Is it more efficient to run 70% fireplace insert or 91% furnace?

• Am no expert. The way I would look at it is to use the fireplace insert for the gas exhaust system is to vent it up the fireplace already in place ( Most likely you are already losing heat up the fireplace). Would not have to punch a hole in either wall or ceiling for fume venting. On the other side , you would have to have copper gas line run to your , most likely , living room /den. That is my thoughts for what it is worth. Good luck ! by fuzzytop

• Furnace. Efficiency ratings are really quite easy. Every time you turn on the furnace, you are loosing 9 cents for every dollar used. In the fireplace efficiency you have listed, you are loosing 30 cents for every dollar used. by BUBBA~THE~POOCH