<p>Historic buildings reflect the architectural features and construction techniques of the era to which they belong. They provide detailed, concrete information about natural ventilation, lighting, drainage, heating, and cooling, namely, about the functional systems of the region and the era, and thus serve as an important source of inspiration and as a guide and contribution to the sustainable design of buildings in today's fast-growing construction industry, where the protection of the environment and human health has become increasingly important. Therefore, this study aims to develop a score-based comprehensive method to evaluate the unique functional systems of historic buildings in order to investigate and determine their sustainable and energy-efficient characteristics and utilization in detail. In addition to literature and archival research, field research and national and international standards on sustainable design and energy efficiency of historical buildings were used to develop the method, which was tested on buildings of the First National Architectural Period in Konya. The results showed that the design features of the historic buildings such as settlement and orientation, building form, envelope, elements and heating, cooling, ventilation, and lighting systems were passively designed and offered sustainable solutions and opportunities in sustainable design and operation. Overall, it is shown that unique energy-efficient properties of functional system solutions in historic buildings can be revealed through a score-based methodology that can help to make more accurate decisions in the preparation and implementation of conservation and restoration projects, thus contributing to the sustainable preservation of buildings.</p>