## 3 Experimental Verification
### Actual Vehicle Evaluation  
Next, we evaluated the headliner insulation performance by mounting the headliner onto the actual vehicle. We assumed the following conditions for evaluating the actual vehicle heat load:  
* IR is possible and testing is carried out in a chamber that can enter the vehicle. * The IR irradiation conditions are based on the surface temperature of 100 \({}^{\circ}\)C on the vehicle roof panel. * In summer, indoor temperature rise can occur due to sunlight. * In order to check the indoor temperature increase due to sunlight in the summer, the outdoor temperature is maintained at 35 \({}^{\circ}\)C and the vehicle roof panel temperature is maintained at 100 \({}^{\circ}\)C.
* In summer, cooling starts after checking the room temperature rise due to outside parking. * The winter season outdoor temperature is assumed as 0 \({}^{\circ}\)C in the absence of sunlight. * The indoor air-conditioning is temperature 23 \({}^{\circ}\)C and the blower shift position is set to 5; the same blowing condition is applied for both cooling and heating. Figure 17a shows the actual vehicle test environment, with Figure 17b showing the interior of a vehicle equipped with our thermal load evaluation equipment. The actual thermal load evaluation equipment affords the following features. * Measurement and analysis of real-time indoor temperature. * Remote up/down and left/right movement of the thermal imaging camera. * Insulation cover that can be applied to prevent the thermal damage of the imaging camera. The actual thermal load evaluation results are shown in Figure 18. Figure 18a shows the indoor temperature characteristics in summer, whereas Figure 18b shows the indoor temperature characteristics in winter. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Items** & **Requirements** & **Value** & **Unit** \\ \hline Surface density & Below 840 & 829.5 & g/m\({}^{2}\) \\ Flexural strength & Above 2.40 & 2.46 & kgf/cm \\ Heat-resistant cycle & No deformation & Clear & - \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Headlining insulation performance evaluation result. Figure 17: Actual vehicle evaluation environment: (**a**) Test environment; (**b**) Inside vehicle. The results of the evaluation of actual heat load by season can be summarized as follows:  
* In summer, the elevated indoor temperature is 2.8 \({}^{\circ}\)C lower under outdoor parking conditions. * The indoor temperature is 3.9 \({}^{\circ}\)C lower than the conventional model for cooling outdoor vehicles in summer. * The indoor temperature increases by 7.7 \({}^{\circ}\)C relative to the case of the conventional model when heating the vehicle outdoor in winter. Figure 19 compares the surface temperatures (obtained using a thermal imaging camera) of the headliner between the conventional and improved models when the vehicle is left outdoors in the summer. Here, Sp1 indicates the headliner portion and Sp2 represents the part without the headliner; Table 4 lists the surface temperatures in the two cases. Overall, the improved model affords lower indoor temperatures than the conventional model. In particular, the thermal load characteristics showed an improvement reflected by a reduction of 7.6 \({}^{\circ}\)C in the Sp1 portion including the headliner. Next, we used an actual electric vehicle to confirm the improvement in battery power consumption and mileage resulting from vacuum insulation use. The actual driving evaluation was carried out using \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Items** & **Conventional** & **Improved** & **Unit** & **Remark** \\ \hline Headliner portion (Sp1) & 65.5 & 57.9 & \({}^{\circ}\)C & Reduced by 7.6 \({}^{\circ}\)C \\ Non-headliner portion (Sp2) & 66.7 & 62.6 & \({}^{\circ}\)C & Reduced by 4.1 \({}^{\circ}\)C \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparison of surface temperature. Figure 19: Surface temperature of headliner upon leaving vehicle outdoors in summer (thermal camera measurements): (**a**) Conventional; (**b**) Improved.