Heat losses of low-temperature radiant heating systems

Abstract

There is a consensus among stakeholders that nearly zero energy buildings (nzeb’s) represent a step forward towards low-carbon societies. The envelope of nzeb’s is well insulated, so there are cases when the external building elements are used as radiant heating surfaces (floor, ceiling, and walls). There is little information about the heat losses of the low-temperature radiant heating systems installed on the inner surface of the external opaque building elements. The purpose of this study was to quantify and compare the energy used for heating in the case of traditional radiator heating and three different radiant heating modes. The calculation methodology was validated by laboratory measurements. Three different thermal requirements related to the building envelope have been assumed and two different heat sources, so 24 different cases have been analyzed in detail and the energy used was compared. The switch-on and switch-off temperatures were determined using the heat gains utilization factor calculated on a daily basis. It was shown that the energy used for heating in the case of radiant heating (taking into account the delivered heat and the heat losses) exceeds the energy used in the case of radiator heating. In the case of nzeb’s the difference is the highest and may reach even 23.2%–24.8%.