The residential built environment in the Netherlands is on the verge of a transition of its thermal system. The Climate Agreement has suggested that municipalities will have to play a leading role in transitioning their neighborhoods' currently natural gas-driven heating systems towards sustainable alternatives. But changing the thermal systems of these neighborhoods will have consequences for the gas transmission system operator: Gasunie. Currently, no model captures this transition from the perspective of municipalities as key instigators while studying its implications on a transmission system operator. Therefore, this thesis presents a data-driven agent-based model representing the Dutch built environment consisting of municipalities, neighborhoods and energy sources to study the effect of municipal decisions in this transition on Gasunie's infrastructure. A novel municipal decision-making framework is designed that hypothesizes various factors contributing to municipal decisions in this transition. Aggregating peak gas demand to the level of Metering and Regulation stations in Gasunie's network captures the emergent behavior of interest from an infrastructural point of view. Simulation results show that the decisions of municipalities matter for the regionally required capacity in Gasunie's infrastructure, depending on the regional built environment characteristics, national transition goal, unfolding scenario, and municipal strategies. But the limited availability of renewable gas is a significant model driver and limits municipalities in what they can decide. It can be concluded that insight in the supply-side availability of the renewable gasses for the built environment in combination with multi-stakeholder coordination with the national policymaker and municipalities on the thermal transition can contribute to unraveling the uncertain character of this system and its implications for Gasunie's infrastructure. The agent-based model can expose the formulated theory of municipal decision-making and its effect on Gasunie's infrastructure while exploring and discovering what-if scenarios of interest for Gasunie and other stakeholders. It can potentially be used as a decision-support or debate starting tool by the involved stakeholders to show how their interests, characteristics, and decisions shape the change of this thermal system towards its sustainable future.