The little red cabin got about seven upgrades so that it is more habitable. Then it was reserved during the workshops. And then for the period up to the workshop a family moved in. And then the family wanted to stay through the workshops.
So one morning there was a log on the ground in front of the shop. By 7pm we had a "porta cabin": a little cabin on skids that we can drag around to wherever we want. Complete with a pocket rocket.
And yesterday I noticed somebody had made a sign for it that says "love shack"
(more images soon!)
- X 2
A mirror would send the light it in a single direction and polarize it. This is poor quality light.
Something that would scatter the light would be effective. Bright white glossy paper would do the trick.
If it's on the floor, will a bench next to it make it awkward to use either one? As in, I can't really get to the end of the bench without walking over the bed... From the pictures it looks to be 5-6 feet wide, the bench seems to occupy 2' in the renderings, leaving 3'-4' of floor space.
I have no idea how much a full pebble RMH weighs but driveway crushed rock generally weighs around 100-140lbs per cubic foot, will it need additional reinforcement?
- X 5
Could the bed be integrated into the pocket rocket system like a traditional Chinese "kang" system of stove/bed?
And from: http://www.hedon.info/BP29_Kang-LianzaoBedStove?bl=y
This reminds me of some vernacular thermally active surfaces that’s adopted by people in the rural part of northern China. Explained by Moe in his another writing, this design is called Chinese Kang, a thermally active bed. “In this system, the living space of the house was a few feet bove the level of the kitchen and fireplace in an adjacent room.” Hot air is channelled horizontally from the fire. There are slots built under the finished floor from the fireplace to and exterior chimney. The floor slab is made of concrete coated with clay. And on top of this are layers of oiled paper and floor mats. When heat warms up the concrete, the space above is heated up as well mainly due to radiant effect. the bed surface is then heated up as well and transfer heat to human body, mainly through conduction. Here, radiation is the main starting process of heat transfer, followed by more direct conduction. The following diagram explains this system.
I like the idea of doing a "loft" type bed that would take advantage of warm air being higher. People often don't realize how cold it can get on a mountain (or Montana Valley) evening in the summer.
I do like the look of it all, and how easily it went up.
As for design: do NOT put it the heat chamber above anything other than an insulating base (refractory cement/vermiculite mix or somesuch) because it will leech out alot of the heat and radiate it away from the bed -- namely, the ground, or air if it's the cabin above.
For even more efficient heat transfer, either a set of finned ducts (internally and externally would be ideal) or smaller-diameter tubing embedded in the thermal mass is best (think boiler or radiator design--or, even easier to visualize: I'm floor radiant heating). If the ducts are too large, you lose a great deal of surface area through which the heat can conduct, and out the chimney the heat goes.
That cabin is kinda scary, too: I see so much daylight thru the cracks, air intrusion would render the heating moot.
A simple charcoal burner would be a sweet little project for your LAB site. Charcoal burns hot, clean and over a reasonable time periood. Something like the KANG clay stove is constructed with the space for a pot molded into it so no smoke exits above the burn.
As for a bed. Is a Murphy style a possibility? Maybe as 2 "twins" side by side. A fold down table can be added to the underside of one bed. The bed itself acts as daytime insulation.
Would a vertical thermal mass be possible. Others have commented about the load problems associated with mass. If the chimney cavity runs thru some concrete blocks (laying the blocks on a slope) and the unused air spaces are filled with something that will hold heat - say sand - you'd only need a 3 foot vertical by 6 foot or 8 foot length to store the heat you'd need.
I like the idea of a fold down bed at the far end with a fold down table underneath. With the heat from the baseboard mass underneath it should be comfy warm.
- X 2
Well, what bumped straight away in my head, is hypocaust.
Cover the actual floor with sheet metal. Insert a 4 incher rocket so the feed is flush with the future floor. Or a smidge above. (that's where Cindy should bump in, as their 4 incher proved to be better than the other ones, well Peter van den Berg, has proved to be, onto which Cyndy's rockets are based)
Raise the floor 1 bricks width, making a surounding with bricks laid on their sides, and a few in the middle for supporting the future floor, direct the exhaust from the barrel into this space, cover the space with sheet metal, riveted and sealed with high temp silicon caulking. Cover the metal with pavers of some kind. Previous thinking will have to be done, as the suporting bricks should be on the corners of each paver. Drill a hole for the flue pipe in the sheet metal and pavers.
Otherwise, sam's design could be also done. I just had a crazy solution on hand.
ps. I'm a little new to this concept :S
Aaron Emberson wrote:Thank you thank you thank you! I'm in the process of building a tiny house right now and have been contemplating whether it's feasible to use a RMH! I have been also trying to integrate this as a passive solar heating thermal mass! I've done the winter sun calculations (nanaimo, BC) and it's looking very possible!
ps. I'm a little new to this concept :S
I would think it has just been the past two weeks that the act of cooking in a well insulated tiny house would not have provided enough heat and since last wed. the temperature has gone up again. (I'm just up the coast) Are you looking to build under the 103sqft? or putting it on wheels? to get past code. Or just far enough off the beaten path? (don't say where exactly ) If you really want something that uses even the heat from a 6inch RMH then under floor with insulation under that is what makes sense.
Aaron Emberson wrote:I guess you're right! maybe I'm being a bit over prepared! haha It will be on wheels and maybe that's why? taking it to whistler for a ski strip might need a bit more powah! I've been thinking that maybe a water tank for thermal mass would work best? then it could be drained when I want to hit the road again... but.. water brings a whole new element of over heating the thermal mass I would think? uncharted territory for me!
I know in our part of the world water is considered endless, but I don't know about sending perfectly good water down the drain every time I moved. Maybe you are not thinking about moving that often and so that is not a problem. Your tiny house has become an RV and you need to make sure it does not attract the wrong kind of attention on the road. You need to take extra care to make sure everything will stay attached when being moved over a wheeled house that will be moved once from building site to living site... probably at slow speed. You would need to be careful where you dump the water if it is frozen outside as you might leave an ice slick that could be dangerous to others. RVs often carry water (new and used) for some distance, but they do so with the water down low. You would want it higher up to be inside your living space, but still as low as practical as you may need to move with the water intact at least to a dumping site. For portable use you may also need to bring drinking water... water hookups via hose when it is frozen outside would be problematical... this is something to watch out for even in a more permanent location. The porta-cabin above gets around this by not using any water as the occupants are expected to use group bathing and eating facilities.
Water as mass could be fine. It should be smaller than cob or brick because it stores more heat. It also wants to be smaller because you are (even at Whistler) in a warmer part of the country. The water should not be capped or pressurized and the heated part of the loop needs to be level and designed so that no steam pockets are formed... In a small scale unit like you want, it may be best to heat the tank directly rather than running a coil through the flue gas. You would also want to design your water holding mass to be able to be frozen without breaking... air space on top and sides that slope out towards the top. You may never intend it to freeze, but life happens.
I've been thinking about insulating a very very small area so it could be heated very simply without fossil fuels.. perhaps electricity (battery bank and solar panels?) would be the best solution?
Aaron Emberson wrote:good points! I've always found myself to be a bit nomadic.. Perhaps that's why I've focused on the transportation factor. I've been contemplating sizing down even more then this for more ease of heating/transportation/and general cost. But the main issue I keep coming back to is heating! for instance.. could i heat the cap/cover of a truck with a renewable heat source without having a large cost? would a mini pocket rocket work? is there even a possibility of a functional thermal mass in a space that small?
I've been thinking about insulating a very very small area so it could be heated very simply without fossil fuels.. perhaps electricity (battery bank and solar panels?) would be the best solution?
Look in your local used boating store for a diesel fire place/heater. Use veg oil ...
The problem with a small space is clearance. So high mass makes sense. Need something with a small flame. Like a 3 or 4 inch rocket _stove_ put a big stock pot (12 in diam. by 18in. high) of water on top. Vent both the rocket stove and the pot outside to keep moisture build up down (it will be enough of a problem with you breathing already). A smaller pot of tin may work if it is sealed. get it up to melting point and put a blanket around it to keep it from leaking heat too fast.
I lived in a van for my first two months here, but I had power (free) and a heater. I found vehicles are not insulated very well but I got by fine.
Boilers have been pretty reliable for many years now. Good design and fab go a long way to eliminating leak problems.
> legionaires disease...
Very temperature and flow dependent. Or just temperature in the case of a heat mass. Probably have to design assuming a toxic mix. Since the mass would not be used for domestic purposes and would vent outside w/minimal air exchange it could be include optional germicides like chlorine bleach. Legionaire's has less history (than boilers) but if the mass were sealed to the living space and vented out it would be much less problematic. Vents can be sized and shaped to reduce air currents.
> maintaining water level in an open mass...
A sight glass could be incorporated into the vent and the vent could also be used to top off the tank/mass. With minimal air exchange through the vent there might be very little water lost. Die or food coloring in the water mass would help ensure an unambiguous reading of the sight glass.
But for sure, with a vented mass there would always be a critical need of some basic knowledge and regular maintenance.
- X 3
- Regarding the original diagram:
- Clearances to combustibles seem a little tight; I would allow more space especially around the barrel.
- Are the upward-pointing T's for cleanouts? I would locate them closer to the ends of the bench; it's easy to reach down a long pipe from a corner cleanout, hard to manipulate obstructions at corners from a long pipe away.
The most important place to access with a cleanout is the manifold under the barrel, followed by the exit chimney, then the 180-degree bend.
- I agree about including insulation on floor and walls of this structure, especially if the undercarriage may remain exposed to cross-breezes. Trying to heat the current, slab-walled structure will result in a heater that is massive overkill once the insulation is in place.
- For general portable housing, I agree that good insulation is a better investment than thermal mass heating - for the general case.
Mass = heavy loads to transport, whereas insulation is usually very lightweight, and allows you to cut heating loads by large factors.
(e.g. R-30 insulation compared with an R-5 non-insulated wall means 1/6 the heating load, but usually only a few % more weight - maybe 10 to 100 lbs for a 500-1000 lb trailer structure).
Similarly, our ancestors used canopy beds, cupboard beds, down and woolen insulative comforters and clothing to reduce the indoor temperatures needed for health and comfort. Any reduction in comfortable indoor temperatures reduces heating loads by quite a lot.
For a cabin of this size, a cupboard-bed in one end with double insulation might prove easier to keep warm overnight than the best stove setup.
I will assume that we are designing for a technically 'portable' shelter, but one which may be occupied in extreme cold for long enough, or often enough, to make efficient heating worth the investment.
Issues with INSULATION:
- Withstand vibration & warping effects of travel (insulation boards or batts rather than loose-fill which may settle badly; fiber-based wall coverings like wood panelling or fabric, rather than brittle materials like cement stucco or plasters.)
- Maintain minimum air flow for interior habitability: about 1/3 of the buildings air volume per hour. Campers without good ventilation are subject to major mold problems.
- Manage vapor-barriers, if used, so that both indoor and outdoor humidity cannot cause condensation problems within walls.
Campers will experience more different climates than stationary homes, and more fluctuations of indoor humidity due to sporadic occupation.
(Condensation happens when moisture or moist warm air meets a cold, impermeable surface. Dew forms on the cold surface and runs downward into whatever pockets. Wall fittings such as electrical outlets, where insulation is thin, can be bad spots for encouraging condensation. Solutions include using permeable or fibrous materials instead of non-permeable vapor barriers, to breathe and wick away water (wood, cloth, or leather instead of vinyl); never placing double vapor barriers on two sides the same wall; and trying to separate any cold surfaces from air flow using insulative non-permeable materials, such as closed-cell pour foam.)
- Since I'm going into difficulties in detail below, worth noting that ALL mass-heater channels that are not double-lined with permanent masonry must be VERY CAREFULLY sealed, and should be monitored for CO or smoke leaks.
Portable mass heaters will endure road vibration, extreme "settling", and other forces not normally considered in the design of masonry-heater-type appliances.
- Regarding removable mass for transport:
Water is attractive for its thermal capacity and general availability at most campsites (we don't stay anywhere long without it), but all the problems mentioned above are real. To summarize:
- Steam evaporation (cooling, plus indoor moisture / mold potential);
- boiling (the above plus explosive potential). Explosion hazard increases with any system that depends on full tanks, pumps, thermosiphons, or monitoring devices to prevent overheating; redundant safety measures are essential.
- freezing (expansion and damage to tanks / pipes / fittings);
- disease (many diseases thrive in stagnant water. Legionella is an unusual bacteria that thrives in warmer-than-lukewarm water, and causes disease through aspiration (breathing it in the shower); when the water is not sprayed, the legionella rarely causes health problems. There are all manner of other bacteria and microbes that will breed at almost any temperature right up to boiling; not all germs cause disease, but even the innocent ones can cause weird odors and gluck buildup.).
- strain, load, and balance issues if the structure is ever hauled with full tanks, or if tanks are imbalanced during hauling.
Other dangers not mentioned include
- scalding (water/ surfaces over 120 F, any splashing during transport if people are inside; and especially scalding and hot moisture buildup around steam leaks);
- corrosion (non-pressurized systems that are less likely to explode, are more likely to contain oxygen that can accelerate both corrosion and "gluck" buildup from aquatic life);
- likelihood of leaks and damage from road vibration and debris, structural flexing, and so on.
- Scale buildup is a problem for most plumbing, but may be more so in a heated and cooled tank using non-potable water.
- Overheating: Water tanks imply a variable thermal mass, and therefore variable load on the heater. Any heater that uses water as a thermal mass should be configured to operate safely when empty, as well.
Let's be very clear, that no matter what kind of water is put into a mass-heater system, the result will be non-potable water under all likely conditions of use and maintenance.
All of the above are problems that can be dealt with, quite successfully by modern engineering. Indeed, warm water was a resource used successfully by our ancestors in cooking, washing, and geothermal baths.
But they make using water as thermal mass a sight more complicated than insulation. Water is a very dense material, with great heat capacity (anything better, like solid metals, tends to be far more costly). Plus it's non-toxic, non-polluting for discharge (the occasional ice or rust patch notwithstanding), and available at all suitable campsites.
The simplest and most easily-maintained method might involve separate, liftable water units like pots, buckets, or old-fashioned milk jugs, with a cookpot-type lid (loose enough to vent steam, but tight enough to prevent undue evaporative loss). This has been used to their satisfaction by woodstove owners elsewhere on these forums.
Whether the containers should be metal or plastic depends on the temperatures involved, and whether corrosion, vibration, or heat is the limiting factor for container lifespan. To limit carrying distance, one container or a drainage pan under the whole thing (to catch leaks and splashes) could be hooked up to an exterior drain tap.
If you have the skills to cushion your plumbing from all of the problems mentioned above, then one or two tanks with an outside drain might also be practical.
MINERAL / OTHER MASS:
- Other removable mass options: dirt, sand, rocks, gravel. Essentially, any mineral mass you may find on site, and which can be reasonably expected at future sites. More suitable for long-term occupancy of a site, with rare and relatively slow towing. Not super-likely to be on hand at trailer parks, but if you are moving to any site permanent enough to consider trenching in some water pipes or electrical, loose dirt is likely to be available.
- the possibility of introducing soil biota that want to eat your structure (ants, termites, fungi), or other undesirable contamination (soils that offgass something when heated?); and of transporting the same between sites.
- a somewhat messy loading and unloading process, which undeniably involves "work"
- reduced thermal storage effectiveness (compared with solid or water mass) due to thermal mass being lower, and conduction reduced in favor of insulation effects of air pockets in any granular mass.
If you are planning to re-use the same gravel in a new location, the benefits of being able to remove it for travel are negligible, as it's the energy required to transport that mass that is a problem in the first place. If you are planning on hauling the whole load around anyway, consider upgrading to a smaller amount of dense materials such as masonry, clay or ceramics, or water units.
- Regarding a rocket as overpowered for a particular space:
6" rocket heaters are routinely used in spaces under 100 square feet. The "rocket" part of the name does not imply any special excess of fuel, but rather a tendency to burn clean with good draft and a "whooshing" sound.
Regarding 4" and smaller rocket heaters: Cookstoves are commonly (and relatively successfully) made to this size; we've worked with 3" and 4" cookstoves that put out huge amounts of heat for hours at a time.
A 4" J-tube heater core can be used to power a radiant heating firebox; and potentially for short, mostly-vertical runs of heat-exchange pipes. The problems we've seen come from trying to extend the length of 4" pipe to heat a similar thermal mass to a 6" or 8" system, without realizing that the extra surface area and reduced diameter of the 4" pipes creates a LOT more drag on the system. Most 4" heaters don't have enough "push" to overcome much length of drag, so the heater works more like a woodstove (quick-response radiant heat) than a masonry stove or mass heater.
There are small masonry stoves and soapstone stoves that also split the difference, giving clean-ish fire and long-ish heat storage compared with small woodstoves.
- Regarding the heat of cooking as sufficient to warm a well-insulated space:
Absolutely. If the cabin is a sleepout associated with a central camp kitchen, then a good insulated sleeping area / bed, and a heat-giving lamp such as kerosene, or electrical (incandescent or IR lamp), could be more than sufficient.
If the cabin is stand-alone quarters for someone wintering over, perhaps as a site caretaker in a remote corner of a property, or as a getaway cabin for an owner who is still working in the city to pay off a new land purchase, then cooking and/or heating facilities might be important.
A rocket heater's barrel doubles as a reasonable cookstove / coffee stove, and can be fitted with an oven or stockpot on top (stockpot full of water = thermal storage, plus normal washing and cooking functions).
A small cookstove might also do the job, but without the benefit of overnight heat from (non-burning) mass.
Regarding fire danger:
Burning a woodstove or cookstove all night, or a rocket heater during the day - I think the fire danger would be greater with the woodstove, assuming the rocket heater was constructed with reasonable care.
There are safer, virtually fireproof space heaters, but the ones I know rely on fossil fuels or on-grid power that may not always be accessible in the camping locations that a mini-house adventurer might enjoy.
- I assume that a portable dwelling would be occupied only at rest, and that we do not need to heat it while in motion, nor protect occupants from the dangers of motion + heat e.g. scalding water splashing about.
If there is any intention to have people live in it while underway (as in many types of boat), then I'd look into boat-type heaters and good insulation.
Boats often use a small diesel or propane space-heater, to reduce hazards from tipping or shifting during travel. Cookstoves may be diesel, wood, or gas fired; for most cruisers and fishing boats, the cookstoves (and many lamps) are mounted on gimbals. Electrical heaters are not typically used except on luxury boats, as the electricity has to be generated or collected from solar on board, and heat takes a lot of energy. If you're going to run a diesel generator to power your heaters, you might as well run a diesel heater with fewer losses. If your boat is going to depend on dockside power for successful cooking, it's basically a dock not a boat.
All of these marine solutions tend to be more expensive than a comparable heat-output device for stationary dwellings. They may use stainless steel (corrosion resistant), specialized exhaust protection from waves, and other features that a camper doesn't need. But they're worth investigating for inspiration.
That's my thoughts so far.
Rather than a rocket mass heater, I am now thinking that it would be nice to try out heating it with a single light bulb.
The whole "porta cabin" idea is something I came up with ten years ago. In fact, we dug up some of my drawings from back then just before we started building. Nothing too earth shattering: just a little house on skids. Back then I was building everything on skids.
The love shack how has a window, insulation, inner siding and a bunkbed.
The door is getting an upgrade and then we're going to move it up the hill a bit. Where a trail was built yesterday:
In the next few days, it will get a couple of solar panels, a couple of batteries and an inverter.
We've hit a bump in the road in getting it moved up on the hill. The road that goes up there has a steep spot. It could be a great test for the new electric tractor.
I'm THIS CLOSE to ruling the world! Right after reading this tiny ad:
2018 Peasant Permaculture Design Course in Montanahttps://permies.com/wiki/74473/permaculture-projects/Peasant-Permaculture-Design-Montana