## 4 Conclusions  
Tubular houses, named for their narrow and long forms, are common in southern China. They are a good example of a regional building that is adapted to the local climate. According to the results of field measurements, the thermal environment of traditional tubular houses is not always optimal, whereby both the cooling and heating loads account for approximately 27% of the total energy consumption. Thus, energy-saving renovations of tubular houses should focus on both winter and summer, especially in the months of July, August, January, and February. On the other hand, April and October are the most comfortable seasons, with average outdoor temperatures of 16.2 \({}^{\circ}\)C and 19.2 \({}^{\circ}\)C; as such, the energy consumption during these seasons is almost zero. In the CASE-B to E simulation, different energy efficiency measures were evaluated in terms of their effects on annual energy consumption. The results show that various levels of reduction in energy consumption (varying from 1.6% to 30.5%) were achieved by combining different renovations. Among them, using solar energy with a sunroom was found to be the most effective approach, with an energy-saving rate of 28%, followed by the approach of attaching insulation to the walls and roof, with an energy-saving rate ranging from 13.2% to 30.5%. Furthermore, it was found that the energy-saving rate decreased slowly when the thickness of insulation materials was increased beyond 30 mm, according to the trend of the logarithmic curve. Thus, considering the economic factors, it is recommended to choose 30 mm XPS, which was found to be the most efficient. Additionally, attaching a sloping roof with an air gap to the top of the house was also successful, with an energy-saving rate of 16.3%; however, double single-glazed windows provided little reduction in energy consumption, with an energy-saving rate of only 1.6%, owing to the small external window area of tubular houses. The relationship between energy consumption and XPS material thickness was also established using a highly fitting logarithmic curve. The specific energy consumption (EIR) and thickness of the roof insulation material XPS (N) were fitted to the following logarithmic function: EIR = 177.469 \(-\) 7.317 \(\times\) ln(N), with a fitting index \(R^{2}\) = 0.969 and a Pearson correlation coefficient \(p\) < 0.0001. The specific energy consumption (EIW) and thickness of the wall insulation material XPS (N) were fitted to the following logarithmic function: EIW = 194.114 \(-\) 14.173 \(\times\) ln(N), with a fitting index \(R^{2}\) = 0.986 and a Pearson correlation coefficient \(p\) < 0.0001. This conclusion can effectively guide the choice of insulation material thickness in the energy-saving renovation of tubular houses. The best integrated optimization measures for tubular houses in northern Zhejiang should be conducted as follows: CASE-B + CASE-C (30 mm) + CASE-D = CASE-X, with an energy-saving rate of 47.4% compared with CASE-A. The total renovation cost is CNY 41,143.1, and the payback period of investment is within 5 years (4.75). This study showed that the application of environmental adaptations to tubular houses, along with improved thermal insulation, can drastically reduce energy consumption. If this is inherited as a component in the process of urbanization, it will aid in energy conservation and natural ecosystem protection in southern China. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Component**} & **Energy-Saving Materials** & \multirow{2}{*}{**Price (CNY/m\({}^{2}\))**} & \multirow{2}{*}{**Area (m\({}^{2}\))**} & **Labor Cost (CNY/per)** & \multirow{2}{*}{**Total Cost (CNY)**} \\ \hline Insulation roof & 30-XPS & 80 & 77.04 & 80 & 12,326.4 \\ \hline Insulation wall & 30-XPS & 80 & 30.56 & 80 & 4889.6 \\ \hline Sunroom & Aluminum frame window & 120 & 23.76 & 80 & 4752 \\ \hline Sloping roof & Reinforced concrete & 150 & 83.376 & 80 & 19,175.1 \\ \hline Total cost & & & & & 41,143.1 \\ \hline \hline \end{tabular}
\end{table}