## 4 EnergyPlus Simulation Results
### Analysis of Energy Saving Rate in Different Climate Zones
In this cold weather, the heating energy saving is high, and showed the highest saving rate of 19.6%. Glazing with better insulation performance  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & & \multicolumn{2}{c}{**Incheon**} & \multicolumn{2}{c}{**Minneapolis**} \\ \cline{3-6}  
minimized heat transfer. This resulted in saving heating energy and increasing thermal comfort for the occupants. When the glazing U-value and investment cost in various climates were analyzed, a glazing system with optimized insulation was more suitable in cold climates than in hot and humid climates [48; 49]. According to the results from applying the CAV + GSHP, the energy saving rate was 8.1% (39.3 \(-\) 31.2%) more in Minneapolis than in Incheon. In Minneapolis, heating energy showed the highest saving of 52.5%. The ground source heat pump (GSHP) is a highly efficient technology for heating in cold regions [50]. A related study also showed the minimum and maximum values of COP during the heating season were higher in the GSHP than those of the air source heat pump (ASHP). The GSHP provides a COP that is up to three times higher than that of the ASHP [51]. The ASHP becomes less efficient in the heating season due to the low outdoor air temperature. Applying high-performance GSHP systems is more effective in cool and cold climates compared to conventional heating systems [52]. The energy saving rate of the VAV + economizer was 8.8% (42.9 \(-\) 37.1%) more in Minneapolis than in Incheon, due to the appropriate outdoor air cooling in the intermediate season. The cooling energy (45.9%) and fan energy (69.9%) savings were particularly high. The outdoor air intake using an economizer is inefficient in hot-humid climates and the cooling season of mixed climates. When applying an economizer in cool and cold climates, outdoor air temperature control or enthalpy control can also be used. The energy saving rate of the ERV in Minneapolis was 12.1% (45.4 \(-\) 39.3%) more than that in Incheon. This was due to the heat recovery from the low outdoor air temperature in the heating season. The heating energy (49.1%) and fan energy (60.8%) savings were particularly high. When the VAV + ERV is applied to office buildings, the efficiency of the operation of the ERV can be increased by controlling the VAV system damper. The VAV + ERV system typically shows high heating energy saving rates in cool and cold regions [53]. When the active chilled beam with DOAS was applied in Minneapolis, its energy saving rate was 8.1% (55.7 \(-\) 47.6%) more than that applied in Incheon. Specifically, the heating energy (67.8%) and fan energy (68.9%) saving rates were high. When the DOAS is applied in various climates, the energy efficiency is lower in hot and humid regions [54; 55]. Hot and humid outdoor heat is exchanged with cold and dry exhaust air in hot climates, which increases the cooling coil energy consumption. However, because the system can utilize relatively cool outdoor air in cool and cold climates, and due to the heat recovery from the exhaust air, the DOAS can save a large proportion of the heating and dehumidification load in cool and cold climates [56]. The details of energy saving rates when the high-performance technologies are applied to Berlin (Cool humid zone_5A) in comparison with the Incheon climate (Mixed zone_4A) are shown in Table 11. Based on previous research and simulation results, the effective technologies in each climate zone are summarized in Table 12.