The housing crisis After the crisis of 2008, it became obvious that the mainstream mechanisms for the provision of housing were failing to provide secure and affordable housing for many households, especially in the countries of the European south such as Spain. It is in this context that alternative forms emerged through social initiatives. La Borda is understood as an alternative form of housing provision and a tenancy form in the historical and geographical context of Catalonia. It follows mechanisms for the provision of housing that differ from predominant approaches, which have traditionally been the free market, with a for-profit and speculative role, and a very low percentage of public provision (Allen, 2006). It also constitutes a different tenure model, based on collective instead of private ownership, which is the prevailing form in southern Europe. As such, it encompasses the notions of community engagement, self-management, co-production and democratic decision-making at the core of the project. Alternative forms of housing In the context of Catalonia, housing cooperatives go back to the 1960s when they were promoted by the labour movement or by religious entities. During this period, housing cooperatives were mainly focused on promoting housing development, whether as private housing developers for their members or by facilitating the development of government-protected housing. In most cases, these cooperatives were dissolved once the promotion period ended, and the homes were sold. Some of these still exist today, such as the “Cooperativa Obrera de Viviendas” in El Prat de Llobregat. However, this model of cooperativism is significantly different from the model of “grant of use”, as it was used mostly as an organizational form, with limited or non-existent involvement of the cooperative members. It was only after the 2008 crisis, that new initiatives have arisen, that are linked to the grant-of-use model, such as co-housing or “masoveria urbana”.  The cooperative model of grant-of-use means that all residents are members of the cooperative, which owns the building. As members, they are the ones to make decisions about how it operates, including organisational, communitarian, legislative, and economic issues as well as issues concerning the building and its use. The fact that the members are not owners offers protection and provides for non-speculative development, while actions such as sub-letting or transfer of use are not possible. In the case that someone decides to leave, the flat returns to the cooperative which then decides on the new resident. This is a model that promotes long-term affordability as it prevents housing from being privatized using a condominium scheme. The grant -of -use model has a strong element of community participation, which is not always found in the other two models. International experiences were used as reference points, such as the Andel model from Denmark and the FUCVAM from Uruguay, according to the group (La Borda, 2020). However, Parés et al. (2021) believe that it is closer to the Almen model from Scandinavia, which implies collective ownership and rental, while the Andel is a co-ownership model, where the majority of its apartments have been sold to its user, thus going again back to the free-market stock. In 2015, the city of Barcelona reached an agreement with La Borda and Princesa 49, allowing them to become the first two pilot projects to be constructed on public land with a 75-year leasehold. However, pioneering initiatives like Cal Cases (2004) and La Muralleta (1999) were launched earlier, even though they were located in peri-urban areas. The main difference is that in these cases the land was purchased by the cooperative, as there was no such legal framework at the time. This means that these projects are classified as Officially Protected Housing (Vivienda de Protección Oficial or VPO), and thus all the residents must comply with the criteria to be eligible for social housing, such as having a maximum income and not owning property. Also, since it is characterised as VPO there is a ceiling to the monthly fee to be charged for the use of the housing unit, thus keeping the housing accessible to groups with lower economic power. This makes this scheme a way to provide social housing with the active participation of the community, keeping the property public in the long term. After the agreed period, the plot will return to the municipality, or a new agreement should be signed with the cooperative. The neighbourhood movement In 2011, a group of neighbours occupied one of the abandoned industrial buildings in the old industrial state of Can Batlló in response to an urban renewal project, with the intention of preserving the site's memory (Can Batlló, 2020; Girbés-Peco et al., 2020). The neighbourhood movement known as "Recuperem Can Batlló" sought to explore alternative solutions to the housing crisis of the time. The project started in 2012, after a series of informal meetings with an initial group of 15 people who were already active in the neighbourhood, including members of the architectural cooperative Lacol, members of the labour cooperative La Ciutat Invisible, members of the association Sostre Civic and people from local civic associations. After a long process of public participation, where the potential uses of the site were discussed, they decided to begin a self-managed and self-promotion process to create La Borda. In 2014 they legally formed a residents’ cooperative and after a long process of negotiation with the city council, they obtained a lease for the use of the land for 75 years in exchange for an annual fee. At that time, the group expanded, and it went from 15 members to 45. After another two years of work, construction started in 2017 and the first residents moved in the following year. The participatory process The word “participation” is sometimes used as a buzzword, where it refers to processes of consultation or manipulation of participants to legitimise decisions, leading it to become an empty signifier. However, by identifying the hierarchies that such processes entail, we can identify higher levels of participation, that are based on horizontality, reciprocity, and mutual respect. In such processes, participants not only have equal status in decision-making, but are also able to take control and self-manage the whole process. This was the case with La Borda, a project that followed a democratic participation process, self-development, and self-management. An important element was also the transdisciplinary collaboration between the neighbours, the architects, the support entities and the professionals from the social economy sector who shared similar ideals and values.                    According to Avilla-Royo et al. (2021), greater involvement and agency of dwellers throughout the lifetime of a project is a key characteristic of the cooperative housing movement in Barcelona. In that way, the group collectively discussed, imagined, and developed the housing environment that best covered their needs in typological, material, economic or managerial terms. The group of 45 people was divided into different working committees to discuss the diverse topics that were part of the housing scheme: architecture, cohabitation, economic model, legal policies, communication, and internal management. These committees formed the basis for a decision-making assembly. The committees would adapt to new needs as they arose throughout the process, for example, the “architectural” committee which was responsible for the building development, was converted into a “maintenance and self-building” committee once the building was inhabited. Apart from the specific committees, the general assembly is the place, where all the subgroups present and discuss their work. All adult members have to be part of a committee and meet every two weeks. The members’ involvement in the co-creation and management of the cooperative significantly reduced the costs and helped to create the social cohesion needed for such a project to succeed. The building After a series of workshops and discussions, the cooperative group together with architects and the rest of the team presented their conclusions on the needs of the dwellers and on the distribution of the private and communal spaces. A general strategy was to remove areas and functions from the private apartments and create bigger community spaces that could be enjoyed by everyone. As a result, 280 m2 of the total 2,950 m2 have been allocated for communal spaces, accounting for 10% of the entire built area. These spaces are placed around a central courtyard and include a community kitchen and dining room, a multipurpose room, a laundry room, a co-working space, two guest rooms, shared terraces, a small community garden, storage rooms, and bicycle parking. La Borda comprises 28 dwellings that are available in three different typologies of 40, 50 and 76 m2, catering to the needs of diverse households, including single adults, adult cohabitation, families, and single parents. The modular structure and grid system used in the construction of the dwellings offer the flexibility to modify their size in the future. The construction of La Borda prioritized environmental sustainability and minimized embedded carbon. To achieve this, the foundation was laid as close to the surface as possible, with suspended flooring placed a meter above the ground to aid in insulation. Additionally, the building's structure utilized cross-laminated timber (CLT) from the second to the seventh floors, after the ground floor made of concrete. This choice of material had the advantage of being lightweight and low carbon. CLT was used for both the flooring and the foundation The construction prioritized the optimization of building solutions through the use of fewer materials to achieve the same purpose, while also incorporating recycled and recyclable materials and reusing waste. Furthermore, the cooperative used industrialized elements and applied waste management, separation, and monitoring. According to the members of the cooperative (LaCol, 2020b), an important element for minimizing the construction cost was the substitution of the underground parking, which was mandatory from the local legislation when you exceed a certain number of housing units, with overground parking for bicycles. La Borda was the first development that succeeded not only in being exempt from this legal requirement but also in convincing the municipality of Barcelona to change the legal framework so that new cooperative or social housing developments can obtain an “A” energy ranking without having to construct underground parking. Energy performance goals focused on reducing energy demands through prioritizing passive strategies. This was pursued with the bioclimatic design of the building with the covered courtyard as an element that plays a central role, as it offers cross ventilation during the warm months and acts as a greenhouse during the cold months. Another passive strategy was enhanced insulation which exceeds the proposed regulation level. According to data that the cooperative published, the average energy consumption of electricity, DHW, and heating per square meter of La Borda’s dwellings is 20.25 kWh/m², which is 68% less, compared to a block of similar characteristics in the Mediterranean area, which is 62.61 kWh/m² (LaCol, 2020a). According to interviews with the residents, the building’s performance during the winter months is even better than what was predicted. Most of the apartments do not use the heating system, especially the ones that are facing south. However, the energy demands during the summer months are greater, as the passive cooling system is not very efficient due to the very high temperatures. Therefore, the group is now considering the installation of fans, air-conditioning, or an aerothermal installation that could provide a common solution for the whole building. Finally, the cooperative has recently installed solar panels to generate renewable energy. Social impact and scalability According to Cabré & Andrés (2018), La Borda was created in response to three contextual factors. Firstly, it was a reaction to the housing crisis which was particularly severe in Barcelona. Secondly, the emergence of cooperative movements focusing on affordable housing and social economies at that time drew attention to their importance in housing provision, both among citizens and policy-makers. Finally, the moment coincided with a strong neighbourhood movement around the urban renewal of the industrial site of Can Batlló. La Borda, as a bottom-up, self-initiated project, is not just an affordable housing cooperative but also an example of social innovation with multiple objectives beyond providing housing. The group’s premise of a long-term leasehold was regarded as a novel way to tackle the housing crisis in Barcelona as well as a form of social innovation. The process that followed was innovative as the group had to co-create the project, which included the co-design and self-construction, the negotiation of the cession of land with the municipality, and the development of financial models for the project. Rather than being a niche project, the aim of La Borda is to promote integration with the neighbourhood. The creation of a committee to disseminate news and developments and the open days and lectures exemplify this mission. At the same time, they are actively aiming to scale up the model, offering support and knowledge to other groups. An example of this would be the two new cooperative housing projects set up by people that were on the waiting list for la Borda. Such actions lead to the creation of a strong network, where experiences and knowledge are shared, as well as resources. The interest in alternative forms of access to housing has multiplied in recent years in Catalonia and as it is a relatively new phenomenon it is still in a process of experimentation. There are several support entities in the form of networks for the articulation of initiatives, intermediary organizations, or advisory platforms such as the cooperative Sostre Civic, the foundation La Dinamo, or initiatives such as the cooperative Ateneos, which were recently promoted by the government of Catalonia. These are also aimed at distributing knowledge and fostering a more inclusive and democratic cooperative housing movement. In the end, by fostering the community’s understanding of housing issues, and urban governance, and by seeking sustainable solutions, learning to resolve conflicts, negotiate and self-manage as well as developing mutual support networks and peer learning, these types of projects appear as both outcomes and as drivers of social transformation.

The term 'retrofit' remains a subject of debate, often used interchangeably with 'refurbishment' and 'renovation', lacking a clear distinction. Linguistically, the Oxford English Dictionary (2023) defines 'retrofit' as: "A modification made to a product or structure to incorporate changes and developments introduced since manufacture or construction; the action or fact of modifying a product or structure in this manner. Also figurative. Concerning buildings, in later use, often implying (an instance of) the making of adaptations to improve energy efficiency or to counteract or mitigate the effects of climate change." For buildings, retrofit encompasses substantial physical modifications made to them. These changes can stem from two kinds of activities: mitigating activities aimed at improving energy efficiency and adaptive activities, often referred to as 'adaption', involving interventions such as adjustments, reuse or upgrades to align the building with new requirements or conditions  (Dixon, 2014). The retrofitting process of this old tenement at 107 Niddrie Road involved activities for various purposes. For instance, external activities included preserving the aesthetic appearance and heritage of Glasgow's iconic housing typology. The internal activities included repairing all services, including urgent maintenance for timber elements and structural enhancements for future residents' safety. The retrofitting decisions were also made as a response to the pressing demands of climate change and the future needs of residents. However, these decisions were primarily based on the expertise of the landlord (the housing association), architects, and the Passivhaus enerPHit standard rather than the active involvement of the future occupants (see RE-DWELL blogpost Retrofit and Social Engagement).  In this case study, we will only focus on three primary goals of the retrofitting process: low energy consumption, low carbon emissions, and ensuring the health and wellbeing of future dwellers. Low energy consumption The 107 Niddrie Road is an example of how to tackle fuel poverty among dwellers living in this type of historic housing stock. In Scotland, approximately 30% of families living in traditional tenements (equivalent to 175,000 homes) are considered to be fuel poor. The substandard housing conditions of old tenements make it challenging to maintain indoor warmth. Consequently, a substantial portion of a family's income is allocated to energy bills, exacerbating fuel poverty. The retrofit involved implementing several energy measures aligned with the Passivhaus enerPhit standard to enhance the tenement's energy efficiency. The architects of John Gilbert expect these measures to result in slashing heating costs by up to 90%. Therefore, this retrofit can be considered a deep energy retrofit. Deep energy retrofit provides up to 60 % energy savings by upgrading the building using "a combination or "package" of multiple energy measures that upgrade the physical fabric, heat generation system and lighting of a building" (Page 3, Saffari & Beagon, 2022). The adopted energy measures for this deep energy retrofit included: 1) Retrofitting the fabric:  It involved insulating walls, roof, and ground floor, installing triple-glazed windows, and ensuring airtightness to minimise thermal bridging. The retrofit also guaranteed a continuous airtightness line, including all key junctions at the attic level, windows, and doors. 2) Use of Waste Water Heat Recovery (WWHR) system:  This system heats cold water using heat recovered from shower or bath drain water. This method significantly reduces hot water costs and carbon emissions by approximately 40%. Given that heating water represents the second largest cost of a fuel bill, this system is expected to substantially reduce these costs and carbon emissions. 3) Individual Air Source Heat Pumps (ASHP):  These units were installed in the four flats on the lower floors. In parallel, efficient combi gas boilers were set up in the remaining flats to compare their performance with ASHP during residents' occupancy. Low carbon emissions Various measures, including the installation of ASHP and WWHR systems and the utilisation of natural materials, were implemented in a bid to reduce carbon emissions and combat climate change. The project minimised its environmental impact using fewer new materials than new construction blocks. The UK Collaborative Centre for Housing Evidence is currently evaluating the extent of the carbon reduction achieved through these measures. Ensuring health and wellbeing By adopting the Passivhaus enerPHit standard, the project prioritised occupant comfort, indoor air quality, and energy efficiency. Expected benefits include: 1) Thermal comfort and reduced energy costs: The retrofit project aimed to maintain warmth during winter and coolness in summer, thereby reducing energy costs, improving residents' quality of life, and minimising temperature-related stress amid rising energy expenses and extreme temperature fluctuations. 2) Damp and mould mitigation for indoor air quality:  Condensation and humid air are common issues in Scottish homes, often leading to dampness and mould, adversely affecting residents' health. The project implemented the following techniques to mitigate these risks: Improving ventilation: A high-performance Mechanical Ventilation Heat Recovery (MVHR) system was installed to provide constant fresh air while extracting humidity. Contrary to a common misconception that installing MVHR eliminates the need to open windows, it is possible to do so in moderation, particularly during extreme temperatures, to conserve energy. Ensuring air tightness: Thermal bridges, which leak heat during winter and create cold spots on walls, were eliminated. The retrofit assured continuous airtightness line. Using breathable materials: Lime plaster was used for airtightness and vapour-permeable wood fibre for insulation. These materials mitigate common moisture-related risks in highly airtight buildings. 3) Reduced toxicity of materials for indoor air quality: Efforts were made to minimise indoor air pollution by opting for natural building materials wherever feasible. These materials were chosen to uphold excellent indoor air quality and reduce low-level toxins that could exacerbate health problems, especially for vulnerable individuals. Additionally, chemical treatments on wood were avoided to limit exposure to harmful substances and reduce costs. 4) Altered layout for better functionality and accessibility: Major changes were made to make dwellings more functional for households and guests. Some of the changes contributed to optimising available space, demonstrating the adaptability of the existing property. These adjustments aimed to improve accessibility while complying with current building regulations. A comparison of the before and after floor plan images reveals two main differences. Firstly, the kitchen was relocated closer to the living room area; it was distant and only accessible through the bedroom, making it impractical. Secondly, the bathroom was redesigned to accommodate a spacious shower, and the toilet was moved from the end of a long and narrow corridor. This change ensured accessibility, especially for family members using a wheelchair. 5) Preserve the tenement heritage: The street-facing facade was internally insulated, ensuring the building's historic appearance was preserved. Additionally, triple-glazed windows were carefully chosen to keep the traditional window frame design. Replicating this retrofitting process on a large scale The retrofit project at 107 Niddrie Road represents a noteworthy example of successfully implementing the Passivhaus enerPHit standard for deep retrofitting old tenements. The retrofit incorporated a range of energy efficiency techniques, including enhanced ventilation systems and the use of natural, non-toxic materials. However, replicating these retrofits on a larger scale presents some advantages and challenges. For instance, retrofitting several tenements at once could offer the financial benefit of bulk purchasing advanced energy-efficient technologies, like heat pumps, potentially reducing overall costs. However, the social factor of the dwellers poses a challenge in replicating these projects on a larger scale, mainly when dealing with multiple tenements being retrofitted simultaneously. Minimising disruptions to residents' daily lives during work is imperative to ensure the success of building retrofitting. In inhabited properties, resident cooperation becomes pivotal for project success. Resistance or a lack of understanding among residents can impede the implementation process. Retrofritting an inhabited dwelling disturbs household life. Communicating the benefits of the retrofit project and addressing residents' concerns becomes paramount, which is also time-consuming and financially burdensome for housing associations. Therefore, a critical factor that contributed to the successful process of executing the retrofit in this case was the vacant status of the flats, which might not be the case for other Scottish tenements. Retrofitting tenements on a large scale faces several technical challenges, including the absence of a dependable supply chain for advanced technologies like heat pumps. Some technologies mandated by the Passivhaus standards are relatively new to the UK market. Additionally, the technical expertise required to install and maintain these advanced technologies is still inadequate.

Efforts to target renovation subsidies, particularly in areas with households at risk of energy poverty, have gained prominence across Europe. However, the way in which policymakers and governments design and implement the targeting process varies greatly. Targeting energy poverty is rather difficult because it is a multifaceted issue and you have to identify which households both have limited means and high needs of energy due to their personal circumstances or the energy inefficiency of their home (Dubois, 2012). This case study zooms in on a peculiar example of such targeting: the Dutch Volkshuisvestingsfonds (VHF), in which national government asks municipalities to proof both that their housing stock is of substandard quality and that these dwellings are located in deprived neighbourhoods. This way, the fund tries to combine boosting the energy transition as well as aiming for ‘levelling up’ targets. Background Recognising the pressing need to address issues of liveability and housing quality, the Dutch Ministry of the Interior and Kingdom Relations (BZK) initiated the VHF in 2021 (Ministerie van BZK, 2021). The fund’s creation was influenced by rising concerns about housing conditions in socio-economically disadvantaged regions, where private homeowners and investors are facing significant barriers to maintaining and upgrading properties. A possible rationale is to avoid a downward spiral where the physical quality of a neighbourhood declines, prompting middle-income residents with more resources to leave, which in turn further worsens the overall quality of life in the neighbourhood (Andersen, 2002). Consequently, the primary goals of the VHF include the retrofitting of existing housing stock, demolition and reconstruction where necessary, and the enhancement of public spaces in neighbourhoods that are deemed relatively deprived. The fund aims to support private landlords with insufficient financial capacity and to a lesser extent housing associations. Policy design and delivery The VHF's design emphasises a targeted approach, where municipalities must demonstrate the substandard quality of their housing stock and the socio-economic deprivation of these neighbourhoods. Priority is given to urban renewal areas and regions facing population decline (see Figure 1). Municipalities are then allocated resources based on the severity of these conditions. Specific consultancy groups are appointed to assist municipalities in preparing their bids, ensuring that applications are robust and meet the stringent criteria set by the fund. The bid evaluation process involves a detailed scoring system that considers several factors: the extent of housing quality improvement, the anticipated socio-economic benefits, the energy efficiency gains, and the sustainability of the proposed interventions. Once a municipality's bid is approved, the funds are disbursed to the municipality, which then channels the money to the ultimate beneficiaries (hence, primarily private landlords with limited means). These beneficiaries must use the funds for approved renovation projects, with strict monitoring to ensure compliance and prevent misuse. In its first round in 2021, the fund distributed approximately €412.6 million, financing projects aimed at upgrading around 22,000 homes. As of summer 2024, the fourth round is open, now allocating €114 million. One of the unique aspects of the VHF is its dual focus on energy efficiency and socio-economic uplifting. By linking housing improvements with broader ‘levelling up’ goals, the fund addresses both the physical infrastructure and the social dynamics of neighbourhoods. This way, it could be seen as a preventive measure that addresses the risk of self-reinforcing decline in which a neighbourhood’s physical quality degrades, leading to the exodus of middle-income residents. To do this, the VHF employs a data-driven approach to target and allocate funds. Municipalities are required to provide detailed data on housing conditions and socio-economic indicators. This data is used not only to evaluate the bids but also to monitor the progress and impact of the funded projects, which holds the promise of transparency and accountability, making it easier to measure the success of the interventions and to make necessary adjustments. Finally, the VHF encourages collaboration between the national government, municipalities, private firms, private landlords, and other stakeholders, making it a comprehensive public-private endeavour. Challenges in implementation Despite the innovative design and promising objectives, several critiques have emerged regarding its implementation. The official evaluation commissioned by the ministry noted that one significant concern is the high administrative burden placed on municipalities, which makes the application process complex and resource-intensive (Eringfeld et al., 2022). This complexity can disadvantage smaller municipalities or those with less capacity, exacerbating regional inequalities. Additionally, they claim there is a need for a more permanent flow of financial resources to ensure the sustainability of improvements and to fund new projects continually. The report also highlights challenges in measuring the long-term impact of funded projects, particularly concerning socio-economic benefits and energy efficiency gains, necessitating more robust mechanisms for impact assessment. Another critique centres on stakeholder engagement, with some municipalities struggling to involve private landlords and residents effectively in planning and implementation. Regulatory challenges further complicate efficient project execution, particularly compliance with EU state-aid legislation. Moreover, there is concern that subsidising private landlords with public money may have a regressive impact on income and wealth distribution, as it ultimately provides a housing value premium to private landlords (Fernández et al., 2024).

Strengthening Construction Quality and Knowledge Sharing The City of York's procurement strategy for the Duncombe Square project, as well as other housing sites across the city, focused on two key objectives: ensuring high-quality construction and facilitating knowledge exchange about sustainable building practices. These objectives exemplify the council's commitment to its housing delivery programme. To achieve housing quality, the council engaged a multidisciplinary design team led by the esteemed architect Mikhail Riches, known for his work on Norwich Goldsmith Street and association with the Passivhaus Trust. This team was supported by RICS-accredited project managers, clerks of work, and valuers to uphold stringent standards. The project used two complementary approaches to improve the construction and delivery of large-scale Passivhaus projects in the UK. The first approach involved training to advance sustainable construction skills for existing staff, new hires, and students aged 14 to 19, led by the main contractor, Caddick Construction (Passivhaus Trust, 2022). The second approach is sharing knowledge with a broader audience by organising multiple tours during the different construction phases. These tours were designed for developers, architects, researchers, and housing professionals. They showcased Duncombe Square as an open case study, allowing industry peers to learn from and engage directly with project and site managers, reinforcing the project's role as a model for York’s Housing Delivery Programme. Duncombe Square Housing Design The design principles of the Duncombe Square project aim to integrate functionality and encourage healthy and sustainable lifestyles. The principles embody the essence of Passivhaus design while ensuring aesthetic appeal. It features low-rise, high-density terraced housing to optimise land use and foster a sense of community. The terraces are strategically positioned close together to maximise solar gain during the winter hours of sunlight, ensuring compliance with the rigorous Passivhaus standards while accommodating a maximum number of residences. The design ensures that each home benefits from natural light and heat while aligning with the Passivhaus energy efficiency and ventilation principles. The facade design and colour scheme connect with the local architectural identity of traditional Victorian terraces, with a modern twist that cares for indoor environmental quality. It features high ceilings, thick insulated walls, and a fully airtight construction. The design incorporates traditional materials such as brick, enhanced by modern touches of render and timber shingles that blend harmoniously with the local surroundings. The site plan design reflects a neighbourhood concept that extends beyond the energy-efficient and modern appearance of the houses. Duncombe is designed as a child-friendly neighbourhood, prioritising walking and cycling with dedicated cycle parking for each home. Vehicle parking and circulation are situated along the site's perimeter, ensuring paths are exclusively for pedestrians and play areas. Additionally, shared 'ginnels' provide bike access, enhancing mobility and creating safe play areas for children. This emphasis on pedestrian access enhances community interaction and outdoor activities. The thoughtful landscaping incorporates generous green open spaces at the development's core, complemented by communal growing beds and private planters. These features are intended to be aesthetically pleasing while also encouraging community engagement.   A Construction Adventure For the main contractor, Caddick Construction, this project represents a distinctive adventure - from procurement to construction to Passivhaus standards - that deviates from traditional British construction practices. Recent UK housing developments often employ "Design and Build" contracts, where the contractor assumes primary responsibility for designing and constructing the project. However, the architects led the design process in this case, necessitating frequent collaborative meetings to discuss detailed execution plans. During a site visit to the project site in York in September 2023, the contractor’s site manager explained the challenges of constructing and applying Passivhaus standards on a large scale. Unlike traditional construction, Passivhaus demands meticulous attention to detail to ensure robust airtightness of the building envelope. Moreover, building to these standards involves sending progress images to a Passivhaus certifier, who verifies that each construction step meets the rigorous criteria before approving further progress.   The chosen construction method for this project is off-site timber frame construction combined with brick and roughcast render. Prefabricated timber frames mitigate risks for contractors and expedite the construction process. The homes' superstructure employs timber frame technology, ensuring durability and longevity. A key priority in the construction process is preventing heat loss and moisture infiltration. This involves: Envelope Insulation: Airtightness is crucial for minimising heat loss. Therefore, the façade installation included airtight boards, tapes, membranes, timber frame insulation, and triple-glazed windows. Indoor airtightness is tested at least four times throughout the construction process to guarantee that residents will live in an airtight house. Foundation and Floor Insulation: Three layers of insulation between the floor finishing and foundation prevent heat loss, enhance thermal efficiency, and control moisture penetration, protecting against groundwater leakage.   Households’ Health and Wellbeing Households' health and wellbeing are foundational pillars in the development of the Duncombe Square project. In addition to the robust energy efficiency benefits of Passivhaus standards, this initiative underscores high indoor air quality through Mechanical Ventilation with Heat Recovery (MVHR) units, which improve air quality and help mitigate issues like dampness and mould in airtight houses. To improve outdoor air quality, the design strategically reduces car usage by fostering a pedestrian-friendly environment with expansive green pathways that purify air and encourage outdoor activities. Amenities such as bike sheds with electric charging points and communal "cargo bikes" are also included. Central to the project is a vibrant communal green space that facilitates relaxation, play, and social interactions—vital for mental and physical health. The scheme enhances residents' wellbeing by ensuring proximity to local amenities, promoting a healthier, more active lifestyle without reliance on vehicles. Extensive pedestrian and cycling paths, alongside wheelchair-friendly features, highlight the project's commitment to inclusivity and a healthy living environment. The design harmoniously integrates with local architecture and includes public amenity spaces that prioritise safe, child-friendly areas and places for social gatherings, fostering a strong community spirit.   When compared with the framework for sustainable housing focusing on health and wellbeing developed by Prochorskaite et al., (2016), the Duncombe project excels in incorporating features such as energy efficiency, thermal comfort, indoor air quality, noise prevention, daylight availability, and moisture control. Moreover, it emphasises accessible, quality public green spaces, attractive external views, and facilities encouraging social interaction and environmentally sustainable behaviours. Its compact neighbourhood design, sustainable transportation solutions, proximity to amenities, consideration of environmentally friendly construction materials, and efforts to reduce greenhouse gas emissions perfectly encapsulate the framework's objectives for providing sustainable housing focused on health and wellbeing. Affordability From a housing provider's perspective, the delivery team faced challenges in achieving a net-zero and Passivhaus standard that is affordable and scalable for large housing developments. For instance, construction costs are subject to pricing risks as contractors raise their prices amid market uncertainties, thereby increasing overall project expenses. Integrating Passivhaus principles is believed to have helped control these costs by simplifying building forms and reducing unnecessary complexities. Residents' housing affordability is expected to be positively influenced by three key factors: tenure distribution, adherence to Passivhaus standards, and the development's central location. The tenure distribution includes 20% of units for social rent and 40% for shared ownership, offering affordable options for both renters and prospective homeowners. Passivhaus standards further reduce costs by lowering energy consumption through features like PV panels and energy-efficient air-source heat pumps, earning the development an A rating for energy performance and cutting utility bills for residents. Additionally, the central location decreases mobility-related expenses, with easy access to local amenities reducing the need for car use. Together, these factors help promote a sustainable lifestyle and lower overall living costs for residents.  Sustainability: Environmental, Social, and Economic Lens Environmental sustainability involves two key aspects: (1) reducing resource consumption and (2) minimising emissions during use (Andersen et al., 2020). Duncombe Square's initiatives to reduce resource consumption include: The dwelling's superstructure utilises low-carbon materials, such as FSC (Forest Steward Council) certified timber framing, which ensures it is sourced from sustainable forestry. Using recycled newspaper for insulation to minimise environmental impact. Monitoring the embodied energy of construction materials, including accounting for the energy used in their extraction, production, and transportation. Sourcing 70% of subcontractors and supplies within 30 miles of the site, as per Passivhaus Trust guidelines, to reduce emissions from long-distance transportation. To minimise environmental impact during use, the project incorporates: Air-source heat pumps for heating and solar PV panels on roofs, enabling net-zero carbon energy usage. Water butts for collecting rainwater for gardening purposes. Permeable surfaces, rain gardens, and Sustainable Urban Drainage Systems (SUDS) to reduce surface runoff in public areas. Economic sustainability is at the forefront of providing affordable, energy-efficient dwellings that do not impose long-term financial burdens on residents. The project offers affordable dwellings in terms of housing costs, non-housing costs, and housing quality. It also contributes to the broader economy by promoting sustainable building practices and creating future jobs through on-site training programmes. Caddick Construction prioritises the local sourcing of subcontractors and suppliers within 30 miles of the site, thereby reducing transportation costs and supporting the local economy. Social sustainability is integral to the project, featuring designs that promote community interaction and provide safe, accessible outdoor spaces. The development includes communal green spaces, such as plant-growing areas and a central green space for natural play, enhancing residents' quality of life. Prioritising pedestrian pathways and extensive cycle storage encourages a shift towards sustainable transport options, reducing reliance on cars and promoting healthier, more active lifestyles.

  Community-led housing projects The Can70 project exemplifies the significance of community-led housing initiatives, where residents actively participate in the decision making from initiation and planning to development. By engaging in the initial design and subsequent development stages, residents gain a profound sense of ownership. This involvement ensures that the project aligns with the values and aspirations of the dwellers. The community has established a governance structure to facilitate their participation, emphasizing consensus within the general assembly. This structure is composed of five commissions -community, governance, economy, architecture, and external affairs- which play pivotal roles in ensuring effective project management and community engagement. While residents take the lead, they still require resources, public support, and technical assistance to bring the project to fruition. The cooperative Sostre Civic has guided them in navigating legal, economic, and communication aspects with the public sector. This collaborative effort underscores the importance of synergy between community-driven initiatives and external expertise. Care and mutual support The community has recognized the importance of incorporating care and mutual support into their co-living model. Their goal is to live in an environment where their members actively support one another, creating a safety net that enhances well-being and quality of life. Through organized activities, informal interactions, and shared responsibilities, care will become an integral part of their daily lives. This way of living together contrasts with the institutionalization of senior care in nursing homes, which the members of Can70 aimed to avoid. Maintaining their autonomy while being part of a supportive community was a key motivation for the group. A significant aid in researching the connection between housing and care was the two-year effort to write the "Guide of Care in the Coliving of Elderly People." This project was supported by a grant from the Department of Elderly People of the City Council of Barcelona. Initially awarded for one year, the grant was extended for a second year. The group systematically explored what care means to them, and the resulting guide is available for everyone to consult, aiding new groups in similar endeavors. Innovative living forms The project integrates innovative architectural design and spatial distributions. The building features a spectrum of spaces ranging from private to public, enabling residents to utilize them in diverse ways. The publicly accessible areas of the building connect it with the neighbourhood, communal spaces foster socialization among the building’s inhabitants, and semi-private spaces act as thresholds between public and private realms, giving rise to a smaller nuclei of cohabitation within the building. Since residents plan to live there for the rest of their lives, an important decision was to have single-person units, even for couples. In that way, the person who loses a partner will not have to change their living unit and can continue living in their familiar environment. The group incorporated many apartments using the cluster typology, 4-5 private units of 30m² —each with a bathroom, bedroom, and small kitchenette— around a shared space of 50m², equipped with a kitchen, dining area, and small living room. This layout facilitates easier mutual care within smaller groups. It was also decided to include some conventional 45m² apartments for those who prefer less shared living arrangements. Finally, the building includes various communal spaces, including a shared kitchen, a reading area, and a day centre. An important feature is a semi-open communal space on every floor next to the vertical communication areas, enabling residents to socialise on each floor and seamlessly integrating communal spaces throughout the building. Relationship to urban environment The objective of the community has been to create a housing project integrated within the neighbourhood. Since the project is being developed on public land, one requirement of the city council for granting the land to the cooperative was to include public spaces on the ground floor. The group embraced this condition, having already envisioned areas open to the community. The building's ground floor will feature spaces accessible to the public during specific hours, including facilities for physiotherapy, potentially hydrotherapy, a day centre, and care services. Additionally, there will be activities open to the neighbourhood, such as discussions and presentations on well-being and elderly care, as well as storytelling sessions for young children. This approach ensures that the project's social impact extends beyond its residents, fostering social bonds and connections within the local community. Environmental and social sustainability From the outset, the group prioritized the project's environmental sustainability, which was evident in the decisions concerning the building's bioclimatic design, construction system, energy efficiency, and shared resources among residents. In collaboration with the architects, Peris+Toral, they chose compressed earth blocks for construction, a material that maintains a stable internal temperature and minimises the need for mechanical cooling or heating systems, thus reducing the environmental footprint of the building. Initially, the group considered using a wooden construction system (CLT), inspired by projects like La Borda in Barcelona. However, rising material cost of wood necessitated a plan change showcasing the group’s flexibility and commitment to find a sustainable solution. Sustainability is also reflected in the project’s various shared resources. The community plans to share daily meals in the communal dining area on the ground floor. Additionally, the clusters of the housing units will include a shared kitchen for four to five residents living together, allowing them to share groceries and take turns cooking. Furthermore, residents will also share laundry facilities. These decisions collectively enhance the project's overall sustainability and foster a strong sense of community. Societal impact Can70 will achieve a significant societal impact by envisioning and materializing an alternative model for ageing in the community. The group has created a co-housing project based on autonomy and mutual support among residents, demonstrating the crucial role of community participation in all project phases. This innovative approach highlights the benefits of co-living arrangements for the elderly, where shared responsibilities and collective decision-making contribute to a higher quality of life and increased well-being. In addition to providing a successful model for communal living, the project has also contributed to transform the current legal framework. Can70 has been the first senior project to be incorporated under the grant-of-use scheme, setting a precedent for future initiatives of older communities. This legal recognition paves the way for developing similar projects, allowing the scaling up of senior co-housing.

In Europe, the push for energy-efficient housing has led to widespread use of financial incentives such as grants, loans, and tax rebates to encourage homeowners to undertake retrofits. These measures aim to reduce energy consumption and improve the environmental performance of residential buildings. Governments across the continent have adopted various programs to support these efforts, offering significant financial aid to make energy-saving improvements more accessible to homeowners. In addition to subsidies, some countries implement energy taxes to further promote efficiency and fund sustainability initiatives. At the European Union level, comprehensive strategies are being developed to enhance the energy efficiency of buildings, including proposals for new regulatory frameworks and financial incentives. This multi-faceted approach reflects a growing recognition of the importance of sustainable housing in achieving broader environmental and economic goals. Subsidisation of housing retrofit, through grants and loans, as well as tax rebates are commonly used across Europe to incentivise the energy-efficient retrofit of the housing stock (Castellazzi et al., 2019). Following this trend, the Dutch government has put in place a series of grants and subsidised loans to incentivise retrofit. First, the “Subsidie Energiebesparing Eigen Huis” is a grant programme covering up to 50% of retrofit costs when at least two energy-saving measures improving EPC levels have been implemented. Dutch homeowners can also apply for the Investment Grant for Sustainable Energy Savings (ISDE) in the case of single measures such as solar boilers or heat pumps (Ministry of Economic Affairs and Climate Policy, 2019). Since 2022, 0% interest loans are also available to low-income households from the National Heat Fund. On the stick side of retrofit incentivation, the Netherlands implements a regressive form of carbon taxation on individual households (Maier & Ricci, 2024). Research by the Dutch National Bank has also alluded to the strong impact of energy taxation on lower incomes and the inelasticity of energy consumption. Havlinova et al. (2022) have found that the introduction of stronger forms of energy taxation in heated energy markets can impinge on lower incomes resulting in regressive distributional impacts. At the EU level, the Renovation Wave is actively promoting this approach to housing retrofit through its proposal to include buildings in the Emissions Trading Scheme (ETS) together with the implementation of retrofit subsidies(2003/87/EC). As a result, while owner-occupied housing is undertaxed, the tax burden on energy consumption at the household level is poised to increase. Retrofit subsidies usually come to join fiscal systems favouring owner occupation. These forms of direct subsidisation of housing retrofit coalesce with increases in the fiscal burden on energy consumption. According to Haffner & Heylen (2011), the housing taxation structure favours owner-occupation with a mortgage through large deductions in income tax. In the Netherlands, imputed rent, the main form of housing taxation is calculated on the basis of a notional rent value and then added onto box 1 which comprises labour income. All other income from investments is taxed under box 3 at a different rate. Haffner & Heylen (2011) have analysed the lack of tax neutrality in this system and propose to include the taxation of housing assets under box 3 as a tax-neutral benchmark. In the context of housing retrofit, the favourable fiscal treatment of homeownership comes to join generous subsidies for owner-occupied housing retrofit with no maximum income threshold offered by the Dutch government. A green tax  is a viable alternative to incentivise retrofit in a more progressive manner. The Dutch approach to incentivising housing retrofits exemplifies a broader European commitment to enhancing energy efficiency through a combination of financial incentives and regulatory measures. While generous subsidies and tax incentives significantly benefit homeowners, particularly those with mortgages, the regressive nature of energy taxation presents challenges for lower-income households. Research indicates that increased energy taxation disproportionately impacts these households, underscoring the need for more progressive solutions. The EU’s Retrofit Wave, along with the proposed inclusion of buildings in the ETS, reflects an ongoing effort to balance these measures. In the context of housing retrofits, a shift towards green taxes could provide a more equitable framework, ensuring that the financial burden and benefits of energy-efficient improvements are more evenly distributed across different income groups.   (This text is an excerpt from : Fernández, A., Haffner, M. & Elsinga, M. Subsidies or green taxes? Evaluating the distributional effects of housing renovation policies among Dutch households. J Hous and the Built Environ (2024). https://doi.org/10.1007/s10901-024-10118-5 )