Study on energy-saving potential of lowering the emissivity of unheated surfaces for floor radiant heating

Abstract

It has been demonstrated that the application of low emissivity materials to unheated surfaces improves the thermal comfort level of radiant heating. However, it remains unclear whether the emissivity of unheated surfaces can shorten the response time of floor radiant heating (FRH) and whether there is energy-saving potential. Numerical simulations were conducted to determine the influence of unheated surface emissivity and wall insulation methods on the dynamic performance of FRH during intermittent operation. The results indicate that decreasing the emissivity of the unheated surface can effectively shorten the response time of FRH by 26.8 %, but at the expense of an increased start-up load. The difference between start-up load and steady heating load is between 1.8 and 2.3 times, which increases with the area of the internal insulating wall. Two energy-saving measures exhibit a "substitution" relationship that must be combined with an economic analysis to determine a reasonable implementation scheme, with the roof occupying a key position. This study provides an alternative energy-saving solution for heating and air conditioning in the hot summer and cold winter zone of China, as well as a design foundation for the promotion and application of FRH.