As China's construction sector accounts for 50.9% of national carbon emissions, historic buildings in North China emerge as critical targets due to their low energy efficiency and substantial carbon footprint. This study explores the potential impact of energy retrofittings on the hygrothermal environment and material deterioration of brick walls. First, the Köppen climate classification method was used to divide North China into five distinct climate zones. A representative one-dimensional wall model was established through field investigation, and hygrothermal coupling analysis was conducted across different climate zones. This analysis examined the dynamic behavior of the wall’s hygrothermal environment under complex boundary conditions and assessed the risks of mold proliferation and condensation before and after renovation. Correlation analysis was subsequently performed to identify the key factors influencing the wall’s hygrothermal performance. The findings indicate that, among the common internal insulation systems in North China, those utilizing mineral wool and wood fiber boards may increase the risks of brick wall degradation, with the insulation thickness and vapor permeability resistance coefficient being significant predictors of wall moisture content. The research provides valuable insights for improving the hygrothermal environment of North China’s historic structures following energy-saving interventions.