Overheating in buildings is predicted to increase as a result of a warming climate and urbanisation in most cities. It is a phenomenon with a significant concern in the context of energy use; and occupant's thermal comfort, productivity, health & well-being. With regards to responding to this challenge, decision makers ranging from_ design teams, local authorities, property developers, building users, building managers, national programs and market innovators; and during the different stages of a building’s service life, want to know a few pertinent matters, especially in the context of climate change and urbanization: What space characteristics and buildings are at a higher risk and by how much?; What are the tradeoffs between alternative design and/or user-based actions?; What are the likely or possible consequences of their decisions?; What is the impact of climate change to indoor overheating?; among other decision support questions. If answers to these questions can be identified, this could aid in deciding at particular moments of a space and/or buildings’ lifespan, preferences, as well as heat mitigating trade-off options. This paper addresses these issues by focusing its analysis on space and time-dependent patterns of overheating vulnerability with corresponding heat mitigation responses incurred in Nairobi's heterogeneous urban landscape; a landscape whose characteristics change with time, in an unpredictable world and in a warming climate. The study presents a method to assess the combination of thermal design and building use attributes to reduce the risk of indoor overheating in passively cooled spaces for a changing climate in Nairobi, Kenya. The method's potential has been demonstrated through its application to free-running office buildings in Nairobi, Kenya. Its supporting collection of techniques and tools for analysing indoor overheating risk processes in Nairobi, has aided in identifying and quantifying the effectiveness of coping, prevention and adaptation strategies to managing both short and long-term indoor overheating risk. Overall, both as an exploration of method and as an application to overheating management in Nairobi, this study draws attention to the potential of uncovering the dynamic complexity related to cause-effect-response interactions of variables that characterize the ‘thermal space'. This research demonstrates how the cities of the future can anticipate and mitigate overheating risk by re-envisioning the means of revealing, exploring and exploiting the 'overheating management space' in an integrated platform. From which certain inevitabilities, opportunities and possible threats, as well as common threads of trends in an overheating space can be drawn to inform temporal decision strategy.