Masonry Heater.....an observation and suggestion

Over Thanksgiving, made trek to north to spend holiday with spousal unit's family. A major feature of the home where we stay is a large fireplace (wish I had taken a picture). Fireplace measures about 8 feet wide x 8 feet tall (floor to ceiling brick face) with raised hearth and large wood plank mantel. By all accounts, it is a conventional fireplace. One unique twist........on both sides of fire box are hidden air channels. Inconspicuous intake at floor level, exit from holes above the mantel. Once the fireplace gets going, and the mass of it heats up.......warm air starts to rise thru the channel and disperses into the room via convection. Then further dispersed by ceiling fan into the combined living room / dining room (a smallish great room).

As near as I can tell, fireplace does not have serpentine channels or bells in back of the face........I asked and nobody knows. (Keep forgetting to go outside when operating to check chimney for smoke). Guy that built it long since passed so can't ask him either.  They only know if you keep putting wood in it, thanks to the radiant heat off the face and convection heat from the ducts, the room gets toasty warm. And since thermostat for rest of the house is in the same room, the central heat furnace never kicks on, so rest of house goes cold.

One major flaw in the design is the fireplace face is flush with the exterior wall, meaning the fireplace does not jut out into the room, rather it juts out into the lawn area beside the home. Three sides are potentially losing heat to the great outdoors. But aside from that, this design has great potential.

First, would include a vertical combustion port along the lines of what Fox Fish does in his videos.....to get a big boost in burn efficiency, then port that hot gas thru bells and/or channels on either side the combustion chamber, and place the build in an interior location away from exterior walls. Have seen these used as wall partitions between rooms (think circular foot traffic around an interior wall). Interior location retains all heat inside building envelope. Depending on the amount of heat needed, one could include the heat ducts or if not needed, just harvest the radiant heat.

The big improvement is the combustion port to increase  burn efficiency. Something convectional fireplaces.......and maybe most masonry heaters......do not have.

Long ago when I lived in New England, it was a common feature for fireplaces (most on an outside wall) to have what I think was called a heatilater.
A steel insert with air chambers (baby bells) and an electric fan to move extra heat into the room, and they did a good job.
Your inlaws fireplace sounds like a handmade version that does not require electricity.
It sounds very cool, a picture would have been nice.

Almost all those old farmhouses eventually ended up with a steel chimney insert and a large cast iron box stove replacing the fireplace.

My parents built heatilator fireplaces into our house in the late 50s/early 60s. Metal firebox, with a metal shell around it, and ducting to low inlet and high outlet grilles. No electricity. As we didn't have ceiling fans, I don't know how much they actually added to the comfort in the rooms. At least the fireplaces (and furnace and basement potbelly stove flues) were in a central masonry mass.

Is this similar to what you all remember?


(source)

A blurb from the Northline Express article:

Heatilator fireplaces, also known as "old-style zero clearance fireplaces", are a combination of heater and ventilator and are by their nature, fireplaces that circulate air. Old-Style Heatilator Fireplaces use a special venting system that draws in cool room air and releases it as warmer air. The air that is in the venting system never goes through the firebox so it doesn't get fouled with ash, smoke, or other unpleasant odors. Instead of pushing air through the firebox, Old-Style Heatilator Fireplaces route air around the firebox and allow it to heat, without any of the drawbacks associated with traditional fireplaces.

Yes, that is what I remember.
I also remember that replacing the fan must have been a big deal, as on quite a few the fan no longer worked.

The heatilator is what ours is/was. If that was more efficient than a simple fireplace, then, the actual fireplace would have been a negative efficiency, even with the whole thing inside the house.  We now have a woodstove. This one actually keeps the house warm, but we're blowing through firewood like lightening - and it's killing my back. Oh, how I'd have preferred a good masonry heater, instead!

The fireplace Carla has is about 90% same as the one they have up north. That one is a bit wider, but the heat ducts are to the right and left of the firebox.....inlet at floor level below hearth, outlet above the mantel, about halfway to the ceiling. That one is all masonry.....no metal firebox and no fan. Air ducts on convection......warm air rising. After an hour or two, face of fireplace is hot to the touch, so is radiating. But still consumes a lot of firewood and harvest very little of the available heat.

Not sure of the design of that firebox, but most have a metal damper to close them off to outside air, but other wise are a straight masonry chimney. Hopefully lined with firebrick for at least part of the way up.

This is a link to a masonry heater design. As youtube videos go, major advantage of this one is it shows the flow of flue gases to show how it works. In all these, it seems to me the "oven" is an unnecessary complication, but if it functions as a secondary burn chamber, perhaps it does serve a purpose.



If Carla were to replace her old fireplace with one of those, would be all grins and giggles.

There are hundreds of interesting builds of masonry heaters posted by the euro and russian builders. Unfortunately, I don't speak or understand those languages. Would be nice if they would also include the animations to show flows........which explain the internal porting.

Great opportunity for aspiring young brick layers. There are literally millions of homes with worthless and therefore unused fireplaces that can be replaced with fully functional masonry heaters.

Failed to mention......the variation on this heater would be to include the air ducts. On the video, in place of the vertical divider (between the orange flows) would be two walls, with air space between them. Inlet below, outlet above. That allows you to fast pump hot air into the room. Then, if you include a damper in the design, you can shut that off and rely strictly on radiant heat.

Also ........batch box with port above the fire, as demonstrated by Fox Fish. If you want dramatic, put a glass door in the oven portion to watch the ram's horn vortexes flow.

For those not familiar with Fox Fish and his experiments..........