The development of global nature reserves is currently in a rapid growth phase. One of the key challenges in establishing nature reserves is balancing environmental protection with rural residential development within these areas, where housing plays a crucial role in the built environment. Successful residential architecture in nature reserves typically meets residents’ diverse needs and environmental protection requirements by considering regional ecology, culture, economic conditions, natural environment, indoor thermal comfort, and energy consumption. This study examines rural residential buildings in the Mengda National Nature Reserve (MNNR) under cold climate conditions in Western China. Through surveys, architectural mapping, and thermal–humidity environment assessment of typical residential buildings across multiple rural communities within the nature reserve, this research explores possibilities for improving indoor thermal comfort in nature reserve residential buildings. Combined with local climate adaptability and architectural design characteristics, this study proposes rational spatial improvement strategies. This study explores climate-adaptive design in the MNNR, integrating passive solar energy and sustainable heating. It proposes spatial strategies to reduce energy use and enhance thermal comfort. The research findings provide a valuable reference for the spatial optimisation of rural residential construction in nature reserves under similar climatic conditions.