Can thermal retrofit measures also enhance summer heat resilience and climate justice? Two common building types of multifamily dwellings in Central Europe are investigated: the 'Gründerzeithaus' and postwar large-panel construction along with their different inhabitant demographics. Thermal simulations and demographic surveys were undertaken for dwellings in both building types to evaluate the effectiveness of retrofit measures in reducing winter heat demand and to understand the impacts on summer overheating. Results indicate that standard retrofitting measures can reduce the overheating risks. The high summer temperatures on the top floor can be significantly lowered to values comparable with the ground floor. The remaining overheating in highly exposed rooms is reduced by additional selective adaptation measures. Adaptation requires more than technical interventions. Demographic surveys conducted for both building types show that different social groups are affected. The economics of retrofit requires policy clarity to avoid placing additional burdens on economically disadvantaged people. Inhabitants' active involvement in night-time ventilation are vital for avoiding overheating. Appropriate affordances and a clear guidance for manual window opening/closing can reduce overheating. However, inhabitants who are unable to act (e.g. the elderly, immobile or those with chronic diseases) will be increasingly vulnerable and disadvantaged by increased exposure to overheating. Practice relevance The existing approaches for reducing heating demand and their impacts on overheating are examined for two common building types in Central Europe: the Gründerzeithaus and postwar large-panel multifamily housing. The evidence of physical effects and social interdependencies provides a basis both for decision-makers to select suitable measures, and for inhabitants to apply appropriate behavioural practices. Thermal retrofitting strategies for reducing winter heating demand can lead to enhanced resilience to hot summer weather, but also entail inhabitants' active involvement. Additional technical measures are needed to ensure reduced levels of overheating. Inhabitants' practices have a significant influence on resilience and the reduction of overheating. Therefore, technical interventions must be accompanied by clear strategies to empower inhabitants to control internal temperatures using natural ventilation. Elderly or ill inhabitants may not be able to perform these practices and, therefore, remain vulnerable. Increased rents caused by retrofits may displace socially disadvantaged inhabitants.

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Can building performance simulation reproduce measured summertime indoor conditions of a multi-residential building in good conformity? This question is answered by calibrating simulated to monitored room temperatures of several rooms of a multi-residential building for an entire summer in two process steps. First, we did a calibration for several days without the residents being present to validate the building physics of the 3D simulation model. Second, the simulations were calibrated for the entire summer period, including the residents’ impact on evolving room temperature and overheating. As a result, a high degree of conformity between simulation and measurement could be achieved for all monitored rooms. The credibility of our results was secured by a detailed sensitivity analysis under varying meteorological conditions, shading situations, and window ventilation or room use in the simulation model. For top floor dwellings, a high overheating intensity was evoked by a combination of insufficient use of night-time window ventilation and non-heat-adapted residential behavior in combination with high solar gains and low heat storage capacities. Finally, the overall findings were merged into a process guideline to describe how a step-by-step calibration of residential building simulation models can be done. This guideline is intended to be a starting point for future discussions about the validity of the simplified boundary conditions which are often used in present-day standard overheating assessment.

A major concern in climate adaptation is to enhance the heat resilient design of residential buildings. However, recent scientific literature addressing overheating analysis is only focussing on individual countries. In this article, we discuss how different design of representative apartment buildings in two countries influences the overheating risk or cooling demand and what conclusions can be drawn from it. This is done for a low-rise apartment building located in Germany and a high-rise building in South Korea applying building performance simulation. Both countries are located in the moderate climate zone, but regional differences in frequency of tropical nights and radiant summer days lead to significant differences in overheating intensity (800 Kh/a for the German and 5100 Kh/a for the Korean) or cooling demand (1800 kWh for the German to 1300 kWh for the Korean). The lower cooling demand but much higher overheating intensity of the Korean building compared to the German is mainly caused by the different solar heat gain due to the glazed balcony design of the Korean building where these balcony rooms are not actively cooled. On the contrary, the common internal façade insulation of Korean buildings results in a higher overheating risk compared to the German building and in addition the lower potential of passive cooling by natural ventilation due to the necessity of insect screens in Korea. The large effect of implementing heat adaptation measures on overheating risk reduction or cooling demand (up to 90%) clearly demonstrates that both buildings are far away from a heat resilient design and that heat adaptation measures can address both climate change adaptation and mitigation.

Durch die projizierte globale Erwärmung werden sich Hitzeextreme verschärfen. Vor allem in den Städten wird die Lebensqualität der Stadtbevölkerung unter sommerlichen Hitzewellen leiden. Im Projekt HeatResilientCity werden bewohnerorientierte Hitzeanpassungsmaßnahmen an Gebäuden und im städtischen Freiraum entwickelt und geprüft sowie Empfehlungen für die Umsetzung gegeben.The HeatResilientCity project applied insights from natural sciences, engineering and the social sciences to develop heat adaptation measures, test their effectiveness and partially implement them in two structurally different real-world laboratories in Dresden-Gorbitz and Erfurt-Oststadt. The present article discusses interventions to plant street trees and to refurbish two different residential buildings. We describe and analyse aspects of the implementation process to identify key factors that enable or constrain adaptation action among different groups of actors. We find that adaptation measures that are objectively effective and supported by residents are most appropriate for implementation. Where residents evince scepticism about adaptation measures, information about their effectiveness and usefulness should be disseminated. Early and targeted involvement of relevant stakeholders, careful communication and the establishment of climate adaptation as a permanent interdepartmental task at municipal level can promote successful implementation of heat adaptation measures.