© 2021 University of Split, FESB.Sunspace integration is a simple and effective passive solar technique to improve the energy efficiency of buildings. However, their effectiveness should be evaluated regarding different design parameters and climatic conditions to achieve the most appropriate implementation. In this regard, the impacts of sunspace integration to a detached house in Istanbul on heating and cooling loads are numerically investigated. Various sunspace configurations considering three different sunspace depths, six different glazing unit structures, and the inclusion of active shading devices are examined to reveal the most effective designs, compared to the reference house, which has no sunspace. Both steady-state and transient (annual) analyses were conducted. It is found that the maximum cooling load (16.91 kW) is significantly higher than the maximum heating load (6.17 kW) regarding steady-state analysis for representative days, hence, it is concluded that the equipment selection should be carried out with respect to cooling load values. By the annual analysis, it is revealed that sunspace attachment is significantly beneficial for the reduction of heating load for all considered sunspace configurations. The annual saving of heating energy can reache up to 6.6 kWh/m2 (23.5%). However, attachment of sunspace for the cooling period can cause an adverse effect in some cases and increase the cooling load. Depending on the configuration, a sunspace can attain a yearly cooling energy saving of up to 9.6 kWh/m2 (19.5%), or it may cause an increment up to 17 kWh/m2 (34.5%) with an improper selection of sunspace design configuration. Obviously, this adverse effect is due to the lack of shading device in the sunspace. Besides, the configurations yielding the highest energy saving in heating and cooling periods are different from each other, hence, it is suggested that an optimization study is required before the implementation of sunspace.