A fireplace connects with something imbedded within the human spirit. In prehistoric times our ancestors gazed in wonder and contemplation at the crackling flames they relied upon for warmth and cooking. A roaring fire remains fascinating to humans tens of thousands of years later, except for most of us those flames are a luxury rather than a necessity.
Romance aside, it is hard to imagine a more uncomfortable and inefficient form of home heating. A roaring fire can suck as much as 1,500 cubic feet a minute of interior air up the chimney. That is air heated by your furnace, heat pump or boiler. The toasty feeling you get sitting near the flame disguises the fact that if you stand a few feet farther away you will feel colder than you would without a fire going.
As heated air goes up the chimney, colder air from outside is being sucked in to replace it. The colder it is outside, the more pronounced this effect; and the bigger the fire, the greater the energy deficit. Glass fireplace doors can significantly reduce the energy loss. But this involves an aesthetic tradeoff, since flames are less compelling when closed off. When the fire burns out, an open damper continues to draw heated air out of the house. So be sure to close the damper when the fireplaceis not in use.