In order to make the windows be most realistic you must add the proper depth t your windows. An easy way to do this is with the “Solidify Selection” script. Its extremely easy to you use, google for a video tut or intructions.
If you dont want to use that you can select one of the windows by pressing L with your curson over the mesh. Press Shift D. You should automatically be in grab mode. press X to lock the X axis and type in -.02 for starters and see if that looks thick enough or too thin. Once you found a good thickness, SHIFT ALT Right click both edge loops, press F then Skin Faces/Edge Loops and it should build all the necessary faces needed to solidify selections. Press Alt+J to ensure there aren’t any tri’s, however you probably wouldn’t notice anything rendering weird even if there were.
With my experience the IOR in Yafaray changes how reflective the glass is, not how much it distorts what can be seen through it. The distortions are directly relative to the thickness.
However if you still dont want to use the glass material, although I would reccomnd trying it, you can always set the windows to a “shinydiffuse” and play with the transparency tab there. However, it won’t be as realistic. Since your only doing studio renders I’m not sure what the best IOR value would be, depends on your lighting setup since there isn’t much to reflect.
Keep on blending 
