Drill hole in backside of hearth to vent hot air to other side of wall ??

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New Member
Oct 27, 2023
t7y 1g5
Hi, first post here. I have lurked as a guest reading what I could to setup my insert. After setting up all the pipe and it working well I took the advice of sealing up the hearth right above the insert. That was a lot of custom fun, taking everything out again and laying on my back with sheet metal and rock wool all over again. It definitely increased the efficiency of the whole system though. Now we have some more questions regarding the brick/cinder.

We installed an insert into an existing chimney, it's been working great and pumping out consistent nice heat for about 2 years now. It is located on an interior wall so the side the hearth is open to gets great heat. I just bought a DC ceiling fan that would sit right in front of it to move the air around better. It still takes a while to reach the other side of the wall. The wall has opening on both ends and you can run around the house (kids do) in a circle pattern all day. The fireplace is on the 2nd floor. There is a nice brick hearth around the fireplace with cinder block going to the basement (original fireplace ash cleanout) and all the way up to the roof. The roof has brick above the roofline.
What we have been thinking is making a hole in the masonry right behind the insert and of course below the hearth seal/smoke box I custom installed. We would have a fan connected to the inserts temperature controlled fan, and would blow hot air to the other side of the wall. The wall would be properly setup for the temperatures of course as it is drywalled now and you cant tell there is a chimney from this side. What we are wondering is how the hole would affect the vertical strength of the wall and how much heat would we actually gain from this ? We were thinking a round 4 -6" hole with a fan place inside the hole or inside stovepipe in the hole.
Having seen double sided hearths - that would be great and a dream setup, but an engineer, lots of masonry work and many dollars would need to be brought in to open it up that big !! It just sems a waste to have all that heat so close yet so far to the wall in backs onto.

Any thoughts on this?
Sounds like a code violation to compromise the required 8" of masonry surrounding the insert. It would be simpler to put a table or box fan at one doorway, placed on the floor, pointing toward the stove room. Run it on low speed. It will blow the cooler air down low, toward the fireplace room. The denser cool air will be replaced with lighter warm air from the stove room. Running this way you should notice a faster room temp rise and more even heat distribution.
We did look at some circulation fans yes, I'll look again and see if they come in DC and have super quiet technology.

Considering that the ash door is at the bottom of the chimney in the basement there must be some allowance for (hopefully an overengineered load rating wall) having an opening/hole in the masonry ? The problem before it is all setup and holes are cut, is that the hope of a decent amount more of heat is currently just guesswork to how much would actually come out of the hole and provide for the room . It would need to be noticable change to warrant the all the cutting and patching/wiring. It would be as reversible as a dent in a car, just time and money but always more than your figure.

With fan placement, we have to options at each end of the wall. One end of the wall has open basement stairs coming up. I'm wondering if the fan should come from that side of the wall as to pull cooler air from the basement ?