Ironically, keeping warm in a snowcave may be easier than trying to keep warm at home. You may not really have a small enclosed space at home where a couple candles could stabilize the air temperature. A closet might work, if it wasn't too small to lie down comfortably in with all your blankets and such. Bathrooms are usually the smallest rooms in the house/apartment besides closets, but all that plumbing and tile might just suck all the heat away.