## 2 Model Setup and Validation  
### Computational Domain  
In the present study, a room located at the middle of an intermediate floor is selected as the model prototype, as shown in Figure 1. The room's internal dimensions are 4 m (length) \(\times\) 4.3 m (width) \(\times\) 2.7 m (height) and the floor area is 17.2 m\({}^{2}\). The insulated external wall consists of 0.2 m reinforced concrete layer and 0.035 m extruded polystyrene (XPS) layer inside of the reinforced concrete layer. A single-glazing window in the external wall has dimensions of 2.5 m \(\times\) 1.2 m. The ceiling and floor are made of a 0.1 m reinforced concrete layer. Moreover, all the walls are plastered on both sides with 0.015 m cement layer. Two pieces of furniture, with the sizes of 2.2 m \(\times\) 0.8 m \(\times\) 0.3 m + 0.6 m \(\times\) 0.6 m \(\times\) 0.3 m (L \(\times\) W \(\times\) H, furniture 1) and 1.6 m \(\times\) 0.55 m \(\times\) 0.3 m (L \(\times\) W \(\times\) H, furniture 2), respectively, are placed inside the room. The warm air inlet, with dimensions of 0.7 m \(\times\) 0.1 m, is at a height of 2 m from the floor level, while the air outlet, with the same dimensions, is 0.3 m above the air inlet. Four different configurations of internal walls commonly used in the HSCW zone are considered in this paper. A detailed schematic of internal wall configurations is shown in Figure 2. Figure 2a shows the Wall 1 containing thermal mass layer of 0.2 m reinforced concrete and 0.015 m plaster layers. Figure 2b shows the Wall 2, which consists of thermal mass layer of 0.2 m reinforced concrete, 0.03 m insulation layers of thermal mortar and 0.015 m plaster layers. Figure 2c shows a lightweight wall (Wall 3), which contains base wall layer of 0.2 m aerated concrete block and 0.015 m plaster layers. Figure 2d shows the Wall 4 containing thermal mass layer of 0.2 m reinforced concrete, insulation layers of 0.02 m XPS board and 0.015 m plaster layers. Thermal properties of the construction materials are given in Table 1.  
The thermal resistance and thermal diffusivity of the four walls are also given in Table 2 to better understand the heat conduction and storage process of walls. Due to the effect of the thermal bridge, the heat transfer of connections between external and internal walls as well as the floor is a three-dimensional unsteady process. The heat transfer through \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Material** & \begin{tabular}{c} **Density \(\rho\)** \\ **(kg/m\({}^{3}\))** \\ \end{tabular} & \begin{tabular}{c} **Specific Heat Capacity \(c\)** \\ **[/kg\({}^{-}\)C]** \\ \end{tabular} & \begin{tabular}{c} **Thermal Conductivity \(\lambda\)** \\ **[/m\({}^{-}\)C]** \\ \end{tabular} & \begin{tabular}{c} **Thermal Storage \(\xi\)** \\ **[/m\({}^{2}\)/s]** \\ \end{tabular} \\ \hline \hline \begin{tabular}{c} Plaster layer \\ Reinforced concrete \\ Thermal mortar \\ Aerated concrete block \\ XPS \\ \end{tabular} & \begin{tabular}{c} 1700 \\ 2500 \\ 600 \\ 700 \\ 35 \\ \end{tabular} & \begin{tabular}{c} 1050 \\ 920 \\ 1050 \\ 1380 \\ \end{tabular} & \begin{tabular}{c} 0.87 \\ 174 \\ 174 \\ 0.18 \\ 0.18 \\ 0.036 \\ \end{tabular} & \
\begin{tabular}{c} 10.75 \\ 172 \\ 2.87 \\ 2.45 \\ 0.32 \\ \end{tabular} &
\begin{tabular}{c} 4.87 \\ 7.57 \\ 2.86 \\ 2.45 \\ 0.45 \\ \end{tabular} \(\times\)\(10^{-7}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Thermo-physical properties of building construction materials [5]. Figure 1: Schematic of the room: (**a**) three-dimensional schematic of the room model; (**b**) side view (plane _y-z_) of the model. Figure 2: Sections of four kinds of internal wall structures. the external wall is considered to be one-dimensional along the \(x\)-axis away from the connectors. For this reason, the envelopes of 0.5 m height in the four adjoining rooms on the directions of \(\pm y\), \(\pm z\) based on the investigated room are also contained in the computational domain (seen in Figure 1). Moreover, the cross-sectional planes of envelope in the adjoining rooms are adiabatic surfaces.