I live in an old farmhouse built around 1910. It has always had wood heat only. 3 chimneys. We want to change the heating source....an 84 year-old Mom who doesn't need to lug wood! Would a ventless gas (propane) fireplace....or a direct vent gas fireplace be efficient in an old house? Are they appropriate as a main source of heat? Can you leave them on overnight, sleep in same room with them? What heating source would you recommend? The house is the basic "T" shape and we generally only heat the older, kitchen part (with transom to upper floor.) Bedrooms are unheated....and COLD! Any suggestions? My thought is that the gas fireplace would be quick and simple and fit the period of the house well, IF they are safe as a the main heat source. And econimical.