Energy retrofitting of existing buildings can be achieved by replacement of existing windows with energy efficient window types as well as improving the insulation of the building outer shell. In Turkey, there is considerable need to classify and determine the feasibility of windows in retrofitting projects. This paper presents research on glass types in the Turkish market that can be used in such projects and reviews the recent technology for energy-efficient glass material. First, the thermal performance criteria of energy-efficient glass types are analyzed. Second, energy-efficient glass types produced in Turkey are evaluated according to thermal performance criteria such as U-value (U), solar heat gain coefficient (SHGC), and daylight index (Dx). As a result, the study presents a brief evaluation of current energy-efficient glass types, which are feasible and optimal for retrofitting the existing Turkish building stock.