I was always under the impression fireplace efficiency was horrible hearing single digits and some claims that you lose more heat than you gain. Friend of mine had his fireplace going yesterday one of those with the steel lined firebox but no double wall or fans or vents,just the lever to close off the chimney when not in use. THis thing was throwing so much heat that he had to open the main entrance door to let some outside. Was about mid 30s outside and the house was 80+ with just a few small logs burning slowly. House is split level about 2000 SF so-so insulation none between the floor and an unheated BSMT. 40 Year old house with heat pump and electric BU.
He claims the trick is to just open the flue just enough so the smoke exits but not too much so all your heat goes with it.
He claims the trick is to just open the flue just enough so the smoke exits but not too much so all your heat goes with it.