Buy polystyrene foam panels and just simply trim them to fit the size of your basement window. The reason why you would want to do it is that basement windows are sometimes thinner and less insulated than others.
As soon as the broad disk of our lovely sun comes up you better open the curtains and turn off your lights. Believe it or not, they can help more by shining through your glasses than artificial lights on your ceiling.
You Are Paying Double For Your Heating Unless You Know These Tricks