## 4 Conclusions  
This research explored the potential of building energy performance simulations as a viable solution for the design of energy-efficient buildings. The research included an operating facility from a small house to a big storage place. Tested buildings included a house, office, and warehouse. Various window, wall, and roof materials were investigated in order to compare their energy efficiencies. Moreover, the orientation of the buildings were also examined for optimum performance. The ASHRAE and US-LEED guidelines were followed and the results generated through Green Building Studio and Insight were evaluated. Initially, ASHRAE 140 was used for the model testing of a small room. The cooling and heating load analysis of the tested small model were within the ASHRAE 140 limitations. It was observed that low e-insulated glass with argon gas was the most energy-efficient window material. Similarly, the three-pane glass window also showed major improvements. It should be noted that the tested wall materials for the house and \begin{table}
\begin{tabular}{c c c} \hline Buildings & **Simple Payback Time (SPBT)** & **Return on Investment (ROI)** \\  & **(Years)** & **(\%)** \\ \hline House & 54 & 1.85 \\ Office & 13 & 7.69 \\ Warehouse & 14 & 7.14 \\ \hline \end{tabular}
\end{table} 
Table 13: Payback time and return on investment results. \begin{table}
\begin{tabular}{c c c c} \hline Buildings & Windows & Walls & Roofs \\ \hline House & WN1 and WN4 & WO1 and WO9 & RO2 \\ Office & WN1 and WN4 & WO1 and WO9 & RO2 \\ Warehouse & n/a & WH1 and WH4 & RW2 \\ \hline \end{tabular}
\end{table} 
Table 12: Combinations used for LCCA. office buildings were the same, but different wall materials were investigated for the tested warehouse building. Walls made with wood exhibited comparable performance with the conventional brick wall for the tested house and office buildings. A wooden roof without insulation showed higher energy consumption for the tested buildings. It was observed that the windows-to-wall ratio (W/W) played a significant role in the consumption of energy for the house building. For instance, an approximately 80% increase in energy was observed for a W/W of 95% for the tested house building. However, for the office building, a relatively lesser effect of the W/W was observed. Moreover, the position of windows showed a lesser effect on the energy performance of the tested buildings. The most optimum position was at the center of the wall in comparison with top and bottom locations. The energy use ranged from 94 to 96 MJ/m\({}^{2}\)/year and from 851 to 875 MJ/m\({}^{2}\)/year for the house and office building, respectively. The orientation of a building depends on the symmetry of the structure. The tested office building was more symmetrical, and therefore less of an energy difference was observed due to the various orientations. A detailed point-based analysis for the US-LEED certification showed that the tested building may achieve Gold certification and Platinum certification for the tested office and warehouse buildings. The life-cycle cost analysis (LCCA) showed that around 54 years was required for the tested house building to recover the initial cost due to its higher energy consumptions during nighttime. On the other hand, the office and warehouse building takes the advantage of a fast cost recovery because the main usage for them is daytime usage, which can be recovered through solar panels. It can be concluded that the simple design implementations can ensure less energy costs and a better living environment. Energy-efficient designs are the viable solution to the energy crisis in developing countries such as Pakistan and should be further encouraged. The Building Energy Performance Simulations (BEPS) make the energy calculations easier. The Green Building Studio is user friendly and provides concise results. The Insight software not only provides results but also suggestions for improvements. The US-LEED certifications is a very good initiative.