about 300 pounds of masonry moderates a small space
This time of year I don’t usually get too muddy, but I brought some mud into my office last month so I could have a better and more efficient source of heat — finally! This little “heater hat” effectively turned my little iron box stove into a mini-masonry heater — with an oven! (note the wooden door on the right, just above the iron stove door). The wood that used to over-heat me, briefly, in the morning, now keeps me comfortably warm all day, and into the next morning (depending on how long I fire it and how cold it is). And, unlike most iron stoves, it doesn’t generate that fierce, drying attack-heat that people try to moderate, either by burning wet wood, or by damping down their fire so it heats minimally and smokes prodigiously.
The stove was an old cast-off that now provides clean heat from a clean fire. The surface temperatures of the heater portion are much lower than hot iron and (except for the tile, which gets hotter), very huggable. In addition, I lined the firebox with brick, which keeps the metal surfaces cooler and safer, but increases internal combustion temperatures for a cleaner burn. Once hot (which takes up to about 10 minutes), no visible smoke comes out of the chimney. I typically burn it for less than an hour and have heat all day (I live in western Oregon, so it’s not that cold). In my under-insulated cabin, the “hat” usually holds heat until the next morning. Oven temps vary depending on what and how I’m burning, but we’ve had several breakfasts out of it…).
The ornamental work illustrates the flame path: exhaust gases vent out the back of the stove (to the L. in the photo), then go up and around the oven (to the R.), then back up (on the L.), then in a zig-zag pattern through the narrower section on top, from L to R, then back again, and up. The core is built from a couple dozen or so firebrick — mostly splits — and some old bits and pieces of ceramic flue tile, all covered in mud.
Hi Kiko,
Thanks for sharing this information…..this is really huge for someone like me that lives in Maine and is searching for cost effective ways to heat more efficiently….this comes the closest I have seen to the “common man” masonry heater. I have a Jotul wood stove and would like to duplicate what you have done…I understand at a basic level your description of how the hot gasses move but it would help me allot to see exactly how you achieved the path you describe in pictures. Do you have pictures of the build or maybe a drawing you could email or point me to? If not could I compensate you somehow to produce some thing like that for all of us?
Best,
Dave
After doing a masonry heater workshop with Albie Barden last year, I started dreaming up a similar, but modular add-0n system for iron stoves, looking for lightweight materials with good thermal properties. I didn’t get very far, but this beautiful example gives me new inspiration to keep working on it! I’m curious how you configured the flue – straight into the chamber of the add-on, or through a longer path that maximizes thermal transfer (similar to masonry heaters?) Thanks.
The path is maximized as follows: flue enters the masonry unit on the left; the bottom, wider section is designed somewhat along the lines of a bell stove, and includes the (small) white oven; then flue gasses go back up at the rear left (out of sight); then they travel from left to right, then up, then right to left, then into the metal pipe.
“Lightweight materials w/good themal properties”? Isn’t that a contradiction in terms?
Kiko… A brilliant idea. Maybe I live under a rock but this is the first I’ve seen of this. We have a well made, efficient stove, but still experience the swings in room temp and I am not satisfied with the amount of smoke that comes from our unit when it is not running hot. This just might solve two problems in one. A great permaculture idea.
Many thanks for sharing… Bill
Hey, Bill, thanks for writing. I’m excited about this idea too; let me know if you try it! I want to do a few more of them myself. Seems like a worthwhile place to experiment. — Kiko
Hi Kiko,
I’m sure this set-up will generate lots of interest for people with these great old Jotuls and Morso’s. It looks, however, top-heavy and dangerous to me. How about some supplementary support for the upper portion?
Best wishes,
Steve Bushway
Yes, it does look top heavy. Initial design plans did include supplementary support, but I abandoned them after it got built because it was so stable (the chimney connection helps). Shock absorbent pads under the feet of the stove — to dampen vibration in a wooden structure — also made supplementary support more complicated — all extraneous to the basic design, which works! Every job is different! — K.