Life-cycle assessment of the built environment tends to focus mostly on operational final energy consumption of buildings located within a specific context. Such limited scope prevents a broader usability of findings in practice. In Switzerland, the "2,000-Watt society" vision provides a theoretical framework towards energy transition. Intermediate targets for 2050 relate to an extensive assessment incorporating environmental impacts of construction materials and use of a building, and of induced mobility of its occupants. Accordingly, it becomes crucial to gather information about the current building stock performance and its transition potential. The paper aims at contributing to the sustainability transition debate by providing a comparative assessment of retrofitted and new residential buildings representative of the Swiss building stock. A direct output could constitute in establishing a reliable reference dataset to support practitioners' or lawmakers' future decisions. The novelty of the study relies on two aspects: 1-on adopting an interdisciplinary approach to propose an overview of the current status and transition potential of the built environment; 2-on building a methodology able to extrapolate results for large-scale studies of neighbourhoods or larger built areas. Based on the definition of four building archetypes, this study assesses four scenarios decomposed into four to six variants. The scenarios consist in varying the building energy-performance, while the variants implement different locationsamong urban, peripheral and rural areasand different passive or active strategies. Results are expressed in terms of non-renewable primary energy consumption and global warming potential. They highlight in particular the performances of renovation projects, the effect of high-energy performance on embodied impacts, the low-level of performance of single-family houses and the significant impact of mobility related impacts.

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In Switzerland as in most european countries, the last decades of urban development have put much pressure on the environment due to uncontrolled urban sprawl. The existing peripheral residential built-up areas mostly composed of single-family houses are responsible for and subjected to many sustainability issues, which are expected to grow in the short/medium term. focusing on urban and architectural design, this on-going research investigates possible paths for the future of peri-urban neighbourhoods of single-family houses by 2050. The paper presents the intermediary results of several test-applications of prospective scenarios developed for two case studies in the urban region of lausanne, Switzerland. first, this article briefly introduces the research framework of the periurban question in Switzerland by highlighting the specificities of the policy and territorial contexts. Second, it describes the design framework, focusing on the elaboration of a typology of peri-urban neighbourhoods of single-family houses used as a preoperational tool to guide the design process. The core of the paper then focuses on the conceptual elaboration of four prospective scenarios foreseeing possible evolutions for peri-urban neighbourhoods of single-family houses. To illustrate this approach, test-applications -in terms of urban and architectural design -are conducted in two existing neighbourhoods. finally, a limited list of indicators on density, land use and environmental impacts helps assessing the performances of each applied prospective scenario. The scenarios seek to be operational and feasible in a way to provide a decision support. The preliminary conclusions of the study highlight several initial conditions to bring peri-urban neighbourhoods on a path towards sustainability transitions.

Peri-urban neighborhoods of detached houses are facing countless challenges related to the building stock’s low energy efficiency, to the current demographic transition reducing household size and increasing the proportion of elderlies, to their distant location combined with exclusive residential use and few public transportation services. Those challenges represent growing issues for the upcoming years, with regard to the role those neighborhoods have to play in contributing to the collective challenge of the energy transition and to the fact they would have to cope with eventual future crisis. Hence the research investigates the transition potential of existing peri-urban neighborhoods of detaches houses by 2050, in Switzerland. Through a more focused approach, the paper, complemented with a poster, aims at highlighting how future evolutions might affect the overall sustainability of those residential areas. To do so, it focuses on the multicriteria assessment of five scenarios envisioned for peri-urban neighborhoods of detached houses and applied in six Swiss case-studies by 2050. The scenarios Caducity and Exclusivity follow business as usual trends. The scenario Opportunity investigates the effects of soft-densification processes, and Urbanity and Mutuality offer new perspectives towards densification or landscape integration. A multicriteria comparison relies on results of the systematic assessment of the neighborhoods’ environmental quality, energy efficiency, economic viability and social diversity in 2050 and of the scenario’s feasibility. It innovates by relying on a spatiotemporal assessment methodology developed at neighborhood scale. Altogether it provides a qualitative decision-making support by identifying strengths and weaknesses of each scenarios. The overall average results show that Urbanity, which concentrates its actions on a few plots, presents the best-balanced performances among all criteria. All the other scenarios are favorable to one or two criteria only. Besides providing decision-making support, this assessment also sets a framework to reorient public policies towards more resilient peri-urban residential neighborhoods.

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