Due to desirable emission reductions and population growth, increasing energy demand is identified as a dire issue for energy systems. The introduction of low-energy building districts enables increased energy system efficiency. This study’s aim is twofold. Firstly, an extensive urban building energy model is used to simulate the hourly use and geographic distribution of the heat demand for residential and commercial buildings that are to be supplied by a low-temperature district heating system. The simulated buildings are a part of a planned city district, located in Gävle, Sweden. Two building energy performance cases are studied; one where all buildings are assumed to be of Passive House standard, and one where the building energy performance is in line with conventional new-building regulations in Sweden. Secondly, one specific building is modeled in detail and simulated in the building energy simulation software IDA ICE to investigate what building heating system is best suited for low-temperature heat supply. The temperature demands of floor heating and ventilation with heat recovery are investigated and compared to conventional water-based radiators. The building’s temperature demand results can be used when designing a lowtempered district heating system which will provide the supply temperature to identify a compatible heating system technique. Varying supply temperature demand will enable optimization for choosing building heating systems and consequently, possible cost reductions. The results could be used as an example for future city district planning as well as presenting relevant heating systems for low-temperature district heating.