## 3 Case-Study Building and Retrofit
### Building Envelope  
The current envelope of the case-study building consists of a concrete plaster and autoclaved aerated concrete, which is easier to build during the construction period. Its cost is lower than that of new materials. However, its thermal properties are not suitable and can cause a thermal impact on energy usage in air conditioning systems. Thus, an insulator will be added to this component to improve the thermal properties in the envelope section without significant changes to the base component. The thermal properties of all materials used in the current building envelope are summarized in Table 6.  
The composition of the building wall consists of autoclaved aerated concrete and cement with a dark color for the exterior. The retrofit was performed by installing an insulator and gypsum board with a small air gap to increase the heat resistance of the wall section. This can be easily done and does not require removing the old building skin. The material and composition of both the current and newly retrofitted envelopes, including thermal transmittance (U-Value), are reported in Table 7.  
The material and composition of the current rooftop consist of steel-reinforced concrete with an air gap as an insulator and gypsum board. In the case of retrofitting, only a one-inch thermal insulator was installed over the gypsum board to avoid weight burden on the ceiling holder. A simplified diagram of the components of the roof material, details of the material in the component, and thermal properties are listed in Table 8.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Material** & \begin{tabular}{c} **Thermal Conductivity** \\ **(W/mK)** \\ \end{tabular} & \
\begin{tabular}{c} **Density** \\ **(kg/m3)** \\ \end{tabular} &
\begin{tabular}{c} **Specific Heat** \\ **(kJ/kgK)** \\ \end{tabular} \\ \hline Concrete plaster & 0.72 & 1860 & 0.84 \\ Autoclaved Aerated Concrete & 0.476 & 1280 & 0.84 \\ Gypsum plates & 0.282 & 800 & 1.09 \\ Fiberglass insulation & 0.033 & 32 & 0.96 \\ Reinforced concrete & 1.442 & 2400 & 0.92 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Thermal properties of opaque materials employed in the envelope of the case-study building.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Composition** & **Detail** & **Thickness (m)** & **U-Value (W/m2K)** \\ \hline \hline \multirow{4}{*}{Base case} & Concrete plaster & 0.010 & \\  & Autoclaved Aerated Concrete & 0.200 & 1.634 \\ Concrete plaster & 0.010 & \\ \hline \multirow{4}{*}{Retrofitted case} & Gypsum plates & 0.015 & \\  & Fiberglass insulation & 0.100 & \\ \cline{1-1}  & Air Gap & 0.100 & 0.396 \\ \cline{1-1}  & Autoclaved Aerated Concrete & 0.200 & \\ \cline{1-1}  & Concrete plaster & 0.010 & \\ \hline \hline \end{tabular}
\end{table}
Table 7: Composition of opaque materials employed for the wall of the case-study building. U-value: thermal transmittance.  
The transparent section of the building is only composed of windows with 6 mm clear glass. The retrofitted window is a double-pane type with the inner side made of ocean-green float glass and the outer side made of clear float glass with a low-e coating. The composition of these two types of windows and their thermal properties are summarized in Table 9.