Condensation on Windows - what do you do

Hi fellow campers, been awhile since I posted so thanks for taking time to read my post Just curious what you do to help or possibly stop condensation from forming on the inside of your windows while winter camping. Granted I don't have double pane Windows ( which would be nice ) just standard Windows. We camped this weekend and lows were around 30 and highs were only 45 so I typically run a ceramic heater as much as I can to save on propane but the furnace would occasionally kick on to keep it toasty inside - about 70 degrees. Ever so often I would take a bath towel and wipe the windows down because of all the condensation. Water would actually be standing in the bottom metal frame of the window. I've tried opening a window on each side of the camper just a little but that didn't seem to help either. I've read somewhere that you could put saran wrap on the Windows - didn't know if that would work or not - seems like that would be a lot of work considering the blinds and all you would have to contend with. Just looking for advise from the pros. Thanks again and happy camping.