I don't have to worry about it so much here as the temp stays nice enough year round that extra clothing and/or blankets would work for the few months of the year that it gets 'cold' (avg winter high is 69.9, avg winter low is 43.3) with one or two nights a year below 32-34.. but the house I grew up in only had an old natural gas wall heater in the living room for heat in the winter (avg winter high of 65.8, avg winter low 28.6), which was on the far side of the house from my room, and I kept my door closed which further lowered the almost ineffective use of the wall heater that was just about as far away from me as it could be and still be in the same house.

Luckily I had east and south faceing windows so the sun shone in at least one of my windows for most of the day. I found that if I taped flat sheets of clear plastic over my windows that my room would stay much warmer (relatively speaking) day and night. Of corse I still used a wool blanket, light down comforter, and an old square cut synthetic filled 0 degree sleeping bag on my bed at night when it got real cold.

I still keep some of the large drop cloth sheeting on a roll in storage from back then.. if I needed to do it now for an emergency I'd hang several 'walls' of plastic from the roof a foot or so apart and at least one plastic 'roof' in the smallest chamber to reduce the size of the area I had to heat... though pitching the small tent inside would do the same thing and be less work..

PS the avgs are over the last 100 years and seem a bit high to me.