Increasing fireplace efficiency without an insert?


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Old 11-23-20, 12:41 PM
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Increasing fireplace efficiency without an insert?

This is our fireplace:



I'm well aware that open fireplaces pull heat out of a house while operating and the only way to really heat a home with a fireplace is to stick an insert into it. That said, I just can't do it-right now the fireplace opening is about 24" x 40". Going with an insert would shrink the viewing window to not even of a quarter of what it is now. I have a super efficient Buderus wood boiler and I have a small wood stove at the other end of the house on the first floor, so the fireplace is almost purely ornamental/atmosphere, but a little more efficiency and a little less draftiness when not in operation certainly would not hurt. The biggest ticket item on the list would be sealed doors:

https://www.wilkeningfireplace.com/

These guys make a door that is essentially like putting a wood stove door on a regular sized fireplace opening complete with pyro-ceramic glass, cam-locks and a sliding draft control:



They would run about $2,100 for my application. I also found this company which makes what they claim is a more efficient grate along with steel firebacks which I had planned on trying anyway:

https://www.gratewalloffire.com/

My fire box is about 32" wide at the rear so I was going to go with their 31" wide grate and matching 31" wide by 1/2" thick fireback. The final consideration is the chimney. Our fireplace has a massive 13x13 square clay tile liner which is about 20' from the throat of the fireplace (from the smoke shelf to the start of the clay) to the top. I was told that putting a sealed door on the fireplace opening (and thus limiting the intake air) would cause the draft to suffer, and that the gases would lazily make their way up the large flue, cooling as they went, forming creosote. This did make some sense to me, so I did a little research on fireplace flue sizing. Utilizing the 10% rule my flue size should be 11" diameter or about 96 square inches as opposed to 169 square inches now. I would plan on installing a stainless flex liner and then pouring in vermiculite between the stainless liner and the old clay.

Doing all of this work myself would cost just shy of $4,000, which is about the same price as a good insert and liner with me doing all of the work. However, I figure the benefits would be as follows:
  • Sealed doors would mean no more conditioned air escaping (in summer and winter) when the fireplace is not in use.
  • Elimination of the strong BBQ pit smell in the living room on humid days.
  • We would still have the ability to simply open the doors, draw the screen and enjoy an open fireplace.
What I am most curious about is how the fireplace would perform with the doors closed while operating. Again, if we're sitting by it, 90% of the time it will be open, however, usually before going to bed, I'll let the fire die out to the point that it is safe to close the tempered glass doors that we currently have. With the new ceramic glass doors/draft control, liner and efficient grate/fireback I could load the firebox up, close the doors and turn the air down just like with a woodstove and see how much heat is given off. I certainly don't think it will be as much heat as an insert, but I have to believe it will be more efficient than it is now.
 
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Old 11-23-20, 03:15 PM
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I love a wood or peat fire! Experimented in my two previous homes (1969 - 2004) and found closing the glass fireplace doors such as shown in your first image (not a stove) worked nicely: If the room with the thermostat has a fireplace and is above thermostat setpoint, the heater's not running and you're saving energy - despite "cocktail party chatter" logic that says otherwise. AND the aesthetics can't be beat! With peat, there's also the aroma reminiscent of driving down into Irish village valleys.
 
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Old 11-24-20, 08:18 AM
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With the new ceramic glass doors/draft control, liner and efficient grate/fireback I could load the firebox up, close the doors and turn the air down
Creosote build-up would be a concern trying to run a fireplace like a wood stove.
 
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Old 11-24-20, 08:39 AM
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Creosote build-up would be a concern trying to run a fireplace like a wood stove.


Maybe the answer is to make the fireplace more like a woodstove? The more I think about this, the more I am asking myself the following question: If an airtight door with a heavy frame, fiberglass gasketing all around, pyro-ceramic glass and an adjustable air control is fitted to the front of a masonry fireplace, how is that different than installing an insert? Does the firebox with its new airtight door not just become an "insert" albeit with a much larger firebox and a much larger loading door? The only thing I can think of at that point is the chimney. If I were to install an insert in the same fireplace, the first order of business would be a liner because the huge 13x13 clay liner would be much too large to vent the insert through. What if I were to install a 10" (or smaller) liner in an effort to keep the velocity of the flue gases up. With a regulated air supply and a properly sized flue would the whole thing not function identically to a basic, non-EPA wood stove? Obviously the main difference would be that any heat imparted to the room would be radiating from the glass and/or the stonework on the face of the fireplace, and unlike an insert, there would be no blower to carry the heat further into the room. Thoughts?
 
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Old 11-24-20, 11:22 AM
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so considering what your spending why cant you do an insert and liner obviously cost is not the issue seems like an insert is your best option rather than trying to increase the efficiency of an old fireplace and spending the same amount.
 
 

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