I've got insulating curtains in front of the sliding doors in my apartment; one problem I have is ice buildup locking the doors closed when it gets cold. (<-20C) When warmer than that, it's even worse: the cold glass builds up a tonne of condensation, which can lead to mold buildup. Not sure what do do about that, other than make sure the curtains come open and air the space out fairly often, and wipe down the windows every so often. (Have a dryer apt, I guess-- but then I couldn't dry all my clothes on racks)