Sustainable developments in social housing, a secondment at South Yorkshire Housing Association.

a) Design philosophy According to the Housing Design Awards, the design of the North Wingfield project took a contemporary design approach, combining the features of local vernacular architecture - as adopted from local farms - with the developer's vision and requirements for flexible, sustainable and innovative housing (HDA, 2021). The architectural office DK -Architects explains that this fusion is represented by massing the morphology of the project, traditional architectural elements (e.g. Dreadnought brick (roof), Janinhoff brick (walls)) with modern elements such as large glazing and aluminium cladding. This combination of materials not only provides an aesthetically pleasing appearance, but also helps to capture heat, ultimately reducing heating energy consumption for at least seven months of the year (DK-A, 2021). In addition, several innovative features have been adapted, including the well-planned use of space and the clear conceptual plans that extends beyond the interior spaces to the shared courtyard, which serves as a social gathering place for the tenants. The inspiration for the courtyard was derived from the local identity, the farmstead and the crew yard (HDA, 2021). At the same time, the use of a see-through fence, which extends the sightline into the rural surroundings, provides a calming splash of green colour in each residential unit. The semi-raised upper massing extends the courtyard and provides a semi-enclosed space that enhances the feeling of safety and security (DK-A, 2021). Meanwhile, the buildings in the front row clearly stand out from the surrounding buildings through the use of colours and materials and also serve as an entrance gate to the project (DK-A, 2021; HDA, 2021). Each dwelling has its own mini agricultural space, which has proven valuable for the well-being of the residents. b) Construction process The skeleton of the building utilises an off-site timber frame method of construction, adopting a semi-modular design principle (Davies & Jokiniemi, 2008). This construction method provides a structure with a superior thermal envelope that requires minimal maintenance and is a 'fit-and-forget' solution for the lifetime of the building. In addition, both labour and material costs were significantly reduced due to less reliance on craftsmanship and multiple suppliers. This is in line with the UK government plans to revamp construction regulations to encourage bold, creative and sustainable construction methods (Davies & Jokiniemi, 2008; Sterjova, 2017). The construction process started with ground treatment, followed by the casting of the foundations on site. Meanwhile, the timber frames were manufactured off-site at the supplier's factory, which helped to reduce construction work and thus carbon emissions. The frames were then transported to the site for fixing and external treatment, and all the construction work ran in parallel (Wheatley, 2020). The overall process can be seen in Figure 1. c) Sustainability integration At the sustainability level, the project worked on several areas to maximise the adaptation of sustainability features and minimise the impact on the natural environment (HDA, 2021). Creating sustainable buildings Through sustainable design and layout (e.g. orientation, maximising daylight, optimising solar gain). Creating high quality outdoor environments (e.g. public and private open spaces that provide shade and shelter and consider flood retention and multi-functional green spaces to protect wildlife). Use of sustainable water management techniques (e.g. use of sustainable drainage systems and consideration of surface water run-off). Use of sustainable waste management facilities for private and communal use (through the appropriate provision of waste and recycling bins). Focus on reducing the use of non-renewable energy. Reduction of carbon emissions The project has been designed in accordance with the highest level of building regulations and sustainability standards, in line with the Government's 10-year timetable for all new homes to be carbon neutral by 2016. Water recycling techniques (such as grey water and rainwater harvesting). Sustainable Transport (reducing reliance on the private car, incorporating practical and accessible sustainable transport patterns). d) Energy performance One of the tools to assess building energy efficiency in the  UK is the Energy Performance Certificate (EPC), which is defined by the Department for Levelling Up, Housing and Communities as: A rating scheme that summarises the energy efficiency of buildings; it includes a certificate that gives a property an energy efficiency rating from A (most efficient) to G (least efficient) and is valid for 10 years (DLUHC, 2014). The EPC is produced using the Standard Assessment Procedure (SAP), which is defined by the Department for Business, Energy & Industrial Strategy as follows: The method used to assess and compare the energy and environmental performance of properties in the UK [...] it uses detailed information about the property's construction to calculate energy performance (DBEIS, 2013). The North Wingfield project has successfully achieved a (B) rating - equivalent to 84 out of a maximum possible 100 points with a high potential for an (A) rating equivalent to 95 points (DLUHC, 2021). This score is the result of The use of high-performance materials with very good thermal transmittance properties (walls: 0.20 W/m²K, roof: 0.11 W/m²K, floor: 0.09 W/m²K). Well-designed ventilation system that achieves a good air tightness indicator (air permeability 4.9 m³/h.m²). Low consumption of primary energy of 94 kWh/m2. Another indicator is the Environmental Impact Score (EIS), which shows the impact of a building on the environment through the estimated carbon dioxide (CO2) emissions calculated at the time of the EPC assessment (DLUHC, 2014). The higher the score, the lower the building's impact on the environment: like EPC labels, the environmental impact score is graded from A to G (DBEIS, 2014). The project generates 1.4 tonnes of CO2 annually. This is less than a quarter of the 6 tonnes emitted by an average household. By improving the EIS rating to A, CO2 production will be reduced to 0.3 tonnes, which will distinguish the project as one of the most environmentally friendly projects (DLUHC, 2021). Figure 2 shows the EPC and EIS breakdowns of the properties.

The review of this case study is structured to address aspects of architectural design, construction approach, and sustainability integration. The analysis draws on a range of data sources, including project design and access statements, sustainability statements, design drawings, planning applications, associated communications and archival records obtained from the planners, public records and the London Borough of Lambeth planning portal.   1. Design statement The project site stretches to approximately 0.86 hectares, 84 residential units at a density of 215 dwellings per hectare are planned to be housed on the site. The surrounding areas are characterised by the prevalence of historic conservation areas. The site is located on the western side of the Cotton Garden Estate and is known for its public park and distinctive 22-storey Ebenezer, Hurley and Fairford towers. To the north is the Walcot Road Conservation Area with its three-storey terraced houses. To the east is Renfrew Roadside, which contains several listed buildings, including the Magistrates Court, the former Lambeth Fire Station and Workhouse (later converted to Lambeth Hospital) and what is now The Cinema Museum (Mae, 2017). Figure 1 illustrates the location of the project within the urban fabric of London. In response to the unique characteristics and features of the site, the design team developed a comprehensive strategy to integrate the development. Firstly, the scale and massing have been carefully balanced in order to harmonize with the surrounding area. This is achieved through   the use of graduated massing and a deliberate emphasis on the incorporation of open spaces and parks (Mae, 2017). Secondly, the existing transport and vehicular access has been maintained to avoid creating new routes.  Thirdly, a car-free zone has been established, with the number of parking spaces on the site limited to eight, exclusively for residential units. Additionally, a number of bicycle parking bays have been installed to provide secure and convenient storage for cyclists. Fourthly, the "The Walk" concept has been implemented, offering a pedestrian route designed with human needs in mind, in an aim to promote connectivity between the site, parks, buildings, and existing public areas. This includes creating gateways and landmarks to enhance the sense of procession along the footpaths. Moreover, a balanced integration of soft and hard landscape elements was pursued to foster a sense of cohesive connectivity while preserving the site's architectural heritage (Mae, 2017). Figure 2 provides a comparative visual representation of the former site against the proposed design.   Figure 2 provides a comparative visual representation of the former site against the proposed design for Knight’s Walk. From a typological perspective, a total of 84 units have been developed, ranging in size from 54 square metres for the smallest units to 90 square metres for the largest. Phase one comprises 16 flats, including 10 one-bedroom flats, three two-bedroom flats and three three-bedroom flats. In contrast, phase two offers a broader choice with 15 one-bedroom flats, 38 two-bedroom flats and 15 three-bedroom flats. With regard to architectural design, three key design considerations were identified as being of particular importance (HDA, 2022; Mae, 2017). The primary concern was the accessibility of the site for its residents, with particular attention paid to the needs of senior citizens and those with special requirements. This emphasis is particularly pronounced in Phase One, where the majority of units have been designed to meet both the Building Regulations Part M (which provides guidance on access to and use of buildings, including facilities for disabled occupants and easy movement through a building), and the prescribed national standards for accessible spaces (Mae, 2017). Secondly, the efficient use of space was prioritised, with the use of simple and clean architectural lines to optimise the functionality within each unit and the circulation areas. Thirdly, the well-being of residents was a significant consideration, with each unit featuring a terrace overlooking the surrounding green spaces and parks. The overall distribution of flats in both phases is shown in Figure 3.   2. Construction In terms of construction methods, the project adopts a fabric-first approach that focuses on improving the properties of the building fabric, with the objective of optimising thermal performance, airtightness and moisture management. This approach is intended to reduce the necessity for additional mechanical or technical solutions, thereby achieving enhanced energy efficiency and comfort (Eyre et al., 2023). In addition, project planners have incorporated supplementary measures to improve construction processes (Mae, 2017). These include using a reinforced concrete structure in locations prone to thermal bridging, while avoiding cores as the primary structural support system. Furthermore, a strategy to rationalise the building’s "form factor" ensures a coherent visual progression of the building mass whilst mitigating thermal impacts such as overheating on the overall building envelope. Secondly, a balanced glazing ratio has been implemented to reduce direct thermal impacts, with the additional benefit of providing resistance to thermal mass. The use of light-coloured materials also serves to reduce the heat island effect and thermal conductivity between the exterior and interior of the building. Finally, the use of a cantilevered method, particularly in building extensions, reduces thermal bridging while improving the overall aesthetics of the structures.   ​​​​​​​3. Sustainability and energy Several methods to promote sustainability have been integrated into the building’s envelope. The project follows the three-point model known as the "energy hierarchy", which is based on the principles of "Be Lean", "Be Clean", and "Be Green". “Be Lean” emphasizes the planning and construction of buildings that consume less energy. "Be Clean" focuses on efficiently providing and consuming energy, while "Be Green" aims to meet energy needs through renewable sources (Muralidharan, 2021). 3.1. Energy and carbon strategy In line with energy hierarchy models, the project's energy strategy focuses on the building envelope and incorporates high-performance standards recommended by Passivhaus to optimise building mass and thermal boundaries. In addition, provisions have been made to future-proof the buildings by providing provisional spaces for future connection to planned district and central heating systems. Efforts to reduce carbon emissions centre on establishing accurate baseline emissions using the Standard Assessment Procedure (SAP), implementing passive measures such as natural ventilation and high-efficiency appliances, and reducing reliance on fossil fuels for electricity generation through the use of photovoltaic cells as a secondary energy source. As a result, the buildings have achieved a 35 per cent reduction in carbon emissions compared to local regulations and similar developments (Mae, 2017; TGA, 2017). 3.2. Overheating strategy Managing the risk of overheating has become an essential consideration in the design and construction of housing in the UK (Sameni et al., 2015). The quality of the indoor environment in any dwelling, particularly in summer, is vulnerable to excessive solar heat gain which is accentuated by the lack of rapid ventilation measures. To mitigate these challenges, the project's overheating strategy minimises internal heat generation through energy-efficient design and reduces heat gain through careful orientation, shading, windows, and insulation. Passive ventilation measures, such as natural cross-ventilation and fixed external shading, are also utilised. In addition, primary heating pipework is carefully planned to minimise losses, particularly when installed within the dwellings (TGA, 2017). 3.3. Policy and standards The project has been developed in accordance with a complex network of interrelated policies and standards at the national, regional and local levels, in addition to mandatory national sustainability guidelines. Notably, Building Regulations Part L, which sets out specific requirements for insulation, heating systems, ventilation and fuel use, and aim to reduce carbon emissions by 31 per cent compared to those of previous regulations. Knight's Walk introduced a new layer of mandatory requirements, designated as "regional" guidelines. These guidelines are specific to the Greater London area and serve as a reference for all developments. In addition to fulfilling the national and regional regulations, the project had to comply with the requirements set forth by the local councils. Furthermore, the developer's requirements, known as Lambeth's Housing Design Standards function as a clarifying framework, outlining the pertinent policies at the national and regional levels. As a result, the project has comfortably achieved an energy rating of B (based on the Standards Assessment Procedure calculations), with the potential to progress to an A rating. The project has developed a multi-level sustainability strategy and architectural language that considers climate, environment, and local needs, focusing on energy and carbon reduction. These strategies include encouraging active travel, increasing biodiversity and implementing adaptations to mitigate the effects of climate change through a drainage strategy and incorporating SuDS and tree planting. In addition, each flat has been fitted with mechanical ventilation with heat recovery, providing a constant supply of fresh, filtered air even when the windows are closed. All apartments are also equipped with energy-saving electrification systems to minimise electricity consumption (HDA, 2022).   ​​​​​​​4. Reflections The section highlights both the successful aspects and the potential areas for improvement identified in the previous sections by addressing the following questions: What methodologies were deployed within Knight’s Walk that can be classified as exemplifying ‘good’ practise? The comprehensive assessments conducted by the designers, covering a wide range of intervention areas, facilitated the formulation of a responsible phasing strategy that mitigated the social, economic, and environmental risks associated with large-scale development projects. The early provision of alternative, well-built housing for tenants who were displaced has fostered robust collaboration between developers, designers, and local communities. The project was developed in accordance with widely recognised accessibility standards, including compliance with Building Regulations Part M. A comprehensive assessment framework was employed to measure the quality of outcomes in line with national, regional, and local policies. In order to facilitate the adoption of improved energy efficiency strategies, consultation was undertaken with specialists versed in Passivhaus design standards. As a result of this consultation, it was determined that no additional standards were required. These strategies included the implementation of passive measures, such as massing, orientation, and material selection, complemented by high-efficiency mechanical ventilation systems, photovoltaic cells, energy-efficient appliances and well-insulated façade designs. As a result, the project achieved a Class B environmental performance during the operational phase and a diminished average national CO₂ emission for residential buildings by 80 per cent. The project's carbon production averaged 0.7 tonnes of CO₂ per year, with primary energy consumption ranging from 42 to 58 kilowatt hours per square metre (kWh/m2) (DLUHC, 2021). What are the potential weaknesses inherent to Knight’s Walk? Notwithstanding the robust practices that were put in place, several risks were identified, particularly in relation to the design approach that was selected. Although the fabric-first approach is regarded as a fundamental tenet of sustainable construction, it has not been without its detractors. A significant concern is the long-term variability in the performance of fabric-first buildings, which is contingent upon factors such as maintenance practices, occupant behaviour and climate fluctuations. Inadequate construction quality or maintenance practices can result in the deterioration of energy efficiency gains over time, underscoring the need for continuous monitoring and maintenance (Eyre et al., 2023). This could consequently result in a considerable increase in operational costs, thereby jeopardising the objective of housing affordability over the long term. Furthermore, buildings with high insulation using the fabric-first approach may be susceptible to overheating during the warmer seasons in certain climates, particularly if passive cooling strategies are inadequately integrated into the design (Eyre et al., 2023). This can lead to additional energy consumption for cooling purposes and counteract efforts to achieve highly efficient energy.

South Yorkshire Housing Association manages 6,000 homes to provide social and affordable rent housing for over 10,000 residents (SYHA, n.d.). The housing association is helping to lead the way in less conventional construction methods, utilising industrialised construction to deliver a portion of its homes. As a founding member of the Off Site Homes Alliance (OSHA, n.d.), SYHA is also part a framework and network of registered housing providers, local authorities, contractors, and strategic partners, dedicated to delivering high-quality, affordable housing produced using both 2D panelised and 3D volumetric approaches. The two semi-detached WikiHouses, with an approximate floor area of 70m², are situated in Sheffield, close to the city centre. They were delivered in collaboration with product design providers Open Systems Lab, architects Architecture 00, engineers Momentum, manufacturers Chop Shop, and assembly and installation were carried out by Castle Building Services supported by Mascot Management. The project is not only exemplary in reducing embodied energy in housing but also proves to be energy efficient, having earned runner-up in the Ashden Awards for Energy Innovation. Design WikiHouse aims to democratise housing with the creation of standardised and open-source designs incorporating industrialised construction, based on foundational principles such interoperability and a lean approach inspired by the Toyota Production System (WikiHouse, n.d.-a). WikiHouse provided SYHA with a “jigsaw of pieces” in the form of panelised components designed to be assembled around a framing system. The system was made from simple plywood construction, with no need for steel due to the proposed low building height. Timber is not only ideal for buildability and deconstruct-ability as a lightweight material, but it also possesses carbon sequestering properties. It should be noted the open-source product can be limiting for some adopters of WikiHouse as additional design, construction and installation services are not included. SYHA therefore needed to fill the gap between the product and delivery to their end-users. Manufacturing WikiHouse products lend themselves to self-build construction or utilisation of ‘micro’ factories. SYHA’s pilot used localised construction to manufacture the plywood frame using digital files, cut by CNC machining company ‘Chop Shop’, located just 1 mile from the site (Plowden, 2020). Cutting the pieces was a fast and efficient process, which was designed to minimise material waste. Chop Shop also assisted by storing the building parts until the site was ready for assembly due to the lack of on-site storage space. WikiHouse seems to be well suited to manufacture by a distributed network of small manufacturers. However, according to SYHA, there is potential for scalability with larger housing association schemes in future. In addition, the production strategy is ideal to unlock small, tricky sites within the housing association’s portfolio, facilitating the production of high-quality housing with high circularity potential. Transport and assembly The dimensions of the timber frames were small enough to be delivered to site using a transit van rather than a larger lorry, which proved to be more manageable and cost effective. Once on site, the prefabricated building parts were assembled “like a jigsaw” using a step-by-step manual, although SYHA felt the instructions could be enhanced in the future to improve delivery by a range of stakeholders (Plowden, 2020). The project programme was much shorter compared to a traditional build, the first home was manufactured and assembled in under a month. This process was even faster for the second home due to the experience gained from the first home, highlighting potential to improve efficiency for larger schemes in the future. As prefabrication and assembly are still unconventional, the transition between these processes may present additional complexity for the stakeholders involved compared to a traditional build. In the case of SYHA’s WikiHouse, Miranda found “the manufacturer saw its job as providing the cut pieces for the installer to install, they didn't appreciate that they were part of a manufacturing process with the installer”. She went on to highlight that manufacturers and installers are typically separate parties in the UK, with installers often being main contractors who aren’t used to off-site methods. The team also had to overcome issues with unexpected ground conditions which hadn’t been included within the original site survey, though this was unrelated to the construction system used. Building performance SYHA’s WikiHouse homes have so far proven to be warm and energy efficient, resulting in low energy bills for residents, owing to the high-level of insulation within the plywood structure and panelling. The building strategy ensures easy maintenance and access during the use phase without disturbing residents. This was achieved by incorporating exterior services coupled with dry construction techniques. As a result of their involvement in the whole process, SYHA is able to effectively manage disassembly for future maintenance and potential adaptations, as their Home Maintenance Team were able to observe how the WikiHouses were assembled. Legal Providing the design and detailing are correctly implemented, meeting UK building regulations is not an issue with the WikiHouse system, which claims its products will exceed the requirements of UK building regulations (WikiHouse, n.d.-b). However, it proved more difficult to obtain the building warranty for the SYHA pilot. All new products need to be warranted, which requires warranters to inspect the whole building process to guarantee the necessary requirements are met. SYHA’s WikiHouse utilised the Buildoffsite Property Assurance Scheme (BOPAS) (n.d.), which is a specialist warranty provider for buildings using industrialised construction, referred to as Modern Method of Construction (MMC) in the UK. Homes with BOPAS accreditation are readily mortgageable for a minimum of 60 years. Financial Using an off-site approach can be financially advantageous, as more time is invested upfront to plan, design, and manufacture. This shortens the time spent on-site and therefore reduces preliminary costs for the operation of the construction site. Although the project benefitted from a shortened timeline due to the industrialised approach, the WikiHouse system ultimately proved to be more expensive than a traditional build. According to Miranda, the cost of the completed homes was approximately 33% higher than a traditional build but she estimates if they were to build using WikiHouse again - taking on-board lessons learnt - the premium would reduce to 12% (Plowden, 2020). However, there is hope for the WikiHouse system to become a more financially competitive alternative to traditional build in the future. For this to happen, Miranda suggests improving efficiency of the assembly process, particularly with faster utility connections. Additional financial viability could also be achieved if the system were to be applied to larger sites. In regard to a life cycle costing approach, Miranda believes it is too early for SYHA to say whether the WikiHouse pilot will prove to be cheaper than a traditional build in the long-term.