Field measurements on lower radiator temperatures in existing buildings : manuscript for Energy and Buildings

The heating power of a building is linked to the supply and return temperature of the radiator. A lower supply temperature enables more transition pathways towards sustainable heating with reduced carbon emissions. However, the minimum supply temperature that guarantees thermal comfort during design weather conditions is still unknown. In this study, the minimum supply temperature is determined by fitting a 2R-2C model to high-frequency measurement data from a representative set of 220 existing dwellings in the Netherlands, followed by a novel fully data-driven determination of the minimum supply temperature. The heating system in each dwelling was equipped with a pulse flowmeter and temperature sensors on both the supply and return side of the radiator system. Additionally, we collected data from the thermostat in the main living room and the gas boiler. The data was supplemented with weather data from a nearby weather station. The data-driven model shows that the minimum supply temperature can be lower than 55 °C for 60% of the dwellings during design weather conditions. Moreover, the minimum supply temperature is poorly correlated with the building typology, construction period or specific annual space heating demand (kWh/m2). On the contrary, the ratio between the required and installed capacity of the radiator system proves a promising parameter to define the minimum supply temperature that guarantees a comfortable indoor temperature during design weather conditions.