## 4 Retrofitted Results
### Investment Cost  
The evaluation of the economic feasibility using economic indexes for the retrofitting of existing building projects can be done by calculating the investment cost in comparison with the energy cost savings that can be achieved after retrofitting. Thus, the investment cost for retrofitted existing buildings reflects the cost of material and labour. An investment from government projects in term of material and labour cost must comply with the CGD, belonging to the Ministry of Finance [28]. Standardisation materials and labour cost must be considered; thus, it constitutes a reference for investment cost calculation. The investment cost for retrofitted building envelopes, including the material, labour, and electric equipment, is summarised in Table 17. Note that the material and labour costs for insulators are not expensive. However, the higher thermal efficiency glass for windows can result in an increased cost in the retrofitted building envelope.  
The equipment and installation costs for the lighting system is summarized in Table 18. The air condition system is summarized in Table 19, and the PV system is shown in Table 20. In the case of lighting systems, the equipment cost for LED replacement is low because of the cost of luminaires, which continuously decreases thanks to the constant development of technology. However, the installation cost is fixed, even for different types of luminaires. Concerning the air conditioning system, the installation cost is included in the cost of the air conditioning unit. Finally, regarding the renewable energy, the cost of PV panels and inverters was significantly reduced over the past decade. By contrast, the cost mainly includes the removal of the metal sheet roof on the roof top and the construction of the PV system structure.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Material Name** & **Cost Per Unit** & **Labour Cost Per Unit** & **Total Cost** \\  & **(USD/m2) * & **(USD/m2) * & **(USD/m2) * \\ \hline Autoclaved aerated concrete (20 cm.) & 12.47 & 2.60 & 15.07 \\ Concrete plaster & 4.00 & 2.67 & 6.67 \\ Reinforced concrete & 326.27 & 67.10 & 393.37 \\ Gypsum plates & 10.63 & 2.50 & 13.13 \\ Fiberglass insulator (5 mm.) & 8.33 & 0.83 & 9.16 \\ Fiberglass insulator (10 mm.) & 16.67 & 0.83 & 17.50 \\ Clear float glass & 6.45 & 0.37 & 6.82 \\ Clear color single silver low-e coat on ocean green & 56.00 & 4.00 & 60.00 \\ \hline \hline \end{tabular}  
* The exchange rate is 30 THB (Thai bath) per 1 USD.  
\end{table}
Table 17: Material and labor cost for retrofitted projects in the envelope section.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Luminaire** & **Quantity** & **Price Per Unit (USD)** & **Installation Cost Per Luminaire (USD)** & **Total Cost (USD)** \\ \hline LED Bulb 9 W & 1227 & 2.57 & 4.00 & 8057.30 \\ LED Blub 14 W & 8 & 21.5 & 4.00 & 204.00 \\ LED Blub 27 W & 189 & 31.23 & 4.00 & 6659.10 \\ LED Tube 9 W & 235 & 4.97 & 4.00 & 2107.17 \\ LED Tube 18 W & 403 & 5.53 & 4.00 & 3841.93 \\  & & Total & & 20,869.50 \\ \hline \hline \end{tabular}  
\end{table}
Table 18: Equipment and installation cost of lighting systems.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Type of Air Conditioning Unit** & **BTU/h** & **Quantity** & **Price Per Unit (USD)** & **Total Cost (USD)** \\ \hline Variable speed & 9000 & 38 & 573.33 & 21,786.67 \\ (Inverter) & 12,000 & 36 & 643.33 & 23,160.00 \\  & 18,000 & 42 & 863.33 & 36,260.00 \\  & Total & & & 81,206.67 \\ \hline \hline \end{tabular}
\end{table}
Table 19: Equipment and installation cost of air conditioning system.