This research highlights the significance of insulation and glazing area to increase energy effi-ciency in buildings and reduce fuel consumption and environmental pollution. With the prop-er combination of window glass area and insulation in the wall, heating and cooling loads and therefore fuel consumption and emissions can be notably reduced. Therefore, the basic goal of this study is to numerically research the impact of window glass area on insulation thick-ness, fuel consumption and emissions under dynamic thermal conditions for south orienta-tion in the climate of Elazığ, Turkey and to fill knowledge gap in this field. For this goal, the window glass area on the wall which has different insulation thicknesses was enhanced from 0% to 100% with an increase of 10%. The annual heating and cooling loads were computed employing an implicit finite difference procedure taking into consideration that the window is single-glazing and double-glazing. The annual heating loads obtained were used for the optimization of insulation thickness. The results indicate that the heating load in 20 mm insu-lated wall for single glazing is acquired to be 177.57, 236.79, 317.51 and 398.23 MJ/m2 year for values 0%, 20%, 40% and 60% of the glazing area, respectively while it is obtained to be 177.57, 114.24, 88.24 and 76.81 MJ/m2 year for double glass. It is observed that choosing smaller glaz-ing areas in insulated walls containing a single-glazed window results in less heating load. It is also observed that at lower values of insulation thickness, the large double-glazing area on the south facade notably reduces heat loss. It is revealed that the increment in the glazing area for single glass induces an additional heating load, fuel consumption and emissions.