Energy conservation and carbon reduction in buildings have become important concerns and, at the same time, the value of low-tech approaches employed in indigenous architecture is increasingly acknowledged as a pertinent reference for contemporary design practices. The research on vernacular dwellings in Jiangxi has many perspectives and fruitful results, but not enough attention has been paid to the research on climate adaptation. This article verifies the vernacular dwellings’ climate adaptation and summarizes the low-tech methods embedded in vernacular dwellings, aiming to provide guidelines for future exploration of energy-saving and carbon-reducing practices in architecture. By selecting different types of vernacular dwellings in Nanfeng County, this article verifies three aspects of the ecological characteristics of vernacular dwellings: the light environment, wind environment, and energy consumption, by comparing them with those of local modern residential buildings. It is concluded that the average daylight factor of the hall area of vernacular dwellings is better than that of the modern residential buildings in rural areas, and the vernacular dwellings regulate the indoor wind environment and maintain indoor comfort through natural ventilation in winter and summer seasons. Also, the annual energy consumption of the vernacular dwellings per unit area per year can be reduced by up to about 32% in comparison with modern residential buildings. Subsequently, the article concludes that patio space has a positive impact on the indoor physical environment through comparative experiments. Vernacular dwellings are well adapted to the local climate in terms of form, structure, and materials, and these low-tech methods should be applied to the design of rural dwellings in the future.