This entire thread reminds me of my college experience in the snow belt of upstate New York, living in rented rooms in decrepit wooden buildings that had more drafts than a screen door.
Like M Pearson says above, the whole thing was a hot mess!! (and today most have been demolished, for good reason)
$100 was big money back then (cue that old timey music), and for two years I saved even more money by living in attic rooms that weren't connected to the heating system.
The first thing I did was always seal the windows with that plastic film business. Then put up something to cover them- curtains, blankets. Next, cover the walls- hippie tapestries were the in thing back then, but literally anything would work.
Next, appropriate clothing- a pair of long johns or even stockings, double socks, gloves, hat, scarf. Use all the time. Sleep in a hooded sweatshirt.
Last, pile on those blankets and/or whatever else you have. I had friends who lived in the [also unheated] basement of one of the rooming houses I was in, and during a blizzard one year I went to visit and they had all their coats and sweaters on their beds because it was that bad.
All of these things were great prep for living in other places with serious cold and big snow-- I remembered my friends in the basement one year as I was laying under about 25kg of heavy weighted blankets in an unheated, drafty straw-roof house in Northern Japan during an early blizzard!!
If you can, isolate a smaller space that you can heat up more easily. In my current house, that means closing all the doors and focusing on just one room, whether that is the living room, my office, the bedroom, etc.
