A wide, open hearth offers plenty of comfort and ambience, especially on a chilly winter night. As for heat - it probably offers less than you think. Indeed, old open-hearth wood-burning fireplaces range from 15 percent efficient to minus 15 percent. Yes, that means your old fireplace could actually be making your house colder, even when it's burning.

Read more about it here.

Source : San Luis Obispo Tribune