Can you increase the efficiency of a gas fireplace with a long exposed flue pipe?
With the death of the Mantis by Empire, and with Nu-Air IFP-45 not yet certified, high efficiency direct vent gas fireplaces seem hard to find.
Add in specifics for you design (linear, 40″+), and it’s basically a lost cause. You are stuck with 65-70% efficiency. Which is a significant penalty for the “ambiance”, when you can’t get a gas furnace that is less than 90% efficient.
My question is, since 30-35% of the heat seems to be going out the flue pipe, could you artificially increase the efficiency by using a long flue pipe and boxing it in with air intake and exhaust vents, to recuperate most of the heat that was going to get lost? I was thinking of having the fireplace on the first floor, and the exhaust on the second floor so to speak. Forced ventilation in the chase would be the last step, but I realize you could go too far and create a “condensing” fireplace with no provisions to deal with the acidic condensate.
Has anyone done this type of install before?
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