In this study, a thermoeconomical optimization of multiple pane window for Iskenderun, Izniir, Kocaeli, Sinop, Malatya, Ankara, Van and Ardahan cities which are located in different climatic regions of Turkey is carried out using the degree-day method. Operation cost in the objective function is obtained for five different fuel sources. The results show that the optimum number of panes in Turkey varies between 2 and 4 depending on the climate zone and fuel type. Multiple pane windows should be seriously considered, particularly in the cold climate zones of Turkey where the amount of lifetime heating energy saving can reach up to 1200$ m(-2). (C) 2011 Elsevier B.V. All rights reserved.