Assessing future changes in heating and cooling degree days using multiple base temperatures for cultural heritage sites in Greece: A case study of Thessaloniki and Delphi

As the climate changes, accurate predictions of future energy demand are critical for residential buildings but particularly for cultural sites such as historical buildings and museums, to provide optimal environmental conditions for the preservation of cultural heritage and visitors' comfort. Future Heating Degree Days (HDD) and Cooling Degree Days (CDD) changes can provide valuable information for many sectors including museums which need to maintain stable indoor temperatures to protect their collections. In the present study, HDD and CDD are calculated for two Greek regions, Thessaloniki and Delphi, which host numerous museums and historical buildings providing useful information for future energy consumption. HDD were calculated for base temperatures of 15 °C, 16 °C, 17 °C and 18 °C, while CDD were computed for base temperatures of 23 °C, 24 °C, 25 °C, and 26 °C. The study was carried out for the reference period (1989-2000) and for two future periods (2039-2059 and 2079-2099). Daily simulated data were derived from the Regional Climate Model RegCM4 with a fine spatial resolution of 10 × 10 km. In addition, the emission scenario RCP4.5 was used for the model's future simulations. An increase in base temperature leads to higher estimates of CDD, whereas a decrease in base temperature increases HDD. Future projections indicate a decline in HDD and an increase in CDD, reflecting a shift in energy requirements in both case studies. The seasonal analysis revealed a substantial decrease in heating needs during winter and a notable increase in cooling demands during summer. Transitional months also show marked changes, indicating extended warm periods. Overall, the study highlights that in both regions the demand for heating is expected to decrease due to warmer temperatures, while energy requirements for cooling are anticipated to increase, indicating a shift in energy distribution from heating to cooling.