Future climate resilience of energy-efficient retrofit projects in central Europe

Sammanfattning: This study assesses the performance of buildings affected by climate change under future climate predictions for three time-periods until the end of the 21st century. Objects studied are residential multi-storey buildings, originally built before 1970 and retrofitted during the last decade. A total of four actual retrofit projects, as they were performed, in Denmark and Germany were assessed in their initial and retrofitted stage. The investigation assessed indoor thermal comfort, heating energy demand, heating peak loads by means of building performance simulations. Further, hygrothermal simulations were used to test the performance of constructions in the thermal building envelope. Climate data sets employed composed of a set of nine weather files per location, accounting for non-extreme and extreme cold and warm conditions divided into 30-year periods. The results show for all retrofitting measures a decrease of energy consumed for space heating. Due to the improved building airtightness and thermal conductivity of the building envelope constructions, sizing of heating systems and terminal devices was minimised accordingly. Similar paradigms show for periods closer to the end of the century, as the annual heating energy demand decreases gradually. An increase in summer thermal discomfort towards the end of the century was observed in all study objects, especially during extreme hot summer-periods thermal discomfort is ubiquitous. The German case studies showed that passive measures to decrease local discomfort are insufficient during extreme periods with increasing thermal discomfort towards the end of the century. The realisation of highly insulated thermal envelopes yielded immense overheating issues for the German future climate predictions. The majority of initial thermal envelope constructions showed vulnerabilities for moisture related issues within future climate scenarios. Most retrofitted elements are predicted to withstand climate change without high risk for mould growth. This mainly bases on the material selection which is crucial along with a thorough hygrothermal assessment for ensuring a resilient building design under the uncertainties of future climate.