Eeek, I hate to mention plastic again, but here we use 6 mil greenhouse plastic inside and out on the windows and the door we don't use. Not suggested if you have cats as they shred it, but here it works well, we just don't do the inside of the windows in the basement where the cats live
We've put blankets and heavy towels up over the windows when we haven't had thick curtains and I have a feather duvet and a feather comforter, so we manage to keep warm, cooking lots of casseroles does help keep part of the house warmer, but raises the electric bill as I have an electric range.
I wear 2-3 layers of clothes in the house, including a kerchief on my head, they say you lose the most heat through the top of your head and it does help.
We're going to upgrade our insulation next spring and that will be a big help. This house is 40 years old and definitely not insulated well enough.
And I know the ceiling only has that silly styrofoam board in it, the thin stuff at that.
So I've got all the specs from the building inspector and the ok to go ahead with doing it on our own, so next year we will be much warmer.

in the meantime I'm stuffing cracks with old socks or pieces of denim and we still have to put the plastic up.
Take Care All
Lois