Windows are one of the most important components of the building envelope from which several high level performance requirements are expected. Some of these performances are contradictory with each other which increase the importance of the design and material selection of windows. Natural lighting and thermal performance are examples for the contradictions in window design. Usually when transparency is increased in windows the thermal conductivity of the system is also increasing which decrease the overall thermal performance of the window. Shutters are the components of a window which is mainly used to control the natural lighting through a window system. Another important benefit from the shutters may be its contribution to overall thermal performance of the window systems. As a Mediterranean country several types of traditional window shutters have evolved in Turkey. Istanbul is the historical and economical capital city of Turkey and wooden vertical pivoted shutters are the most common type of shutters in the traditional wooden Istanbul houses. There is also a growing trend in the usage of vertical PU filled aluminium roller shutters in these kinds of houses. Two houses using each other type of shutters are examined in 2012 for determining the most efficient type of shutters in terms of energy usage. An inventory analysis is introduced, a comparative assessment of embodied and operational CO2 emissions on the two case houses' windows is realized and the results are presented in this paper. (C) 2013 The Authors. Published by Elsevier Ltd.