## 2 Methodology
### Simulation Modeling  
#### 2.2.1 Baseline Model  
This study modeled a virtual office building using EnergyPlus Ver 9.3 [29]. Figure 3 shows the building envelope and the schematic of the HVAC system, which was modeled based on the DOE-2 reference model [30]. The building's volume is 1350 m\({}^{3}\) (30 m \(\times\) 15 m \(\times\) 3 m). The window-to-wall ratio (WWR) on the north and south sides is approximately 0.4, while on the east and west sides, it is approximately 0.5. Table 2 lists the input values used for the simulation modeling. The indoor cooling set-point was established at 24 \({}^{\circ}\)C. Internal heat generation factors from occupants, lighting, and equipment were set at 120 W/person, 6.89 W/m\({}^{2}\), and 6.78 W/m\({}^{2}\), respectively, adhering to the guidelines for small offices in ASHRAE Standard 90.1. The HVAC system, a variable-air-volume (VAV) type, controls the air flow to each room. The applied economizer  
Figure 2: Flow chart of overall research methodology.  
control utilized a fixed method based on dry-bulb temperature [31]. The maximum and minimum OA intake rates were set at 100% and 30%, respectively. The operating hours for the cooling system were scheduled from 7:00 to 18:00 on weekdays as per the Building Energy Efficiency Certification [32]. Cooling system components included an air-cooled chiller, a chilled water coil pump, and a variable-speed fan, with capacities calculated using the autosize function in EnergyPlus, resulting in 19,240 W for the chiller, 292 W for the pump, and 0.4 m\({}^{3}\)/s for the fan [33]. As the majority of regions in South Korea fall within the 4A climate zone, this study utilized weather data from Daejeon, South Korea, a representative city in this climate classification. Weather data for the simulations were sourced from the international weather files for energy calculation 2.0 (IWEC2) for Daejeon [34]. Economizer control is inactive during winter and summer due to excessively low or high OA temperatures. Therefore, the simulation period was set to the interseason (i.e., Mar., Apr., May, Oct., and Nov.), when economizer control is active. Simulations were conducted at 1 min intervals.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Input Parameters** & **Values** & **Information Source** \\ \hline \multirow{8}{*}{Building} & \multirow{8}{*}{Zone} & Use & Office building \\ \cline{3-4}  & & Floor area & 450 m\({}^{2}\) \\ \cline{3-4}  & & Floor-to-floor height & 3 m \\ \cline{3-4}  & & WWR & North and south & 0.4 \\ \cline{3-4}  & & East and west & 0.5 \\ \cline{3-4}  & & Indoor cooling set-point & 24\({}^{\circ}\)C \\ \cline{3-4}  & & People & 120 W/person \\ \cline{3-4}  & & Light & 6.89 W/m\({}^{2}\) \\ \cline{3-4}  & & Equipment & 6.78 W/m\({}^{2}\) \\ \hline \multirow{8}{*}{System} & \multirow{8}{*}{Operation} & HVAC & VAV \\ \cline{3-4}  & & Economizer control type & Dry-bulb temperature \\ \cline{3-4}  & & Maximum OA intake rates & 100\% \\ \cline{3-4}  & & Minimum OA intake rates & 30\% \\ \cline{3-4}  & & Supply air dry-bulb temperature & 13\({}^{\circ}\)C \\ \cline{3-4}  & & Supply air absolute humidity & 0.008 kg/kg\({}^{\prime}\) & 90.1-2019 \\ \cline{3-4}  & & Weekdays & 07:00–18:00 & Building Energy \\ \cline{3-4}  & & Weekends & None & Efficiency Certification \\ \hline \hline \end{tabular}
\end{table}
Table 2: Summary of input values used for simulation modeling.  
Figure 3: Schematic of simulation baseline model: (**a**) 3D view of simulation building envelope; (**b**) simplified simulation HVAC system.