Analysis of Energy Saving of Building Envelope in Hot Summer and Cold Winter Region—Take an Office Building as Example

The climatic conditions in hot summer and cold winter region are special, which is the hottest region at the same latitude except for desert areas in summer, and the coldest region at the same latitude in winter. The building envelope in this region is therefore a more complex option than in other regions to achieve the Double-carbon target. This paper simulates and derives the single best retrofit scheme for different envelope structures via a basic model of CAD and Tianzheng energy-saving software, as an example of an office building in Zigong City. The study showed that the energy-saving rate of external walls in the region was 5.74–7.86%, roofs were 5.11–7.39%, external windows were 9.11–11.88% and shading was 3.09–10.95% respectively. Some recommendations are provided for the energy-saving design and retrofit of building envelope structures after comparing the energy-saving rate of different parts of the envelope in hot summer and cold winter regions.