## 2 Materials and Methods
### Field Measurements  
It is important to note that the thermal environment of a traditional tubular house is not always optimal. There is much room for improvement in terms of the thermal conditions in such dwellings, with both winter and summer cases requiring particular attention. The thermal properties of the building envelopes are the main reason for the poor thermal environment. A traditional tubular house is always covered by poor envelopes such as a 120 mm reinforced concrete roof, a 240 mm clay brick external wall, and single clear 6 mm windows, according to the field survey.  
A series of experimental measurements were carried out, focusing on the characteristics of the tubular house and local climate in 2019 during winter and summer. Auto-loggers were used to simultaneously monitor the indoor and outdoor air temperatures and relative humidity. These instruments were placed at a height of 1.5 m in the middle of eight zones. There were no active systems in operation when the measurement was conducted. All the field measurements were carried out without active system used, focusing on the characteristics of the tubular house and the current situation of the thermal comfort to provide the basis for the study.  
A general summary of the measurements revealed that traditional tubular houses have particular structural and thermal characteristics.  
The results in Figure 5 show that the arrangement and spatial structure played important roles in making the indoor temperature lower than the outdoor temperature in summer; however, the temperature in some zones was still too high. In winter, the indoor temperature was higher than the outdoor temperature, reflecting the advantages of a tubular house. However, the average indoor temperature was approximately 4-7 \({}^{\circ}\)C; thus, inhabitants would feel cold without a heating method.  
In summer, the indoor and courtyard temperatures of the tubular house increased with height. The temperature difference between indoors and outdoors on the second floor was 1.9 \({}^{\circ}\)C, while that on the first floor was 5-5.8 \({}^{\circ}\)C. In winter, the situation was the opposite. The analysis suggested that in summer, the higher indoor temperature of the second floor was due to insufficient heat insulation by the roof material. In winter, for the zones of the first floor, the heat loss was low because there was no direct heat transfer in the outdoor environment. The temperature of the front yard was slightly lower than that of the back yard because of the higher ratio of width to height of the yard and more sunlight in the former (the width of the front yard is 3600 mm and the back yard is 3000 mm, while they share the same height of 6000 mm). Furthermore, the indoor relative humidity in summer reached 70%. It can be clearly seen that there is much room for improvement in terms of the thermal conditions in such dwellings, with both winter and summer cases requiring particular attention. Thus, a search for feasible improvements is required.  
Figure 4: (**a**) The Image of CASE-A, (**b**) image of new tubular houses with different energy efficiency measures in Sketchup 2019, (**c**) image of new tubular houses with different energy efficiency measures in Cad2021, and (**d**) image of the sum-space windows.