Open fireplaces suck a huge amount of air from the room. It was once explained to me that in one particular case (a specific house) the open fireplace would typically suck 150 cubic meters of air every hour, when that was replaced with a wood stove it went down to 15 cubic meters/hour. So, an order of magnitude of difference. Those numbers shouldn't be taken as accurate of course, but at least that house got much warmer simply because they didn't have all that air sucked in from outside all winter.
reply