Denmark has a long-term objective of being free of fossil fuels by 2050, with the energy supply mix for buildings being fossil-free by 2035. Energy consumption for existing buildings needs to be decreased concurrent with the conversion from fossil-fuel supply to renewable-energy (RE) supply. When end-use savings are implemented in buildings concurrent with the application of low-temperature district heating (LTDH), the heat profiles of the buildings will change. Reducing peak loads is important, since this is the dimensioning foundation for future district heating systems. To avoid oversized RE-based capacity, a long-term perspective needs to be taken. Applying LTDH in existing buildings without changing the heating system implies reduced radiator performance, so it is of great importance that acceptable comfort temperatures can still be provided. The results indicate that it is possible to apply LTDH most of the year without compromising on thermal comfort if energy renovation is also implemented.