Good window size???

Well I am getting ready to order the windows for the doors and wanted to get your opinions. In the pic below I have attached a piece of hardboard to show what the actual window will look like mounted in the door. The dimensions are 12"x18". The windows are only $60 each so very affordable. Let me know if it looks proportional to you and weather or not it will let in addiquate air. There is going to be a fan in the ceiling directly between the windows....... Thanks in advance!!!!
