The 2050 decarbonization goals coupled with the growing housing shortage in Europe intensify the pressure on new-build dwellings to enhance their energy performance. Beyond a zero operational energy, the focus has shifted towards reducing embodied carbon (EC). Against this backdrop, this study investigates the simultaneous impact of downsizing and the use of timber in new-build dwellings, EC reduction strategies seldom explored concurrently. Through partial life cycle assessments, three scenarios are modelled: the Small, Medium, and Large House, with two construction variations for each, comparing a modular timber design to a conventional concrete alternative. Designs are based on dwellings built in Almere, the Netherlands. Data is extracted from the Swiss Ecoinvent database using the TOTEM tool and the static −1/+1 approach for biogenic carbon accounting is adopted. Results show a total EC ranging from 42,608 to 70,384 kgCO2eq for the timber designs versus 54,681 to 91,270 kgCO2eq for their concrete counterparts. Findings suggest that the relationship between house size and EC is sublinear whereby a house twice the size entails less than twice the EC emissions. Only the simultaneous implementation of downsizing and the use of timber achieved 53% carbon savings. The discussion explores implications of outcomes across academic, industry and policy perspectives, challenges in implementing smaller timber dwellings, and study limitations and future research. Beyond its empirical contribution, this paper offers a practical contribution with its hierarchical data analysis approach covering building, element and component. This approach can be implemented by researchers and practitioners alike to inform their design process.@en

This thesis examines the potential of small, low-carbon, (near) zero-energy dwellings as a solution that would both address sustainability challenges and answer to the growing housing shortage in North-West Europe. It adopts a multidimensional outlook that encompasses institutional, social and technical aspects surrounding the dwellings. The institutional aspect is addressed through an investigation of financial, legislative, technical and cultural barriers to the implementation and uptake of small, low-carbon, zero-energy dwellings. A context specific approach is adopted taking into account contextual peculiarities for the formulation of more refined policy suggestions. The social dimension is addressed first from the perspective of market supply through an investigation of the perceptions of housing professionals. The distinction between perceived versus actual barriers identified by housing professionals is made highlighting a potential desynchronization between policy developments and local practice. Accordingly the study calls for innovation in information dissemination between policy and local practice and between housing professionals themselves. The social dimension is then addressed from the perspective of market demand through an investigation of consumers’ current housing preferences. The assumption stating that, due to an increase in smaller, elderly, and lower-income households, current housing preferences are leaning towards smaller dwellings is refuted underlining the importance of distinguishing between smallest and smaller dwelling sizes. Lastly, the technical dimension is addressed through conducting a partial life cycle assessment that focuses on the embodied carbon of the dwellings. Both downsizing and the use of low-carbon materials such as timber are investigated as embodied carbon reduction strategies. Together, the three dimensions provide a holistic evaluation of the potential of small, low-carbon, zero-energy dwellings as a solution while addressing the complexity in reaching sustainable outcomes.@en

In 2010, the Energy Performance of Buildings Directive announced that all new buildings are to be nearly zero-energy as of January 2021. Having reached year 2022, it can be said that the transition has proven to be slower than anticipated. Transition research has long acknowledged the potential impact of the human factor in the process of change. While there is a relative wealth of literature on end-users and their perceptions as recipients of change within the demand end of the market, research on professionals and their perceptions as actors in the process of change is limited. Thus, this study looks at the human factor in the supply end of the market by bringing professionals’ perceptions to the forefront in its investigation of barriers to the implementation and uptake of nearly zero-energy housing in practice. As part of the project entitled Housing 4.0 Energy: Affordable and Sustainable Housing through Digitization, data were collected through a focus group and semi-structured interviews with housing professionals in Kilkenny, Ireland. Descriptive coding, inferential coding, and fact tracing revealed several identified barriers to be perceptions and not actual barriers to nearly zero-energy housing. Additionally, information dissemination and assimilation between policy and industry was identified as an overarching barrier. Therefore, the paper ends with recommendations to reduce delay factors at the supply end of the market, thus contributing to closing the gap between the development of policies and their implementation@en

After more than ten years since the introduction of Near Zero-Energy Buildings (NZEBs), the transition towards a zero-energy new built environment can still be considered slow despite European Member States’ various efforts to facilitate, promote and accelerate their implementation and uptake. The barriers to sustainability measures in general and NZEBs in particular have been extensively explored by academic literature and despite different research scopes, perspectives, locations and times, previous studies have reached similar outcomes. Similar barriers were perceived by different housing professionals in different geographic contexts and these same barriers also persisted through time. This study argues that while this could be interpreted as a validation of outcomes, it also underlines a limitation resulting from a general level of analysis. Thus, this study contributes to the discussion by adopting a context-specific approach in its investigation of barriers to near zero-energy housing in small towns in Flanders, Ireland and the Netherlands. The data was collected from a series of focus groups with housing professionals in Leuven, Kilkenny and Almere. Through descriptive coding, this study’s outcomes echoed previous research findings. However, a closer look through inferential coding resulted in the identification of 21 new contextual barriers leading to the formulation of more specific policy suggestions with a different allocation of precedence that depends on every context@en

Despite efforts to promote and accelerate the adoption of innovative, affordable, and zero-energy dwelling solutions, the number of dwellings complying with standards such as the EPBD remains relatively low as we reach year 2020. Studies have already explored potential challenges and opportunities to the uptake of such designs. However, despite previous findings and recommendations, the market's response remains slow. Building on existing knowledge and as part of the Housing 4.0 Energy project, this study investigates current financial, cultural, legislative and technical barriers and drivers to the implementation and uptake of small, innovative, affordable, zero-energy dwellings in small towns in Belgium and Ireland. Focus groups gathering housing providers, decision makers, stakeholders, and contractors were conducted in Leuven and Kilkenny. Outcomes revealed that participants' general perceptions around barriers and drivers are similar between the two countries and are validated by previous research findings. However, a closer look at context specific barriers reveals considerable differences. The identification of these contextual differences enables a better apprehension of the current situation in every location leading to the formulation of context specific recommendations and a better allocation of precedence. Thus, this paper demonstrates the importance of context specific investigations not only in the identification of challenges to energy efficiency innovations but also in establishing more effective implementations.

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