EPA: Multi-Modelling for Complex Challenges With the acknowledgement of international grand challenges, the demand for better and ever more complex models is likely to increase a manifold. Where single models may no longer be able to grasp the complexities of a system, multi-modelling (Nikolic, Warnier, et al., 2019; Vangheluwe, 2000) enables the combination of the strengths of different models whilst enabling the development of multi-perspective insights. In this research, I developed a multi-model to provide policymakers in The Netherlands with insights on how to steer the Urban Energy Transition at both national and municipal level. This is done by combining a System Dynamics (Forrester, 1961) model for evaluating market behaviour at the national scale, and an Agent-Based Model (Epstein & Axtell, 1996) for investigating investment behaviour at the neighbourhood level. The results from experiments with this model show that multi-perspective insights can be very helpful in designing policies and strategies for dealing with Sustainable Urban Development. It is found that challenges concerning the conceptualisation phase of the Model Development Cycle, could turn out to be opportunities for model development. As formalism selection and possible overlapping scales between models requires extra effort and attention, this attention results in model concepts that will be better evaluated, resulting in better concepts to be developed altogether. The main challenge that is currently unresolved, is that of the computational performance of multi-models. Although worsened by the choice for Agent-Based Modelling as one of the formalisms used in the multi-model, the computational requirements for the simulation seriously hamper the opportunities for experimentation and analysis. Although solutions can be found to minimise the computational demand or the effects of it, improvements are required in either computational demand or processing supply, for multi-models to become a suitable method for common modelling and simulation practice. CME: Energy Transition in the Built Environment With the EU goals (European Commission, 2018b) to reduce CO2 emissions to zero tons in 2050, The Netherlands has set up a climate agreement (Klimaatakkoord, 2019) in which municipalities get a leading role in reducing the carbon footprint of the Built Environment. To realise these goals, an energy transition is inevitable and strategies need to be developed for remodelling neighbourhoods into sustainable living environments. Before the end of 2021, municipalities have to come up with a plan in which they decide what neighbourhoods will be transformed and when. A problem in this is that currently, municipalities do not have the resources and tools to do so (RTL, 2019; Schuttenhelm, 2020; Straver, 2019). Currently, existing models, such as the Vesta MAIS model (Planbureau voor de Leefomgeving, 2019c) offered by the national government, are missing two crucial aspects which should help municipalities to set up their strategies: time dynamics and population dynamics. The techno-economic approach does present the ’best’ solution but is missing how to get there. Next to this, uncertainty around national policies makes that it is very difficult to decide on a robust policy. To deal with the aforementioned challenges, I use a multi-modelling approach (Nikolic, Warnier, et al., 2019; Vangheluwe, 2000), using System Dynamics (Forrester, 1961) and Agent-Based modelling (Epstein & Axtell, 1996) in which on the one hand, the time dynamics and population dynamics aspects are incorporated, and on the other hand multi-perspective insights on effects of national policies on national goals as well as insights on the heterogeneous effects at the municipal level are provided. An important finding is the crucial role of a CO2 tax on the realisation of national goals. Without this tax, homeowners and housing corporations will not be motivated sufficiently to significantly invest in insulation measures, making that fewer alternative heating systems will be implemented. Next to this, it is found that major differences can be distinguished between rural and urban areas. Heating grids will be a viable starting point for urban municipalities to start their transition due to the availability of residual heat. For rural municipalities, this will be more difficult due to a dependency on low-temperature systems. There, starting with the neighbourhoods that have the most potential to insulate is advised.

EPA: Multi-Modelling for Complex Challenges With the acknowledgement of international grand challenges, the demand for better and ever more complex models is likely to increase a manifold. Where single models may no longer be able to grasp the complexities of a system, multi-modelling (Nikolic, Warnier, et al., 2019; Vangheluwe, 2000) enables the combination of the strengths of different models whilst enabling the development of multi-perspective insights. In this research, I developed a multi-model to provide policymakers in The Netherlands with insights on how to steer the Urban Energy Transition at both national and municipal level. This is done by combining a System Dynamics (Forrester, 1961) model for evaluating market behaviour at the national scale, and an Agent-Based Model (Epstein & Axtell, 1996) for investigating investment behaviour at the neighbourhood level. The results from experiments with this model show that multi-perspective insights can be very helpful in designing policies and strategies for dealing with Sustainable Urban Development. It is found that challenges concerning the conceptualisation phase of the Model Development Cycle, could turn out to be opportunities for model development. As formalism selection and possible overlapping scales between models requires extra effort and attention, this attention results in model concepts that will be better evaluated, resulting in better concepts to be developed altogether. The main challenge that is currently unresolved, is that of the computational performance of multi-models. Although worsened by the choice for Agent-Based Modelling as one of the formalisms used in the multi-model, the computational requirements for the simulation seriously hamper the opportunities for experimentation and analysis. Although solutions can be found to minimise the computational demand or the effects of it, improvements are required in either computational demand or processing supply, for multi-models to become a suitable method for common modelling and simulation practice. CME: Energy Transition in the Built Environment With the EU goals (European Commission, 2018b) to reduce CO2 emissions to zero tons in 2050, The Netherlands has set up a climate agreement (Klimaatakkoord, 2019) in which municipalities get a leading role in reducing the carbon footprint of the Built Environment. To realise these goals, an energy transition is inevitable and strategies need to be developed for remodelling neighbourhoods into sustainable living environments. Before the end of 2021, municipalities have to come up with a plan in which they decide what neighbourhoods will be transformed and when. A problem in this is that currently, municipalities do not have the resources and tools to do so (RTL, 2019; Schuttenhelm, 2020; Straver, 2019). Currently, existing models, such as the Vesta MAIS model (Planbureau voor de Leefomgeving, 2019c) offered by the national government, are missing two crucial aspects which should help municipalities to set up their strategies: time dynamics and population dynamics. The techno-economic approach does present the ’best’ solution but is missing how to get there. Next to this, uncertainty around national policies makes that it is very difficult to decide on a robust policy. To deal with the aforementioned challenges, I use a multi-modelling approach (Nikolic, Warnier, et al., 2019; Vangheluwe, 2000), using System Dynamics (Forrester, 1961) and Agent-Based modelling (Epstein & Axtell, 1996) in which on the one hand, the time dynamics and population dynamics aspects are incorporated, and on the other hand multi-perspective insights on effects of national policies on national goals as well as insights on the heterogeneous effects at the municipal level are provided. An important finding is the crucial role of a CO2 tax on the realisation of national goals. Without this tax, homeowners and housing corporations will not be motivated sufficiently to significantly invest in insulation measures, making that fewer alternative heating systems will be implemented. Next to this, it is found that major differences can be distinguished between rural and urban areas. Heating grids will be a viable starting point for urban municipalities to start their transition due to the availability of residual heat. For rural municipalities, this will be more difficult due to a dependency on low-temperature systems. There, starting with the neighbourhoods that have the most potential to insulate is advised.

EPA: Multi-Modelling for Complex Challenges With the acknowledgement of international grand challenges, the demand for better and ever more complex models is likely to increase a manifold. Where single models may no longer be able to grasp the complexities of a system, multi-modelling (Nikolic, Warnier, et al., 2019; Vangheluwe, 2000) enables the combination of the strengths of different models whilst enabling the development of multi-perspective insights. In this research, I developed a multi-model to provide policymakers in The Netherlands with insights on how to steer the Urban Energy Transition at both national and municipal level. This is done by combining a System Dynamics (Forrester, 1961) model for evaluating market behaviour at the national scale, and an Agent-Based Model (Epstein & Axtell, 1996) for investigating investment behaviour at the neighbourhood level. The results from experiments with this model show that multi-perspective insights can be very helpful in designing policies and strategies for dealing with Sustainable Urban Development. It is found that challenges concerning the conceptualisation phase of the Model Development Cycle, could turn out to be opportunities for model development. As formalism selection and possible overlapping scales between models requires extra effort and attention, this attention results in model concepts that will be better evaluated, resulting in better concepts to be developed altogether. The main challenge that is currently unresolved, is that of the computational performance of multi-models. Although worsened by the choice for Agent-Based Modelling as one of the formalisms used in the multi-model, the computational requirements for the simulation seriously hamper the opportunities for experimentation and analysis. Although solutions can be found to minimise the computational demand or the effects of it, improvements are required in either computational demand or processing supply, for multi-models to become a suitable method for common modelling and simulation practice. CME: Energy Transition in the Built Environment With the EU goals (European Commission, 2018b) to reduce CO2 emissions to zero tons in 2050, The Netherlands has set up a climate agreement (Klimaatakkoord, 2019) in which municipalities get a leading role in reducing the carbon footprint of the Built Environment. To realise these goals, an energy transition is inevitable and strategies need to be developed for remodelling neighbourhoods into sustainable living environments. Before the end of 2021, municipalities have to come up with a plan in which they decide what neighbourhoods will be transformed and when. A problem in this is that currently, municipalities do not have the resources and tools to do so (RTL, 2019; Schuttenhelm, 2020; Straver, 2019). Currently, existing models, such as the Vesta MAIS model (Planbureau voor de Leefomgeving, 2019c) offered by the national government, are missing two crucial aspects which should help municipalities to set up their strategies: time dynamics and population dynamics. The techno-economic approach does present the ’best’ solution but is missing how to get there. Next to this, uncertainty around national policies makes that it is very difficult to decide on a robust policy. To deal with the aforementioned challenges, I use a multi-modelling approach (Nikolic, Warnier, et al., 2019; Vangheluwe, 2000), using System Dynamics (Forrester, 1961) and Agent-Based modelling (Epstein & Axtell, 1996) in which on the one hand, the time dynamics and population dynamics aspects are incorporated, and on the other hand multi-perspective insights on effects of national policies on national goals as well as insights on the heterogeneous effects at the municipal level are provided. An important finding is the crucial role of a CO2 tax on the realisation of national goals. Without this tax, homeowners and housing corporations will not be motivated sufficiently to significantly invest in insulation measures, making that fewer alternative heating systems will be implemented. Next to this, it is found that major differences can be distinguished between rural and urban areas. Heating grids will be a viable starting point for urban municipalities to start their transition due to the availability of residual heat. For rural municipalities, this will be more difficult due to a dependency on low-temperature systems. There, starting with the neighbourhoods that have the most potential to insulate is advised.