I needed a change and wanted insulated curtains but they are pricey. So I am putting the new ones up (they are on a wooden 1 inch rod, and behind them(since they go with the new ones) I am going to put the old ones up. Like you would a sheer. Then I should have not only block out but insulated. The eastern exposure is pretty fierce and it is a french door. We don't use it much so it doesn't matter if it is all covered.
Now I have new clean curtains all around.