ReMoTe-S. Residential Mobility of Tenants in Switzerland: an agent-based model

Accounting for a fourth of the CO2 emissions and total energy consumption in Switzerland (IEA, 2018), housing plays a crucial role in the transition towards the sustainability of urban systems. Although new technologies have been developed to tackle the environmental burden of the residential sector, technical solutions alone are not sufficient to achieve the transition, as their success depends on how they can be reconciled with the present and future needs of households. Residential mobility offers the perfect ground to understand the matching of and recursive effect between households needs and dwellings. A wide range of models simulating residential dynamics exists; however, the specificities of the Swiss rental market require to consider factors influencing the decision to move and the selection of the new dwelling that are tenure- and context-specific, and which have not been modeled so far. In our presentation, we introduce ReMoTe-S, an agent-based model of the residential mobility of tenants in Switzerland. The model results from the interdisciplinary scientific collaboration of social, environmental and computer scientists. Based on exploratory qualitative and quantitative research, ReMoTe-S accounts for the complexity of tenants’ and buildings’ life course. The former includes changes in household (e.g. a new child), housing (e.g. an offer on the market), and work trajectories (e.g. a promotion), the corresponding triggers to move, and the consequent adjustment of residential preferences. The latter considers the construction, renovation and demolition of dwellings and buildings of two types of Swiss multifamily housing providers: cooperatives and asset managers. The matching between household- and dwelling-agents is determined by preferences and constraints. Preferences are simulated as desired housing functions (e.g. a shelter, a status symbol); their correspondence with the function fulfilled by the dwelling is used to determine households’ satisfaction, and thus the relocation behavior. While the desired function is specific to each household type (e.g., ‘young single’), the dwelling function is computed from the dwelling, building and neighborhood characteristics (e.g., ‘proximity to public transports’). Constraints are set based on rules specific to the Swiss rental market (e.g., occupancy rules, salary-rent proportion). The model simulates an open market, where in- and out-migration are responsible for the variation in dwellings’ vacancy rate. To check for plausibility and robustness of the baseline scenario, calibrate the model and run experiments, the effect of the variation of several parameters were explored. Our presentation shows the results of the OFAT or One-Factor-at-a-time sensitivity analysis, where, to account for the stochastic variation of parameter values and estimate long term behaviours independent of initial patterns, each simulation run was repeated 100 times over a time span of 30 years (or 360 time-steps). In this context, two what if experimentations are briefly presented, aimed at investigating the reciprocal effect of household preferences on dwellings in the framework of housing sustainability. The first explores how variations in the size of shared flats influence individual space consumption in unpredictable ways; the second looks at changes in vacancy rate resulting from changes in the characteristics of new dwellings on the market. The final goal of the presentation is to discuss with the audience the last crucial step before the model is available to be shared, integrated and used: the validation. This phase is strongly debated in the literature on ABM, which offers a large amount of possibilities. The introduction of the model, its verification, and the two what if experimentations will be used as a base to discuss the following questions: Against what would this empirical agent-based model be validated? Which approach would be the best to validate it? Should the validation occur now, or in a later stage? The last question refers to the larger scope of the model. More precisely, ReMoTe-S was conceived as one piece of a larger interdisciplinary collaboration, where the ABM of households’ residential mobility would be integrated with a second one, simulating more accurately owners’ strategies (i.e. investment, demolition), and a third one, calculating the resulting environmental footprint. The integration of these three models would allow for the exploration of scenarios that take into account, simultaneously, the socio-cultural, economic and environmental aspects of housing’s sustainability.

Agent-based modeling for studying the choices of households in Switzerland

Claudia Rebeca Binder Signer, Anna Pagani

Housing plays a fundamental role in the transition towards a more sustainable society. In Switzerland, the unbalanced relationship between environmental, economic and social factors manifests itself in the current market trends of rental apartments, where data show a discrepancy between demand and supply. In fact, the impossibility for the supply to actively anticipate the change in tenants’ housing preferences often results in residential redistribution and new demand pressure. In this context, we have identified the following gaps: (i) Supply responds to the fast change in society (e.g., new family’s structure, lifestyles and comfort levels) with short-term satisfactory solutions. However, their long-term impact leads to a mismatch with the future evolving demand. In fact, the lack of understanding of system dynamics often causes actors to react to the system’s outputs, and to neglect the structure responsible for a specific behavior. Understanding the system structure is key to recognizing patterns, and to propose sustainable solutions accordingly. Therefore, studying the way tenants make decisions concerning their residential mobility is fundamental to design scenarios based on the system’s dynamics and to provide support for policy-makers, practitioners and households. (ii) Research on residential mobility and location choices is often fragmented in disciplinary silos, prioritizing the role played by housing characteristics (e.g., size, location, view) as determinants of decisions for the selection of a new dwelling. However, going beyond disciplinary fragmentation, housing function can be considered as the most crucial determinant of the system’s dynamics. Considering the lack of interdisciplinary and systemic approaches to housing and the related difficulty of the sector to predict and adapt to changing needs while providing sustainable solutions, the research aims to develop a model representing the way households take decisions concerning their residential situation. This allows to evaluate and propose measures supporting the transition towards housing sustainability in Switzerland. To fulfill this goal, a conceptual framework is developed, representing the factors influencing tenants’ decisions to move and where to move. From the framework, decision-making rules are derived, which allow for developing an Agent-Based Model (ABM) simulating tenants’ relocation decisions. To run the model, quantitative data on buildings and households are gathered from the database of our three partners: the cooperatives SCHL and ABZ and the insurer and asset manager Swiss Mobiliar. With the support of the qualitative findings of two Group Discussions with our partners’ tenants in Vaud and Zurich, we will conduct a large survey. Its results will feed into the model allowing, together with the behavioral rules, for simulating the interplay between households and dwellings. The Agent-Based Model of households’ residential decisions will feed an interdisciplinary collaborative model including social, economic and environmental factors as well as demand and supply requirements. The resulting baseline scenario will be used for the simulation of policy changes and the identification of new paths for the transition towards a more sustainable housing. These paths will be developed and assessed with a transdisciplinary approach involving our three partners and the Federal Housing Office, with the aim to propose a set of agreed policy recommendations for property owners as well as cantonal and federal authorities.

2018

Towards sustainability through housing functions: a systems perspective for the study of Swiss tenants' residential mobility

Anna Pagani

Problem. Housing is a major contributor to Switzerland's carbon footprint and energy consumption, but it is also a basic need. Research on climate change mitigation strategies has so far paid insufficient attention to households' preferences and their contribution to housing sustainability. Depicting residential preferences requires an understanding of the multilevel, context-specific, and interrelated determinants of the match between households and dwellings, which are made explicit in the residential mobility process.Goal. The goal of this thesis is to clarify the determinants of residential mobility and their interrelations to illuminate the effects of measures aimed at reducing housing's environmental footprint while meeting the needs of its households. Methods. This research employs a systems and transdisciplinary approach to explore, dig into and disentangle the complex relations governing the residential mobility process. It starts by conceptualising residential preferences and dwelling forms as the manifestations of the housing human and material subsystems, which are determined by the system's function. The applicability of this framework to residential mobility is explored by sequentially gathering and integrating qualitative and quantitative data on the tenants of three Swiss multifamily housing owners. This empirical basis is used to develop an agent-based model (ABM) of households' residential dynamics for the exploration of the emergent effects of housing sustainability measures.Results. Firstly, the present work shows that several functions coexist in the housing realm, each of which determines, for given elements of the societal and environmental supersystems (e.g. culture, location), different residential preferences and dwelling forms. Secondly, empirical investigations demonstrate that the notion of function offers analytical support to the study of Swiss tenants' residential mobility, as it permits the identification of linkages between the qualities of residential environments and residents' characteristics, their residential satisfaction, and triggers to move. In particular, functions help explain the observed preference for larger dwellings and the low propensity of shrinking households to relocate. Furthermore, this notion enables the observation of the effects of the exceptional circumstances posed by the COVID-19 on residential preferences, and the increased desire for a place for 'self-representation'. Lastly, using this empirical and context-specific knowledge, the thesis introduces the agent-based model ReMoTe-S. Simulation experiments show that measures to reduce space consumption are insufficient if not accompanied by an offer of dwellings that simultaneously meet and reshape households' preferences. They also reveal that these preferences cannot be fulfilled via the direct correspondence between desired and current housing characteristics, as housing functions result from several compromises between them. These results invite practitioners and citizens to collectively reimagine the way housing functions express themselves in dwelling forms with a lower environmental footprint.Conclusions. This thesis offers a platform for systemic co-inquiry that enables researchers and practitioners to navigate the complex interactions at play for the provision of sustainable housing. To limit human-induced global warming, the approaches and tools used must rapidly permeate practice and teaching in architecture.

EPFL2022

Methodology for the identification of promising integrated biorefineries

Ayse Dilan Celebi

Steady increase in global energy consumption, greenhouse gas emissions, and depletion of fossil energy resources, together with increased attention towards sustainable development has prompted researchers to discover economical and environmentally competitive non-petroleum alternatives and biomass is considered to be one of the most promising renewable sources of energy and carbon of this matter to address the aforementioned issues within a biorefinery platform. A biorefinery is an integrated processing facility that converts biomass into transportation fuels, value-added chemicals, heat, and electricity via biochemical and thermochemical conversion routes. Integrated biorefineries are capable of mimicking petroleum refineries via application of advanced process synthesis methods including modeling, simulation, integration and optimization techniques. This thesis presents a comprehensive synthesis methodology for the integration of bioprocessing technologies in biorefineries by addressing techno-economic and environmental sustainability analysis. The proposed systematic design approach combines advanced process modeling approaches, process integration techniques, and multi-objective optimization algorithms to assess the performance of the overall system with respect to economic, environmental, and energetic indicators. The design strategy is applied based on different case studies. Results indicate that multi-product processes can yield significant cost and environmental benefits. Additionally, the integration of biochemical and catalytic processes with thermochemical conversion pathways results in increased carbon efficiency and economic and environmental competitiveness. Synergies between biorefineries and energy system are assessed by integrating industrial plants with a cogeneration system producing biofuels and process heat. In doing so, system efficiency is increased by coupling the proposed cogeneration system with carbon capture and sequestration (CCS) and power-to-gas technologies to store the renewable intermittent electricity in the form of biofuels. The results exhibit that through system expansion, integrated biorefinery systems allow us to imitate fossil refineries with a large spectrum of bio-based products. This further increases the resource efficiency while offering a promising solution to mitigate CO2 emissions and hence reaching the longer-term decarbonization target set by the Paris Agreement.

EPFL2019