What is better, heating a room or heating yourself? When you are thinking on the last option, I have a very simple method. You can use a 12 Volt electric blanket. The only thing you need to do is to make a slit in the center of the blanket, to put your head through. And sewing a collar around the hole with a strip contrasting cloth. To close both sides, use Velcro. With a 12 Volt lead(gel) battery of 12AH you can be warm for some time.