## 5 Conclusions  
Energy retrofit of historic building in South Tyrol focuses mainly on reducing the heating demand due to the perception of the local climate as \"cold\". However, the analysis of historical and future trends of extreme heat events reveals the increasing challenges that a warming climate will bring in ensuring thermal comfort. Energy use and thermal comfort conditions in two characteristic Alpine residential buildings are compared under a wide range of climate projections for the periods of 2008-2018, 2041-2050, and 2091-2100. The results of this investigation increase the understanding of climate change implications for energy retrofitted historic buildings under different climate assumptions. Several factors influencing the definition and severity of indoor overheating risk are analysed including assessment methods, climate change, energy retrofit measures, and building characteristics. It is found that (i) overheating risks exist in both retrofitted Portici houses, independent of the assessment method used. However, there are important discrepancies in the extent of such overheating risk as the assessment method with fixed operative temperature threshold (CIBSE guide A) predicts higher overheating ratio than the adaptive assessment method (EN15251). It is thus important to further study the representativeness of both methods and provide clear guidance for practitioners and policy makers in this matter. (ii) Current practices of energy retrofit of historic buildings could achieve significant savings in the energy use for space heating, even in the case of future warmer climate. However, it will introduce substantial risks of overheating in the future (\(\Delta\)3 in Table 8), which must be carefully considered. Since buildings built before 1945 comprise 22% of the total residential stock of South Tyrol [35], it is sensible to adopt energy retrofit to mitigate climate change. Effective overheating control practices should be identified to achieve energy efficient and thermal comfort at the same time. (iii) Surface-to-volume ratio, shading and air exchange ratio are critical factors in overheating risks. Focusing on shading and ventilation as adaptation strategies will allow the implementation of energy efficient renovations for historic buildings while at the same time ensuring the thermal comfort of their occupants, and with that prevent the risk of increased energy use for cooling in the warmer months of the year. With the future climate trends, overheating risks and influencing factors addressed in the retrofitted historic buildings of Alpine region, this study shows that with proper adaptative solutions, the counter effect of energy retrofit and global warming in overheating could be controlled and thereby optimised historic buildings' performance. It is suggested that current energy retrofits should adopt a wholistic approach and include adaptation measures (such as shading and ventilation) as part of the interventions. Impact assessment of climate change and energy retrofit are important to achieve an efficient and comfort historic building. However, interesting discrepancies were found in two reference buildings. Retrofitted historic building of Climate zone I showed more climate-flexibility (fewer overheating hours increases facing climate change) compared with un-retrofitted one while the other reference building presented the opposite result. Comparable reference buildings and climate scenarios need to be defined and further investigated. Moreover, insufficient empirical data and relevant local guidelines on heating and occupancy profile were found where future work needs to be conducted. Conceptualization, L.H. and D.H.-A. ; methodology, L.H. and D.H.-A. ; writing--original draft preparation, L.H. ; writing--review and editing, D.H.-A., C.D.P. and A.T.; supervision, A.T. and C.D.P. All authors have read and agreed to the published version of the manuscript. The APC was funded by Hebei Key Research Institute of Humanities and Social Sciences at Universities. Not applicable.