## 3 Results and Discussion
### Comparison of the Air Insulation Wall and the Basic Case  
During the temperature test of the case study, it was found that the external surface of the building receives long-term direct solar radiation in summer, which causes the external surface temperature to be much higher than the normal outdoor temperature. After measuring the indoor wall temperature and indoor room temperature, the wall temperature was found to be positively correlated with the indoor temperature and indoor wall temperature. As shown in Figure 10, the three temperatures of the building have a parabolic distribution. During the day, between 0:00 and 8:00, the temperature of the outer surface of the building was lower than the indoor temperature, but with the increase in solar radiation, the temperature of the outer surface rose rapidly, exceeding the two indoor temperatures at 8:00. At 15:00, the external surface temperature of the building reached a parabolic peak at a temperature of 67.1 \({}^{\circ}\)C. It took a certain amount of time for heat to transfer from the outer surface to the room, so the temperature of the indoor wall reached its peak at 16:00, at 37.8 \({}^{\circ}\)C. In the same way, the heat transfer between the indoor wall and indoor air also took time. The indoor temperature was not only affected by the wall temperature; the air in the courtyard also transferred heat to the room through the doors and windows. Therefore, under the common influence of the various temperatures, the indoor temperature reached its peak at 18:00, and was 38.63 \({}^{\circ}\)C. Therefore, it can be concluded that the indoor wall surface temperature and indoor air temperature change with the outer surface temperature of the building, and the delay time between them was approximately 1 h.  
After the new system was installed in the building, the heat transfer of the wall was simulated and analyzed. Figure 11a shows the original wall heat transfer process for the case study. The outer surface temperature was 67 \({}^{\circ}\)C, and the heat reached the room after being transmitted through the wall material. The temperature of the inner wall of the room was 49 \({}^{\circ}\)C. This heat continued to exchange heat with the air in the room, causing the indoor temperature to continue to rise. However, as shown in Figure 11b, before the heat from the outer surface entered the room, it was first cooled by the cold air from the cold alley; then, it reached the original wall of the building and finally entered the room. Under the combined influence of the reduced heat consumption through the air wall and passive cooling effect of the new system, the temperature of the inner wall of the room was 37.74 \({}^{\circ}\)C. Thus, the temperature dropped by 11.26 \({}^{\circ}\)C. Figure 11c,d show the heat transfer on the walls and ground of the case study and that of the new system. The building not only transferred heat to the outer surface, the wall near the courtyard was also affected by solar radiation and transferred heat indoors. Between the first and second floors, a heat exchange occurred through the floor.  
Figure 10: Comparison of the building exterior surface temperature, indoor temperature, and indoor wall temperature.