Analysing the evolution of thermal energy demand of buildings based on different scenarios is essential for assessing the effectiveness of national energy policies. This study applies a bottom-up archetype model in combination with a dynamic building simulation model to calculate the heating and cooling demand of Swiss residential and non-residential buildings based on different climate and retrofit scenarios. The results show a substantial reduction in space heat demand in 2050 (Multi-Family Houses MFHs: 32–48%, Single-Family Houses SFHs: 44–56%, Offices: 23–32%, Schools: 21–31%). Assuming climate scenario RCP 2.6 and an advanced retrofit scenario (annual deep retrofit rate = 1.5%, assumed to be fully effective, predominantly with renewable heating), final energy consumption for residential space heating is expected to reach 21.7 TWh/year in 2050, compared to 39.9 TWh/year in 2023. This demonstrates that retrofit policies and the adoption of more efficient heating systems will substantially reduce heat consumption but will not be sufficient to achieve the reduction targets according to the national energy plan (18 TWh/year by 2050). Among the various factors influencing these savings, the switch to more efficient heating systems is most effective (−36.8%), followed by building envelope retrofit (–23.7%) and the effects of climate change (−6.0%). Assuming different adoption levels for cooling (10%-45%), the related electricity demand will increase substantially, considering population growth and rising average temperatures (MFH: +134–250%, SFH: +135–294%, Offices: +7–35%, Schools: +100–200%). Building envelope retrofit leads to a substantial reduction in specific heat demand for all types of buildings, with an average of 57% for residential buildings, but at the same time leads to an increase in specific cooling needs (average 5.8 kWh/m²/year).