Research on regional residential buildings is an important means of exploring the natural climatic adaptability of buildings and the sustainable development of culture. It is also an important path of sustainable social development. However, current research methods for architectural space find it difficult to clarify the internal and external relations of space, and the function of architectural space to adapt to the regional climate and cultural heritage is difficult to quantitatively analyze and measure. This study constructs a new research method of architectural interiors/exteriors, takes the traditional residential buildings in Wu-style architecture in the Jinhua area as a case study, summarizes the types and characteristics of the interiors/exteriors of Wu-style architecture, and reveals the spatial construction rules of the internal and external types realizing environmental sustainability and traditional residences. The results show that: (1) the architecture of the Wu style has five typical types of interior/exterior, and the regional representation of its interior/exterior is affected by both the human and the natural environment; (2) influenced by traditional Confucian culture, the architecture of the Wu style shows a central axial secondary buckling type and an enclosed type of interior/exterior form, which has the value of the times to coordinate the relationship between people in today’s society; (3) in terms of ventilation, daylighting, and heat dissipation, Wu-style buildings flexibly use the slender gray space form and wide cornice for the internal and external space transition, which effectively improves the ecological efficiency of the buildings’ ventilation, lighting, heat dissipation, etc., and has important reference value for the development and utilization of traditional buildings and the architectural design of new dwellings. At present, this new research method for the internal and external spaces of buildings still has considerable potential and needs to be deepened and improved through further research.