Aya Elghandour

In the Nordic countries, water-related damages in buildings (including homes) result in annual costs of several billion euros. These damages emerge from leaks in piping systems, inadequately waterproofing wet room layers, or damp-related problems which also negatively impact indoor air quality and occupants’ health. Some measures can be implemented to enhance the building sustainability that could result in huge savings and have a better impact on the environment and occupants’ health. The Swedish insurance company “Dalarnas Försäkringsbolag” decided to finance this research project to look for solutions to foment a more economically and environmentally sustainable future for housing (Magnusson, 2020; Petrović et al., 2021). In collaboration with the Dalarna University, a design competition for students was announced in 2017 (Dalarna University, 2020). The winning team proposed an aesthetically pleasing design which was also rational and sustainable. In 2019, Dalarnas Villa was constructed by high school students under the supervision of local entrepreneurs. Currently, it is rented out to a Swedish family (Dalarna University, 2020). The Dalarnas Villa received the Nordic Swan Ecolabel which is the Nordic official environmental label (Holén, 2019; Svanen, n.d.). Construction and materials Dalarnas Villa was an opportunity to test the use of sustainable materials and smart systems to augment safety and save energy by way of cost-effective solutions with less negative environmental impact (Magnusson, 2020; Petrović et al., 2021). Wood is considered to be a sustainable option in Sweden. Thus, the house structure system is based entirely on wood. For the façade, wood panels were utilized as well. For the energy and smart systems, they installed photovoltaic panels on the southwest side of the roof; an exhaust air circulation system, and a ground source heat pump. Each year, a new ventilation system is installed to test different solutions to improve indoor air quality and provide energy savings. For safety systems that mitigate water-related damages, they used a smart water control system. It has a switch that detects, alerts, and closes the water supply if there is a leak, no occupants in the house, and/or in case of potential risk or damage due to water freezing (Dalarna University, 2020; Magnusson, 2020; Petrović et al., 2021). Life Cycle Costs assessment Life Cycle Costing (LCC) calculates the costs that are incurred during the pre-construction and construction phases (known as initial costs) and the future maintenance and operational costs (Estevan & Schaefer, 2017). LCC applies discounts and inflation rates to keep future costs in line with those of today. In other words, to bring all initial and future costs over a project lifetime into a single time dimension (Jawad & Ozbay, 2006). Petrović et al., (2021) conducted LCC analysis for the Dalarna Villa from cradle to grave following the lifetime structure of EN 166 27 standard. Over a 50-year lifespan, a discount of 7% and an inflation rate of 2 % and adding the taxes, the life cycle costs of the Villa accounted for 3,588 euro/m2. LCC conducted the study for 50- and 100-year lifespans as well as different inflation and discount rates. Over the two life spans, a common pattern has been detected: The investment-related costs had the highest share. Within these investment-related costs, labour amounted to half of the costs in this life cycle stage, followed by building materials, installations, and other pre-construction costs. This resonates with the ongoing issue of labour availability and the rise in construction prices in Europe as shown in the Eurostat chart presenting the EU construction prices and costs index (CCI) (Eurostat, 2021). This high percentage emphasizes the crucial potential of the industrialized construction sector to reduce construction labour (Qi et al., 2021), which is the research focus of ESR 01.  The running costs during the occupation phase - when residents were living in the house - included maintenance, replacement, operational energy and operational water costs. In this phase, maintenance costs were the highest, followed by replacement costs. After 50 years, both maintenance and replacement costs significantly increase, while the operational energy and operational water costs rise slowly (Petrović et al., 2021). The study also showed that without installing PV panels, the operational energy use costs would almost double over the 100 year lifespan. For the end-of-life costs, the study assumed the villa would be demolished. Thus, these costs were the only value that is decreasing over the 100-year life span. If it were designed to be dismantled, the end-of-life costs would increase, but the solution would be more sustainable with regard to resource efficiency and environmental impact (Petrović et al., 2021). Design for disassembly is the research focus of RE-DWELL ESR01 project. Over a 100-year lifespan, the initial costs of pre-construction and construction accounted for almost 75% of the total LCC, while the operational costs of maintenance, energy and water accounted for almost 25% (Petrović et al., 2021).* Environmental impact The carbon footprint of building materials can be understood through the so-called Global Warming Potential (GWP). It is an indicator of the amount of the greenhouse gases (GHG) that trap heat in the atmosphere (Durkee, 2006). This amount is explained in comparison with a reference gas which is  carbon dioxide. Petrovic et al., (2019) carried out Life Cycle Assessment (LCA) with a focus on the villa building materials and their transportation distance to understand their environmental impact. The study calculated the GWP using One Click LCA software. The conclusions were that the thermo wood material used in the exterior envelope releases the highest amount of GHG to the atmosphere compared to the other materials which account for 514.03 Kg CO2e/m3. The next materials were concrete, cross-laminated timber (CLT) and the triple glazed windows releasing 268.68 Kg CO2e/m3, 140 Kg CO2e/m3 and 115 Kg CO2e/piece respectively (Petrovic et al., 2019). On the other hand, the wood-based materials for the structure and envelope are lower in GWP where each account for 25 Kg CO2e/m3. Thus, they can be considered more environmentally friendly. Dalarnas Villa is a pilot project to investigate sustainable housing solutions in Sweden; houses that prioritise the quality of the indoor environment, the health of the residents and the impact on global warming. However, one of the questions to be addressed in the future is whether the increased costs of sustainable solutions will be cost-effective in the long term, as residents will pay less for maintenance and energy costs.

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.

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.