## 3 Methodology
Clear low-e glazing was found to provide the best performance in Hong Kong according to [PERSON]'s study (2018). Both \"LoE 6 mm\" and \"LoE Spec Sel 6 mm\" are two types of clear double plane fenestration systems with low-e coating. Figure 1: Typical floor layout and modelled thermal zones. \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Type**} & \multirow{2}{*}{**U-Value (W/m\({}^{2}\)-K)**} & \multirow{2}{*}{**Solar Heat Gain Coefficient (SHGC)**} & \multirow{2}{*}{**Visible Tranmittance (VT)**} \\ \hline Clear 6 mm & 5.8 & 0.82 & 0.88 \\ LoE 6 mm, & 3.4 & 0.64 & 0.84 \\ LoE Spec Sel 6 mm & 3.2 & 0.47 & 0.77 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: General construction and building material data. Figure 2: Building operation schedules. All floors in this building with boundary conditions can be categorized into three different types of floor, i.e., ground (G), typical (TYP), and top (TOP). The G floor is the floor directly contacting the ground surface. The TOP floor is that with a rooftop which is directly exposed to the sun and wind. The TYP floor is the floors among these two floors. For this study, the context is not modelled and simulated. Suggested by an initial test, the performance difference between floors should mostly be incurred by different boundary conditions. The floors between TOP and G have identical geometry and boundary conditions thus can be generally represented by a TYP floor in the middle of the building. This sandwich modelling method may reduce some accuracy, but it significantly reduces the computational complexity as well as the simulation time for this 40-floor building. Modeling the three types of floors and adding multipliers can generate a similar result to the actual building consumption. Thus, the alternative modeling approach is used, and the simulation model is as shown in Figure 3. Two intermediate floors are added between these floors to offset the inter-influence of types of floor models when directly placed adjacent to each other. A multiplier at 36 is added to the typical floor to calculate the energy consumption of the whole building. \begin{table}
\begin{tabular}{c c} \hline \hline
**Name** & **SavE OM29 \({}^{*}\)** \\ \hline Thickness (mm) & 5 \\ Density (kg/m\({}^{3}\)) & 1830 \\ Specific Heat (J/kgK) & 2300 \\ Melting Temperature (\({}^{\circ}\)C) & 29 \\  & at 26 \({}^{\circ}\)C & 8 \\  & at 27 \({}^{\circ}\)C & 36 \\ Enthalpy for 1 \({}^{\circ}\)C change near & at 28 \({}^{\circ}\)C & 30 \\ melting temperature (kJ/kg) & at 29 \({}^{\circ}\)C & 61 \\  & at 30 \({}^{\circ}\)C & 29 \\  & at 31 \({}^{\circ}\)C & 15 \\ \hline \hline \end{tabular} \({}^{*}\) SavE OM29 was the only product found online to have a high-phase change temperature at 29 \({}^{\circ}\)C and detailed data of its characteristics.  
\end{table} 
Table 3: Material properties of PCM. Figure 3: The sandwiched EnergyPlus Simulation Building Model. Note: top floor (TOP), ground floor (G) and typical floor (TYP). TOP—zone roofs and exterior walls exposed to outdoor condition; G—zone floors in contact with the earth, exterior walls to outdoor; TYP—zone exterior walls exposed to outdoor condition. Intermediate floors—the buffer zone between TOP and TYP as well as G and TYP to limit the heat flows and increase TYP floor accuracy. In Hong Kong, the common type of HVAC system in residential buildings is the window type unitary unit. Thus, the \"unitary system\" is applied in this model. The model is calibrated and validated based on its cooling load and zone air temperature, and is compared to the local benchmark to ensure the accuracy of the simulation result. Buildings' HVAC systems are turned off completely from 1 November to 31 March in accordance with the cooling period in Hong Kong. The simulation of other components is achieved by specifying the specific inputs in EnergyPlus. The HVAC system coefficient of performance (COP) is at 3 for cooling. As heating is not provided in Hong Kong, heating power is set to 0, i.e., no heating.