The thing to remember is to keep as much heat as is available from getting away. There is residual heat in your home, your body is a natural source of heat, and the sun is a wonderful solar heater. In combination, these can get you through in comparative comfort. Block this room off and put cardboard and blankets over the windows at night to minimize heat loss. Put on several thin layers instead of one or two big bulky garments.
Thermal underwear is good.
The body burns food to produce calories, which keeps you warm. Open those cans of food that need no cooking and make sure that everyone eats something. If frozen food starts to thaw in very cold weather, put it outside in a shaded spot away from animals. Wear plenty of clothes plus a hat. Remember, the human body gives off heat.