Originally Posted by tpbrady
Insulation is the answer as the heat loss through the windows is substantial. It also reduces condensation if a desiccant of some kind is placed between the windows.
I put them up before I crossed the Atlantic (1/2" Lexan on the outside) with the intent to take them off upon arrival.
Four years later, they are still on, though I have resealed them a couple of times.
I discovered that being in cool climes like Northern Europe, they totally cut out any condensation.