After a few years of planning, materials testing, scavenging, and picking up stuff on sale, design revisions, negotiations, and aesthetic reviews by the better half, I am finally constructing a
RMH in our home. This will be the first full build Iv'e done in a living space so it had to meet a lot of aesthetic criteria. I will post pictures of the build to document the construction and discuss the performance.
Background
The farm was purchased by my grandparents in the late 60's. At the time it had minimal electrical and no running
water. There was, and is, an old
outhouse that was used and the water came from a cistern that the gutters fed into. A hand pump sat in the corner of the kitchen and pumped water into an old trough sink. My grandparents renovated the kitchen and added plumbing, electrical, and an indoor bathroom. The water comes from a spring on the property. There is no insulation in the house. There are two old brick chimneys that are both interior to the house until they go through the roof. A gas furnace was installed sometime in the 70's and vents up the chimney in the center of the house. The southern two thirds of the house has finished second floor rooms. The "attic" over the north end of the house is not insulated, drafty, and is major heat sink to the kitchen and dining room directly below. Winter utilities between gas and electric run average $200 a month the past two winters. Furnace running "winter" weather usually starts sometime in October and tapers off in March/April. Due to some leaks in the roof I have not been able find the source of and seal, I cannot justify insulating the attic floor/kitchen-Dining room ceiling at this point. It may require roof replacement which is not in the budget. The farm has approximately 60 acres of timber that I cut and sold oak
firewood off of in high school and college from the dead
trees that died or blew down. We annually
experience power outages that range from a few hours to a week. An ice storm about 4 years ago took out power for just over a week when my sister was living there. She worked full time and had a small propane catalytic heater to use periodically in the house. I can't expect my wife an two children to do that since they are there all day.
Goals and Requirements
Big picture is to build something that burns
wood (no direct $ cost to me) and will offset the utility bill
enough to justify the construction cost this year. It also needs to be safe to operate and be around as I have young children. Breaking that down a little more;
-
Wood Heat that burns in a safe and efficient manner. I don't feel that traditional wood stoves meet this.
- No utilities required to operate. This knocks out pellet stoves in general although I know there are passive versions.
- Relatively low cost. Buying a traditional
wood stove is not really an option. Building one isn't either although I did it in high school for a welding competition. (I won 1st and the Regional level with that stove)
- Passes my wife's aesthetic check. This knocks out the remaining passive pellet
heaters. It also means no typical cob/plaster surface finish.
- Can be cleanly removed if we decide it just didn't work come next spring. This means direct $$ needs to be low and/or materials that can be recycled elsewhere.
- Needs to increase the comfort level in the Kitchen/Dining room area. Hopefully the whole house.
- Utilizes the existing chimney that sits on the north wall between the kitchen and dining room.
- Small enough to not "take over" the dining room. This also ties into the aesthetic requirement.
- Does not make any more holes in the original wood floor. This ties in with the "clean removal" requirement.
Design
After reading Ernie and Erica's Builders Guide I settled on some form of Pebble Style bench and a 5" system. I acquired several grease drums some years ago and I want to use those for my bell. They are roughly 14" in diameter and 28" tall. Using the 5 Minute Riser design (7" pipe with 1" ceramic fiber blanket liner = 5" ID) I
should have plenty of clearance around the sides of the heat riser for good flow.
The bench will be 22" wide and a maximum of 20" from the floor. My wife requires it to be a comfortable table seating height with a cushion on it so we agreed on 18" from the floor to the top of the bench. This will allow us to use the bench as table seating for the large table I promised to build next year.
With the bench being 22" wide I can get a full 4" of clearance from the wall and not stick out into the room obtrusively. You will be able to see this better in the future photos.
To tie the aesthetics of the RMH into the decor of the rooms the visible face of the bench will be clad in reclaimed corrugated metal roofing from a barn on my in-laws farm. It happens to be left overs from our corrugated metal kitchen ceiling
project. The mass will be high clay content earth from the farm and stones from the creek.
To ensure a clean removal should we decide to remove it someday, I decided to invest in a roll of 24" wide aluminium flashing to lay on floor before mortar leveling the bricks to build the bench on. I realize foil might work, but I know with my two children something would have gone under the bench and the foil torn in the first hour had I used it. Flashing it is.
On top of the flashing will be grey pavers my wife selected. DuRock cement board went down on top of the pavers. The pavers are no more than 6" apart.
2" drip edge will be glued to the cement board with a high temperature rated adhesive to capture the box walls. The sides and back of the box will be cement board and the face will be the reclaimed corrugated metal. J-Bead makes the upper framing to hold it all in place. As fill goes in I plan to add "deadmen" to help keep the walls where I want them.
The surface is undecided at this point, but will be either a smooth plaster or tile of my wife's choosing.
Under the combustion unit I am putting a total of 2.5" of Perlite before the clay fire brick of the
feed tube, burn tunnel and heat riser base. Although the system is going to be a 5" system (19.7 to 20.25 CSA) from feed tube to the top of the heat riser, the bench ducting is going to be 6". I'm hoping for a bit of stratification chamber effect. Total bench pipe run is only 7 feet to a 90 up, up 5 feet to another 90, then into the brick chimney. I'm optimistically hopeful that since the chimney is internal to the house and warm relative to the outside air, and since it's a short run in the bench, my exhaust should have enough heat left to both draft well and continue heating the big heat sink of a chimney. Worst case, I pickup some pipe and line the chimney. I have already checked the internal dimensions of the chimney for pipe clearance and I'm prepared for that possibility.
UPDATE(s):
Cost Evaluation
As one of the major goals of this is to offset the utility costs for the winter I will post some updates in this main post to keep it easy to find.
I already had/keep on hand things like RapidSet Mortar, perlite, ducting, etc. as we are renovating the farm house and I did not have to go out and purchase them.
Items I did have to purchase specifically for the RMH that I otherwise wouldn't have on hand:
Fire brick, I bought 25 whole and 12 splits, but didn't use all of them - $80
Pavers, 42 new pavers - $18
DuRock Cement Board - $30
Ceramic Insulating Blanket - $45
7" Ducting for Riser - $10
Specialty caulking adhesives - $20
Narrow Ridge Corrugated metal sheets - $45
Total direct costs(things bought for specifically this build)
$248
I also tallied up everything if I had to go out and buy all new right now to build it and that total comes out to about $450 not counting any clay or sand for the mass. I won't need to buy any of that for my build, it's all available on site as is all the firewood I will need.