In daily life, people spend a lot of time indoors. For this reason, it is important to design closed environments in such a way that they do not adversely affect human health. Especially temperature adjustment is one of these designs. The main goal is to keep indoor environments cool in the summer and warm in the winter. This study investigated window design, which is an important part of the indoor environments. Air, argon and krypton gases used in double glazing applications reduce the window heat transfer coefficient. In the study, a 2D CFD model was created and gas movement was prevented with a transparent barrier placed in a gas environment. In this way, convection effects were reduced and the heat transfer coefficient of the window was interpreted. In the reference state, the window heat transfer coefficient was determined for air, argon and krypton at a gas thickness of 20mm. Then, the gas movement was prevented by the transparent barrier and the new value of the window heat transfer coefficient was compared with the reference situation. It was seen that the window heat transfer coefficient, which was 1.605, 1.122 and 0.875 w/m2K for the 3 gases in the reference case, was 1.398, 0.956 and 0.687 W/m2K with the transparent barrier, respectively. In addition, when the velocities of the gases between the double glazing were considered, it was seen that the fluid velocity was higher for argon and krypton than for air when there was no obstruction. A similar situation was observed when a blocker was placed.