## 3 Results and Discussion
### Optimal Design Solutions and Comparative Analysis of Different Regions
It is worth noting that the LCCO\({}_{2}\) in Yulin has reached zero carbon. Corresponding to the values of the design variables, the building orientation in the two regions is different. According to the analysis in Section 3.2,  
Figure 20: Optimization objectives and variables clustered in a parallel coordinate graph (1, 2, and 3 correspond to window types A, B, and C, respectively). (**a**) Xi’an and (**b**) Yulin. both are in the optimal range conducive to reducing energy consumption. The south and north window-wall ratios, south external window type, and sunvisor overhang length are consistent. The thermal performance of the north exterior window and the insulation layer thickness of the exterior wall and roof in Yulin are greater than those in Xi'an, because of lower temperatures. For the Xi'an region, case-2 has the lowest EC and case-5 has the lowest LCCO2, both of which are the same scheme. This is mainly because carbon emissions are comprise material carbon emissions and operating carbon emissions, of which the latter occupy a large proportion, so they are greatly affected by buildings' energy consumption. This can also be reflected by the scatter relationship between EC and LCCO2 in Figure 5. Compared with case-1, the energy-saving rate increased by 2.8%, LCCO2 decreased by 5.5 kgCO2/m2, TDHP decreased by 0.6%, and LCC increased by 59.6 CNY/m2. For case-3, TDHP has the lowest value, and compared with case-1, the TDHP is reduced by 0.7%, the energy-saving rate is increased by 2.1%, LCCO2 is reduced by 2.9 kgCO2/m2, and LCC is increased by 51 CNY/m2. The LCC of case-4 has the lowest value, which is 55.5 CNY/m2 lower than that of case-1, while its energy-saving rate is reduced by 5.7%, its TDHP is increased by 1.3%, and its LCCO2 is increased by 48.5 kgCO2/m2. For the Yulin region, case-2 and case-5 are also the same scheme. Compared with case-1, the energy-saving rate is increased by 1.8%, LCCO2 is reduced by 7.0 kgCO2/m2, TDHP is reduced by 0.4%, and LCC is increased by 42.5 CNY/m2. For case-3, TDHP is decreased by 0.9%, the energy-saving rate is decreased by 1.5%, LCCO2 is increased by 45.2 kgCO2/m2, and LCC is increased by 61.6 CNY/m2. In case-4, LCC is reduced by 65 CNY/m2, the energy-saving rate is reduced by 8.7%, TDHP is increased by 1.9%, and LCCO2 is increased by 44.5 kgCO2/m2. Comparing the two regions, cases-2, -4, and -5 have a consistent change trend for each objective compared with case-1, while in case-3, the change trend of LCC is consistent but that of EC and LCCO2 is the opposite, which is mainly related to the solar radiation. Because of the cold climate and abundant solar energy resources in Yulin, in order to improve indoor thermal comfort, it can be seen from the value of the design variable in case-3 that the south window-wall ratio is increased to 0.4, which is not conducive to reducing buildings' energy consumption. Moreover, the available area of photovoltaic panels is reduced, which is not conducive to the power generation and carbon sink of renewable energy. Therefore, in terms of optimal indoor thermal comfort, EC and LCCO2 are higher than in case-1. From the values of the design variables, there are also differences in the value characteristics formed under