Most apartment buildings in South Korea use internal insulation systems to reduce building energy demand. However, thermal bridges such as balcony slabs in apartment buildings still lead to significant heat loss in winter, because the internal insulation system is not continuous in the balcony slab structure, and floor heating systems are commonly used in residential buildings. Therefore, this study investigates two types of thermal break elements, namely thermal break (TB) and thermal break-fiber glass reinforced polymer (TB-GFRP), to improve the thermal resistance of a balcony thermal bridge. To understand the effects of balcony thermal bridges with and without thermal break elements, the linear thermal transmittances of different balcony thermal bridges were analyzed using Physibel simulations. Then, the heating demand of a model apartment under varying thermal bridge conditions was evaluated using TRNSYS simulations. To understand the effect of insulation systems on heat loss through a balcony thermal bridge, apartments with internal and external insulation systems were studied. Whether the apartment was heating was also considered in the thermal transmittance analysis. Thus, the linear thermal transmittance of the thermal bridges with thermal break elements was reduced by more than 60%, and the heating energy demands were reduced by more than 8%.

Ground source heat pump (GSHP) can increase ground temperature and reduce system coefficient of performance (COP) during long term operation in the cooling season. This study proposed a GSHP cooling system combined with a hot water heat pump to improve the performance of the GSHP system. In the present study, the system was configured so that the condensation heat from GSHP could be used as the evaporative heat source for the hot water heat pump. This study analyzed the COP of the proposed combined system, a single cooling system and a single hot water system by TRNSYS 18 simulation. Simulation results showed that the COP of the proposed system was 37.27% higher in the cooling part and 14.40% higher in the hot water part, compared with the single heat pump system.