shortages, as is the case in the UK. The UK new-build housing market is not customer-led, a shortage of supply constrains choice and customers are bound to purchase homes that the market offers and make compromises against their own preferences and needs.
Traditionally, the success of a project in the housebuilding sector has been measured through cost, time, quality, and scope meaning that houses delivered within the deadline, the budget, and according to technical specifications are deemed successful (Orihuela and Orihuela 2014). In adopting this approach, residents have little or no voice in making decisions as to where and what types of housing should be built (Al-Momani 2003) and are largely seen as customers who buy the product at the end of the construction process and thus have a minimal role after purchase. However, some government-subsidized housing developers, such as UK housing associations (who build and provide social housing) have mixed interests that combine profitable economic models and social value to address the needs of certain groups of tenants. The role of residential experience in the social housing sector is particularly important as housing delivery is viewed as a service. In their UKbased study, Sagoo and Khalfan (2017) list numerous factors that affect customer expectations in social housing, such as the quality of accommodation, fair rent, value for money, services, and the quality of repairs undertaken either as part of day-to-day repairs or in the form of planned maintenance. Social housing providers, therefore, have greater motivation to adopt tailor-made housing services to meet the varying needs of their service users (social and affordable housing tenants), including during the housebuilding, management, and maintenance stages (ibid). The pioneering role of social housing providers in customerfocussed housing delivery in the UK is also determined by specific recommendations from the government to procure new housing using customer satisfaction indicators (product, service, and indicators related to defects) which create additional incentives for social housing providers (Barlow and Ozaki 2003).

Context: transformation agenda of the UK housebuilding industry
In the UK, the construction of residential homes is driven by a housing shortage that fails to meet the high demand for new homes. The undersupply of housing contributes to making homes less affordable while the design and build quality of built homes are given less consideration. As Burgess et al. (2020) highlight, housing represents 53% of all repair and maintenance work by value (ONS 2019), and the National House Building Council (NHBC) pays £85m annually to rectify defects in new build homes (NHBC 2019). Driven by government ambitions, improving the quality and cost of new housing has become an aspiration of the UK housebuilding industry, facilitated by increased use of MMC.
A transformational shift from conventional housebuilding towards innovative approaches has been called for in an Industrial Strategy (HM Government 2018) and this "should provide benefits across the design, construction, management and maintenance of housing in the UK" (Burgess et al. 2020, p. 4). Transformation in housebuilding is taking place along two main fronts, namely, digitalization and manufacturing-led construction. The former relates to the development of digital technologies in construction, such as Building Information Modelling (BIM), that help to detect and eliminate design problems in the virtual environment, preventing reworking on-site (Burgess et al. 2020). Manufacturing approaches to construction are undergoing transformation, and this front embraces offsite construction, modular housing, and other innovations that, in the UK, are broadly referred to as modern methods of construction. By using innovations and offsite solutions, MMC housebuilding is associated with numerous benefits, such as faster construction speed, material efficiency, reduced waste, higher fabrication quality, reduced local disruption, and others (Maslova et al. 2021). One of the key advantages of MMC-based housing is that it can improve the overall quality of the end product. The adoption of high categories of MMC with high pre-manufactured value is incentivized across the industry, especially in the social housing sector. As such, the Affordable Homes Programme 2021-2026 not only has a condition for Strategic Partnership Grants to deliver a quarter of new homes using MMC but also that they meet a requirement for a pre-manufactured value of 55% or more (MHCLG & Homes England 2020), making highcategory MMC a priority. However, these innovations in the construction sector largely relate to the technical side of the industry and to the supply chain and do not typically target customers or their needs (Oti-Sarpong et al. 2022), reinforcing the technocratic nature of the ongoing industry transformation.
At the same time, recent government initiatives have given more thought to housing design and quality and stress the central role that users should play. A recent government policy document (MHCLG 2020a) has expressed the view that in the current planning system in England, "quality can be negotiated away too readily and the lived experience of the consumer ignored too readily" (p. 13)-there is a need for "a higher regard for quality, design and local vernacular" (p. 8). Similarly, there is a need to consider the aesthetic and environmental characteristics of new housing (Building Better, Building Beautiful Commission 2020, MHCLG 2020a). One of the suggested principles of the Building Better, Building Beautiful Commission relates to engagement with users: "The aim is not simply to seek user/community acceptance but to aim for an active contribution throughout" (Building Better, Building Beautiful Commission 2020, p. 162). Whereas social housing providers already focus on residents and their needs, the recent Social Housing White Paper (MHCLG 2020b, p. 2) calls for further actions to bring forward the voices of residents of social housing to ensure they "are safe, are listened to, live in good quality homes, and have access to redress when things go wrong". Hence, considering the numerous policies that allow greater space for a customer-centric approach, a better understanding is needed in terms of the role that users can have in the transformation agenda in UK housebuilding and the aspiration to improve housing quality. This study contributes towards filling this gap.

Methods
The study adopted a qualitative approach given the research objective of gaining a deeper understanding of the processes of post-occupancy evaluation and the relative novelty of the use of MMC technologies in social housebuilding. The initial study involved exploratory interviews with several actors in the UK housebuilding industry, including industry experts, representatives of collaboration platforms, and architects working with MMC solutions. It became apparent from three initial interviews that, compared to other housebuilders, housing associations have a greater interest in improving housing quality and working with customer experience due to the nature of their work in the affordable housing sector. Moreover, given the increasing use of MMC in the sector, it was deemed appropriate to include the views of manufacturers supplying housing solutions to this category of housebuilders. Further interviews and secondary data analysis reaffirmed the focus of the study on the social housebuilding supply chain. Housing associations, as social housing providers, are the recipients of public subsidies for affordable homes where housing delivery is tied to the need to increase the use of highcategory MMC. In line with the UK Government's commitment to foster innovative housebuilding, the Affordable Homes Programme for 2021-2026 enables housing associations to enter Strategic Partnerships and commit to delivering at least 25% of homes through MMC (MHCLG & Homes England 2020). Furthermore, as the long-term asset managers of newly-built homes, housing associations are motivated to ensure long-lasting performance and a better perceived quality of their homes, as well as conformity to residents' needs, when compared to other housebuilders.
Data collection took place between February and July 2021 and included 15 in-depth interviews carried out with two key groups of research participants: representatives of housing associations (eight interviews) and representatives of MMC manufacturers supplying housing solutions to housing associations (seven interviews). The study targeted housing associations delivering homes across multiple regions across England, including London, the South East, the South West, the East of England, the North West, and the North of England. The manufacturers interviewed supplied high-category MMC products (volumetric, modular, panellized systems, timber and steel frames, roof and floor solutions) to housing associations. Their perspectives complemented the data from housing associations and allowed the consideration of customer feedback loops across the supply chain. Interviewees' companies varied in terms of the portfolio size of their built projects and the length of their journey using MMC in construction. The selected interviewees held decision-making roles and included development directors, heads of performance and design teams, planning and technical directors, and leaders on MMC uptake. They were identified and approached as those in charge of customer engagement, design, and development in their organizations. All 15 interviewees had significant years of experience (ranging from 10 to over 30 years) working across the supply chain, using both traditional and MMC approaches in various building projects across the UK; this positioned them as industry experts, suitable for purposive sampling (Patton 2002). When saturation was reached, data collection was completed (see Guest et al. 2006). This study adopted purposive targeting of experts with knowledge in a particular field, which follows an established practice in qualitative research. As Guest et al.'s (2006) findings on saturation and generalizability in research show, "small samples can be quite sufficient in providing complete and accurate information within a particular cultural context, as long as the participants possess a certain degree of expertise about the domain of inquiry" (p. 74).
The interviews were carried out virtually through MS Teams and lasted between 30 and 90 min. All interviewees provided informed consent to participate in the study. Questions were open-ended, and structured around experiences with POE and the current organization of the feedback loop; forms of engagement with customers, its stages and main actors, required skills; and practical issues with performing design and construction changes to the housing product. The interviews were recorded, subsequently transcribed, anonymized, and analyzed thematically.
In addition to the interviews, the study also draws insights from secondary materials, such as reports, webpages, and customer guidance documents from the interviewees' organizations, government, and the wider housebuilding industry.

POE and feedback currently collected from residents
Given that housing associations are likely to be motivated to be the most innovative housebuilders when it comes to customer engagement, we explore, firstly, how POE is currently implemented in their organizations and what it is being used for. The housing associations interviewed were at the beginning of their journey using MMC, and their approach to collecting customer feedback was therefore established for traditionally built homes and typically included two stages. Firstly, information is collected from residents within the first 4-8 weeks of moving into a home. This is typically a short survey dedicated to aftercare and the identification of defects. Secondly, a wider survey is sent out to residents around 9-12 months after their move-in date. Interview participants confirmed that these two surveys represent a standard practice for POE among social housing providers and by housebuilders in the industry more generally. One of the participants identified the rationale behind the second home satisfaction survey as the following: The wider residents would get the new home satisfaction [form] around the 9-month mark. That's because we found if we do it when they first move in, everybody's delighted and you get this skewed result. And then if you do it around the 12 months mark, you just get a lot of responses around their defects and their experiences around that, and that's not what we're looking for. (Head of Development, HA) Notably, all but one of the interviewed housing associations reported that a similar two-stage POE was in place in their organization, with one carrying out a third survey around 2 years after the handover of keys. However, it became evident from the interviews that no further systematic feedback on residential experience or housing design and quality is collected in the subsequent years of occupancy. While the focus on collecting customer feedback in the first year after delivery is seen as sufficient to measure customer satisfaction in the traditional housebuilding setting, for housing associations striving to pioneer MMC-build homes, as some interviewees affirmed, longer-term engagement with residential experience might be needed. As long-term asset holders with different social tenants living in their properties over time, they could benefit from regularly collected feedback from tenants who move into the house in subsequent years as future tenants might experience living in the same property differently or new details about housing quality may develop over time. Furthermore, since MMC-based housebuilding is reliant on technologies, the performance and usability of which have not yet been tested in the long-run, collecting systematic data from users has the potential to support and ensure the longevity of housing quality, and it could also generate an evidence base which might be helpful in overcoming barriers to housing prefabrication.
The next consideration is related to the level of detail that the current POE generates. As reported in the interviews, questions typically asked in the customer surveys focus primarily on customer satisfaction (e.g. "How satisfied are you with your new home?"), the perceived comfort of home ("How do you find living in your home?"), energy efficiency ("Is the running cost of the home in line with your expectations?") and experiences of interactions with sales and aftercare divisions of the company ("How satisfied you are with the company? Have you reported any issues?"). The feedback forms rarely included questions about housing design (if they did, they related to layouts and kitchens) or construction quality (e.g. materials used, air tightness, robustness of finish), nor did they ask for suggestions for improvement. One interviewee, for example, noted that, compared to the private sector, one of the challenges of the social housing sector is that they can ask only one or a few questions in the customer surveys which they can then "benchmark against other people" (Director of Development, HA) because they do not have resources for collecting and analyzing more feedback. Another interviewee added that questions are not typically well-worded; they gain little insight from them and use them mostly for customer satisfaction metrics. Some housing associations observed that they found questions about designs in customer surveys ineffective: We have tried to put in a few design-based questions in the past … what we find is that the level of detail that you get back isn't always that useful because of the level of knowledge of the customer group. So we do ask a question about layouts, but we don't ask a wider question about design anymore. (Head of Performance, HA) Overall, the interviews suggested that using customer surveys as an approach to POE serves the purpose of portraying a good general picture of customer satisfaction, but is more limited in terms of understanding the experience of residents, given that the level of detail collected does not go much beyond statistical parameters: You'll get the satisfaction stats and you'll get some short comments associated with them. The usefulness of that detail can sometimes be a challenge. (Head of Performance, HA).
However, the study also found that, on occasions, additional resident feedback might be collected by housing associations regarding particular issues. In these cases, a smaller sample of residents is approached to carry out "touch points", focus groups, or specific customer surveys. Such engagement typically happens with customer panels made up of customers who had volunteered to take part in further surveys. Some interviewees also noted that given that customer panels tend to consist of a limited number of residents whose opinion has been collected for many years, they include fewer residents of MMC-build homes which are relatively new additions to their housebuilding portfolio.
If we have a question, we have these involved customers who we can go to with any questions and say, you know, we're thinking of changing our tenancy lets or … we are thinking about changing the way that we design things. And in the past, we have gone to them on a couple of different issues and got that sort of feedback. But it is not something that we do regularly in the same way that we do customer surveys. (Head of Performance, HA) These involved residents tend to be consulted about changes to housing designs or redevelopment. As one of the interviewees reported, resident participation and co-creation activities seem to be used more for regeneration projects rather than for new housing developments: In regeneration projects, we invite them [customers] into the room with the people that are on the project, and talk about the approach and the design ethos, and get that balanced view (Head of Design & Innovation, HA) However, the same interviewee added that such customer-focussed input is only taken from existing customers who will be rehoused on the same regeneration site but not in new-built homes.
Another issue that emerged from the interviews is the limited resources available in the social housing sector for customer engagement, something which prevents many housing associations from scaling up customer experience research. Few of the housing associations interviewed had trialled customer experience research on residents of MMC-build homes. While larger housing associations might have the resources to collect and analyze more detailed customer data, relevant interviewees reported that they tend to mostly rely on feedback from residents living in traditional-build homes because their uptake of MMC in housebuilding is still limited. Meanwhile, the interviewees from those smaller housing associations that do have a higher share of MMC-build homes in their portfolio reported that they collect only a basic level of feedback from residents; because of their smaller scale, their system of resident interaction and collection of customer feedback is limited to addressing key performance indicators (KPIs) on defects and customer satisfaction and is necessarily superficial in nature. Some interviewees from this latter category noted that they do not have the resources to analyze and integrate collected data. As a result of such limitations, in both categories, the voices of residents of MMC-build homes have limited representation and detail in the spectrum of customer feedback collected.
A further limitation on customer research by housing associations is linked to difficulties in engaging residents in such initiatives. Some interviewees reported that they tested episodic customer feedback with a greater level of detail, but found it ineffective as their findings did not reveal much as customers were reluctant to provide feedback: We did do a little bit of post-occupancy, qualitative research. But it was a very small pool, I would say. We probably only had a handful of returns. The customers haven't been that bothered about engaging with us, although we have tried. And, actually most of them, the ones who have engaged, have been positive: you know, "house feels warm" and things like that. (Planning and Technical Director, HA) The interviews also showed shared concern about over-burdening residents. As such, access to customers is rather limited and formalized by existing customer feedback surveys: There's that sensitivity with our customer service team … we don't want to bombard our customers with too [many requests for] feedback, because they'll switch off completely. (Head of Design and Innovation, HA) Additionally, the interviews reflected the fact that one of the specificities of working with social housing residents is that customers might be hesitant or reluctant to provide feedback on faulty elements of the property because, as they typically belong to more disadvantaged groups, many previously lived in old, poorer quality homes, and have limited choice as to where they live: Some customers are very quick to report defects, but some are quite happy to live with them … it tends to depend on where they've come from. If they've come from a really leaky, badly built, turn-of-the-century home, going into any form of a new build is going to be so much better than where they were.
[ … ] And also a lot of affordable housing customers don't have a choice -they don't have the same level of choice that open market customers do. (Planning and Technical Director, HA) It is understandable that the customers of public housing typically do not feel empowered to give feedback about design, functionality of a house, or desired changes, thus preventing housing associations from adopting an effective customer-driven approach. While in other industries relying on the experience of users, competition and choice enables customer research and subsequent design changes for companies to win the market share of customers, in the housebuilding sector, and especially in the social housing sector, even where there is an intention to move to customer-centred production, customers can be disengaged and fail to provide constructive opinions because this is not a sector with competition and customer choice.
Despite all these limitations to expanding customer research activities, interviewed housing associations still confirmed their interest in working with customer feedback and improving their residential experience over the long-term. As social housing providers, housing associations are concerned with the long-term performance of homes and want to ensure tenants' lasting satisfaction with their homes. They refer to them as residents, or tenants, and are motivated to work closely with them to meet their needs.
At the end of the day, one of the values of us being a housing association rather than a developer is that we do see ourselves as long-term custodians of our sites. We are an owner-operator model. We aren't looking for a return based on the initial development, we're looking for that long-term satisfaction. And that comes down to our approach to CapEx and OpEx as well … . when we make decisions based around development, we are making them for the long term. (Head of Design and Innovation, HA) As this section showed, most housing associations perform POE which typically takes the form of twostep customer surveys. However, the interviews found that collected information from residents confines itself to basic customer satisfaction data that is largely needed as a formal instrument to meet the business's KPIs, and the collected feedback has limited quality and detail. This is seen to be because of a lack of resources to collect and analyze data, issues with engaging social tenants, and uncertainty about the benefits that more customer research might bring. Having outlined the existing customer feedback currently collected by housing associations, the next section will examine the feedback loop-the second stage of POE (Hay et al. 2018)-and whether the collected customer data from previous projects is used to inform future design and development of homes.

Gaps in the feedback loop across the supply chain
All participants interviewed in this study recognized the relevance and importance of POE to their organization and its wider value for the industry and the built environment. However, many of them also believed that not enough is being done in this regard, particularly when asked about how (and if) information collected from customers is integrated into the next construction cycle. Many research participants described having a weak feedback loop to transmit residents' opinions to the design and development teams and said that it is often done informally rather than through a developed system of feedback integrated into the business across the supply chain to inform future designs and development. As one interview explained: … there's no formalised route for that feedback at the moment, and it probably relies more on personal relationships rather than actually having a process or a procedure to follow. (Planning and Technical Director, HA).
As demonstrated in the previous section, customer feedback is primarily collected to measure satisfaction but, as part of effective POE, it also needs to be used to improve the design and construction quality of the product. However, the study found that for most housing associations, customer feedback is not integrated into the design of future homes in the construction iterations, rather it is an exception to have an established feedback loop from customers. A representative of one housing association that does have a feedback system in place noted that their feedback loop leads directly from customer-facing departments to the development team: We have a centralised change request log for our specifications. Anybody in the company who's hearing something, be it a customer service representative on the phone, be it an asset manager going out and doing some survey -they can put something on there. Then we review that as a development department and say, yes, we've made that change. Or if we don't make that change, we always go back and say why we haven't made that change. … but the reality is, we're not seeing a huge amount coming through that change log, it's typically coming from a repairs and maintenance side of things, rather than a design perspective. (Director of Development, HA) Housing associations face several barriers to adopting a lessons-learned approach and informing future design and development decisions. Several explanations were given as to why customer feedback generally is not integrated into the design of future homes.
A lack of coordination between the customer side of the business and the development and innovation divisions within is one such barrier, and examples from several housing associations demonstrated that different divisions within a housebuilding organization, especially a large one, function in a detached manner with a minimal exchange of information between them. Reports are only provided vertically to the managing team, making it difficult to integrate feedback into the design process. Better coordination of roles and inputs from different teams is needed, with customer research driven by innovation and design teams with the support of customer engagement teams, rather than by the customer engagement teams alone, as this would enable better integration of the customer feedback into design and development. One of the interviewed participants is already testing this approach in their organization: For using something like MMC … the innovation guys are pulling together a survey which is now going to go out to our customers. It's not the development team doing it and saying what we think is great to do and here's a survey that we've tweaked to make it look good … By doing this through our innovation team, I think it will really help us feed [customer experience] back in. (Director of Development and Growth, HA).
The difference in procurement and construction of homes built using MMC represents another barrier that disconnects customers from the design and development of future homes, as it extends to include MMC manufacturers. The integration of customer feedback becomes more complex and the distance between the end-user (resident) and the manufacturer who defines the quality and designs of MMC-built home becomes significantly longer than in the traditional supply chain, with more actors involved and fewer mechanisms for feeding information into the supply chain. Interviews showed that housing associations have limited control over the design and quality of homes built through MMC, and can only influence their MMC contractors through Employer' The traditional housebuilding approach lends itself to making changes to homes during the construction process, the nature of the MMC production cycle requires greater input for change, and designs are fixed much earlier in the construction cycle. More "buyers" need to request a change to generate a realistic pipeline to encourage the manufacturer to make such a change. The problem of scale has appeared in many interviews when discussing barriers to design changes. As one interviewee asserted, it is a matter of scale and working with multiple manufacturers prevents them from influencing the design of MMC-build homes. Without being able to create a substantial pipeline of MMC products for a manufacturer, housing associations are not in a position to request changes to the end product. The interviewer continued: Each manufacturer comes with their own manufacturing constraints, and therefore their own design outputs differ.
[ … ] If we really want to be a scalable and growth-approached Housing Association, we need to look at efficiencies in design. [ … ] the MMC market at the moment is almost against that, whereas the traditional market is where we can design what we want. (Head of Design and  Innovation, HA) As a consequence, the MMC supply chain and procurement route, particularly of high-category MMC (e.g. volumetric methods), and the various constraints on this still nascent market create limited product choice and control, in contrast to traditional housebuilding. Consequently, housing associations have even fewer opportunities to make efforts to establish effective POE and integrate end-user feedback across the supply chain. However, tailoring the design and quality of homes and proofing technological solutions at the beginning of the MMC journey could be particularly beneficial as the period of early adoption of MMC is precisely the time when work around customer experience is most needed, as it could help to shape the processes and designs as they emerge.
Nevertheless, as highlighted above, to request design and quality changes from the MMC manufacturers, procurement needs to be organized at a scale at which most housing associations with a limited pipeline fail to achieve. As a possible solution, aggregating demand in the MMC market across several housing associations could play this role. As explained by one interviewer, and mirrored by many others, by cooperating, housing associations could create the necessary pipeline for a manufacturer and, as a result, they would have a greater say in the product design and quality: The scale is a big thing. We are a relatively small fish; our program is around 200 homes a year. So, if we were coming in and saying, you know, we want you to change your standard field to suit us, that's just not going to work, or I'm going to pay a significant premium for it. So being part of something collective, where we can collectively say -actually, this [change in design] is important to many of us, and that means 1500 homes of your pipeline are going to require the same change. That puts things in a different perspective. But I think that is one of the constraints of MMC: if people [housing associations] are trying to do it on their own, they're just going to be frustrated and see the costs go up. (Director of Development, HA) Interviews conducted with representatives from the product side of the MMC-based supply chain (i.e. manufacturers supplying high-category MMC) confirmed a further gap in the feedback loop. A lack of direct access and interaction with the end-users of their products (residents) means that MMC manufacturers are largely unable to inform their design and production processes with user experience research. With social housing providers and private developers as their customers, feedback for designs and technology inside the manufacturing organization has to rely on performance indicators of the product rather than feedback from endusers. As one MMC supplier explained, the achieved comfort for occupants is evaluated mainly through post-occupancy performance measurements of the building itself (Strategic Partnerships Director, MMC), and is conducted on a limited number of case study buildings. Resident feedback rarely gets transferred from housing associations to manufacturers due to a lack of resources, interest, or appropriate level of detail. To overcome this hurdle, one of the interviewed MMC manufacturers had begun to collaborate with housing associations to collect data on user experience: With more recent projects, we're working with the housing associations to work to understand the occupants' feelings from living in one of our off-site homes, that's work in progress. Some of that, obviously, is in the hands of the housing association to approve that post-occupancy contact, and also with the residents for consent. It's something that we always like to do, we encourage that conversation with our customers, but ultimately, it's our customers' customer who says yes or no. (Strategic Partnerships Director, MMC) As explained by the interviewed manufacturer, such schemes are aimed at evaluating residents' comfort and measuring performance but are narrowed down to a few case studies where, in these exemplar projects, the manufacturer monitors user experience for several years, continuously receiving resident feedback. This level of post-occupancy contact was made possible because the manufacturer took responsibility to partially fund construction, either through supplying materials to the project or providing their systems and services to the project supply chain team. However, this is an example of a pilot scheme rather than common industry practice.
In the absence of specified mechanisms for transferring resident experience information from housing associations to MMC manufacturers, information sharing needs to be established through closer working relationships between housing associations and manufacturers. For an effective two-stage POE which could enable learning from previous projects and improving future processes and practices, the feedback loop from residents to the design and development now also needs to consider a manufacturer: Housing associations have been doing this a long time, they've already got this engagement loop. [ … ] The difference now is that this will have to include the manufacturer. … The role of the designers is changing anyway, so the manufacturer is going to have a lot more to say. That design loop, that's going to be from resident to manufacturer. So that whole governance around how we continuously improve the product development is something that is now changing. (Group Director, MMC) As the above findings demonstrate, POE is not used in social housing construction by housing associations and MMC manufacturers in the same way as it is in other industries which use customer feedback to improve design and production, and significant gaps exist in the feedback loop between residents and design and development teams. The question arises as to whether UK housebuilding needs to enable an agile, iterative approach to working with customer feedback and access the benefits it could bring, particularly for MMC-based housebuilding in the social housing sector. The findings show that, although the nature of the MMC housebuilding supply chain makes it particularly challenging to carry out effective POE, it is also the sector that could benefit most from it. Setting up an insightful customer feedback loop for homes built using MMC requires more coordination and collaboration across the UK housebuilding supply chain to transmit information from the end-user to the design and development teams of housing associations, and to MMC manufacturers, and to gain a better understanding of the lessons to be learnt along the way.

Discussion: structural factors as barriers to effective POE
Given that many other industries actively use user experience research in agile production and inform their design processes with user feedback (Gothelf and Seiden 2016), this paper asks if the housebuilding industry in the social housing sector could benefit from adapting such an approach. Indeed, if housebuilding in the UK is on a trajectory towards manufacturing and digital transformation through innovative housebuilding and offsite manufacture, modernizing the processes of engaging with end users could enable the industry, and the social housing provision, in particular, to reach even quicker construction times and higher fabrication quality.
As this study's findings showed, the typology of processes of consumer satisfaction evaluation that occur in the social housebuilding sector unfolds in two main categories which correspond to distinct approaches to the use of collected end-user data: (1) standard customer satisfaction surveys that routinely capture whether residents are satisfied with the house and what defects they have found within a fixed occupancy period; and (2) targeted engagement with consumers, with a strong focus on the connected feedback loops to the design and development divisions of the supply chain, which aims to improve quality and housing design and, consequently, to contribute to advancements in the industry and the future of housebuilding. This study of POE in housebuilding in the social housing sector found that, in practice, the first, quite limited type is presently prevalent, and revolves around customer satisfaction. It appears that such a process reflects the existing priorities of the industry, where the two major targets are to deliver more homes more quickly and to minimize the cost of re-working and maintenance. Since customer surveys primarily aim to measure satisfaction, the level of feedback detail is sufficient to evaluate satisfaction rates and report defects but is insufficient to inform design decisions. However, if the purposes of POE included learning from previous projects, customer research in the sector would shift to the second type (with different questions, levels of detail, and levels of resident interaction) and could generate more insights for future developments, particularly in those construction models involving MMC. Indeed, aspirations expressed in the interviews, as well as a successful example of an arrangement of POE collected with the shared involvement of a manufacturer and housing association, illustrate the need for a transition towards the second type of consumer engagement and evaluation. In an agile product development setting with a user-centred model, work with customer feedback is arranged differently. Resources are allocated to conduct research around user experience and in addition to customer satisfaction surveys, they adopt a broad variety of UX methods, including prototype feedback and testing, usability testing, stakeholder interviews and workshops, persona building, expert evaluations, journey mapping, customer visits, user task analyses, user stories, card sorting, and others, depending on the task (Rohrer 2014). Learning from user experience is then looped back into the design and development processes. As a result, timely information collected from users is used to inform the next production cycle and the product evolves to be slightly different each time, with improved features. Competition in such demand-driven industries thus becomes a guarantor of product quality and continuous improvement.
If the UK social housebuilding sector was to embark on a journey to modernize its work with customer feedback in line with other digitally transforming industries, it could derive multiple benefits including tackling issues around build quality and reducing defects and maintenance costs. Enforcing longer-term monitoring of building performance and housing quality will contribute to "the golden thread of information", the capture of which has become particularly critical for the industry since the Grenfell Tower disaster (Burgess et al. 2020). It will ensure customer feedback becomes part of asset information and will further complement the transformation agenda, which has to date been primarily supply-chain focussed, rather than centred on the end-users of built assets. Furthermore, the feedback could provide valuable insights into the next generation of new homes and how they could possibly evolve in their design. Finally, data collected on customer experience could contribute to addressing the negative perception of pre-fabricated homes, particularly among lenders, insurers, and other industry actors (Laing et al. 2001). This could in turn facilitate the uptake of MMC while better meeting customers' needs. As such, systematic learning from previous projects can contribute to the improvement of building performance and quality of housing, creating a built environment that will better fit the needs of end-users, society, and the environment (Hay et al. 2018). Effective use of resident feedback plays a central role in this.
However, as this study found, effective POE faces several barriers to implementation, many of which are pre-determined by the wider structural factors at play in the construction industry and the nature of the MMC supply chain. Structural factors of the supplydriven industry that is housebuilding lead to a focus on short-term gains, such as preferring to address KPIs around satisfaction rates over the long-lasting impact on residential experience through improved housing design and quality. They also lead to a paucity of data collected from end customers, a lack of resources and skills to learn from customer experience, a lack of trust and collaboration in collecting and sharing knowledge on POE, and issues around embedding post-occupancy evaluation in the design and the procurement processes. These structural factors are further reinforced by the absence of a culture of evaluation of the long-term performance of a property after it has been built and while it is occupied.
Furthermore, acknowledging the benefits of manufacturing approaches in construction, it is worth noting that housebuilding differs from manufacturing, not least because it is supply-driven. Demand-driven industries, such as, for example, car production, see competition around cars and their brands, motivating the industry to change; such processes do not work with homes which are sold primarily based on the location and then on the house type and layoutscustomers rarely choose a home because it is supplied by a particular housebuilder or manufacturer. Neither does competitive logic work as a guarantor of better quality in the social housing sector, where tenants have even less choice than private buyers. Housing associations will make their choices of contractors and MMC manufacturers (and associated quality) based on other considerations, typically related to cost. In essence, while the purpose of effective POE is the improvement and better quality of housing, in reality, the housing market in the UK is not conditioned by this factor. Given the shortage of housing stock, high demand for housing, and high prices of houses, there is little motivation for housebuilders to build better homes, only to build more homes. Reinforcing this trajectory, the government has committed to investing £11.5 billion through the Affordable Homes Programme to deliver up to 180,000 new homes by 2028-2029 (HM Treasury 2021). Even though there has been a recently declared ambition to have higher housing quality (Building Better, Building Beautiful Commission 2020, MHCLG 2020a) and to encourage communities to have a greater say in housing design (MHCLG 2020b), this remains a challenge to implement given the barriers in the industry and the context of the housing crisis currently faced by the UK.
As this study has shown, the nature of the MMC housebuilding supply chain adds complexity to customer-centred housebuilding in the social housing sector. To commit to and invest in the design and improvement of their MMC products, manufacturers would require a substantial pipeline of projects to support manufacturing at scale as well as guaranteed access to residents' feedback. Since most social housing providers, especially smaller housing associations, cannot generate this level of demand independently, improvements can only happen if there is coordination with other housebuilders in the sector. Other fundamental factors faced by the UK construction industry and its MMC sector prevent effective POE in MMC-delivered homes, including the slow transition from traditional housebuilding to the wider use of MMC, and fairly recent starts on the MMC journey for both social housing providers and manufacturers of the MMC products.
Technology-related responses are among the solutions for enabling effective POE currently being explored by interviewed manufacturers and housing associations: beyond customer surveys, certain resident data and building performance data can be collected using smart technologies and sensors that allow remote analysis and monitoring. Employing smart home technologies, such as smart metres, sensors, VR, and resident apps, housebuilders and technology providers can provide real-time, accurate feedback from properties that are built with MMC (e.g. Hoyer et al. 2020). Given the current lack of mechanisms for MMC manufacturers to collect end-customer feedback, such technology could be worth considering. However, as interviewees in this study asserted, most of these systems are still in testing mode across case studies and pilot sites, and the social housing sector continues to explore the opportunities that these technologies may have for POE and the data it can bring to the business to inform design decisions. Nevertheless, even when such data input is in operation, the need for qualitative feedback to explore the lived experience of residents and actual uses of housing beyond technical indicators remains vital, particularly for improving technology and housing quality (see Preiser 2001).

Conclusion
In the context of academics (Eggen et al. 2016, Hay 2018, Hoyer 2020, industrial and professional institutions (RIBA 2016), and government (Building Better, Building Beautiful Commission 2020, MHCLG 2020a) alike calling to put customer-centric housing at the core of housing delivery, this paper has explored how post-occupancy evaluation is organized in the supply chain of social housing construction with traditional and MMC approaches. The qualitative evidence has revealed several common perspectives, experiences, and issues relating to POE in social housebuilding in practice. Despite the call for housing delivery to be more customer-focussed, the study found that there are significant gaps in the feedback loop across the supply chain of social housing provision and several barriers to change. As a consequence, residents' experiences and expectations rarely contribute to actual changes in housing design and construction. Several problematic issues emerge in terms of effective implementation, mainly around the structural factors found in the construction industry, such as a focus on customer satisfaction data rather than POE feeding into the design and quality improvements. They include the limiting nature of procurement contracts, a lack of trust and collaboration in sharing accumulated knowledge, an absence of processes and mechanisms to feed information from end customers to other divisions of the company and the broader supply chain, longer supply chains for MMC-based home delivery as more actors are involved, as well as short-termism of housebuilding that limits time and resources for POE activities.
For an effective feedback loop that helps to improve housing quality based on end-customer experience, the POE data collected needs to extend beyond the customer surveys typically used to determine customer satisfaction and identify construction defects, to systematic, qualitative feedback on lived experience and quality issues developed in conjunction with design, innovation and development teams. Such commitment requires significant resources and skills that social housing providers typically do not have. To enable the learning loop of POE, an early collaboration between end-users, designers, innovation and development teams, and, more importantly, MMC manufacturers in the building procurement process, would be needed. As such, enabling a two-stage POE (Hay et al. 2018) that incorporates learning from previous projects, in terms of technology advancement and improvements in quality, could make it possible to detect changing housing needs and address the housing crisis, leading to the building of customer-centric social housing.
Although this study centred on social housing providers, volume housebuilders' attitudes to post-occupancy evaluation and customer research require further exploration. Even if housing associations, having a greater interest in improving residential experience among housebuilders, pioneer the transition to customer-centred housing design and construction, it is volume housebuilders who control most of the new supply in the UK housing market. Further studies to investigate POE in this sector of the housebuilding industry are needed, particularly in relation to the increasing use of MMC technologies. The paper calls for the housebuilding industry to embrace a consistent customer experience research conducted and analyzed both systematically and collaboratively. Note 1. The expression "Employer's Requirements" (ERs) refers to the document(s) produced by the client to set out its requirements in relation to the design and construction of the project (including performance specifications, drawings, initial designs, etc.).

Disclosure statement
No potential conflict of interest was reported by the author(s).

Funding
evaluation.