Rocket Mass Heater in a Camper

Hello all,

This is my first post and I have a question regarding installing a rocket mass heater in a camper. I am graduating college in May (at 34 years old no less) and will be moving into my recently purchased 36ft camper once I'm finished. My goal is to use the camper to reduce my consumption as well as my financial expenditures in order to pay off my mountain of student loan debt as quickly as possible. I do not want to rely on propane or electric forms of heat any more than is absolutely necessary. I love the idea of a rocket mass heater and believe that if I can make it work inside the camper, surviving winter inside it (with a short haired dog) will be not only plausible, but comfortable. I think it's important to note here that I live in Michigan and if you've been keeping tabs on the weather around the Great Lakes, you know it can get extremely cold here (-15F near Lansing this coming weekend). Creating the heater will be the easy part since I have been studying many designs for months. However, here are my concerns:

Weight: The camper already weighs more than 5500lbs. Some of the cobb thermal mass structures I've seen weigh in at 2 metric tonnes. How do I calculate how much mass I'll need, to efficiently store the energy I'll need, to heat this unit and keep it above 60 over night, all while keeping the weight down. (I don't want to have to purchase a larger truck than is already needed to pull the unit.

Heat reflection: I will need to reflect the heat generated by the barrel away from the camper walls to avoid damaging them as they are made from a wood-based paneling. I don't want to compromise the glue. Will a couple layers of aluminum flashing work?

Barrel size and ducting: I only want to utilize one barrel and combustion chamber, but want to be able to switch the heat from the living area to under the bed in the bedroom, can I insulate the duct work so the heat will be absorbed by the mass under the bed and not be lost in route?

Thank you all very much for lending your expertise,

Rusty

Whoa. I am NOT one of the RMH experts on this site. I am certain that they will chime in on this thread.
rMh. Rocket Mass heat.

There is a rocket stove heater that is used primarily for cooking, and there is a rocket mass heater, used primarily for heat.

For heating, the RMH is relying on the mass to retain the heat, and help keep the space warm, long after the fire is gone. The heat is collected in this mass, and slowly this heat is transferred into the living space, after the fire has died.

A huge part of the RMH is the "M" (Mass). It is this mass that makes it efficient for home heating. For a mobile unit, you will need to move this mass (pay for a lot more fuel) to keep its functionality alive.

In my estimation, a RMH is not a good choice if you need to buy extra fuel to move it from point A to point B.

Rusty Rich-
I have owned several large 5th wheel campers and if your 35ft camper weighs only 5500lbs I would be really surprised. My 2003 25ft 5th wheel weighs more than that. If your using a 1 ton Ford 7.3 powerstroke or 3500 Dodge cummins truck towing the additional weight would not be a problem. However I can see no way to put a thermal mass of cob in any camper even if it has a slide (which you couldn't close to travel if a RMH is installed) They are not designed to have that much of a cargo load capacity. You probably have an all season camper that has an insulated sub floor where the holding tanks are, but you still need to maintain a moderate temp in the camper to prevent freezing of the tanks/lines and drains.
You might be able to use a couple 55gal barrels of water for a thermal mass if positioned over a frame rail near the axles.
If I was you I might actually consider using a waste oil heater, or possibly a solar water heater for some of the time.
I'm currently contemplating using a pocket rocket as an immersion heater in a tank/barrel of water and circulating to 55gal barrels for thermal mass heat. As well as adding a heat exchanger system to heat my aquaponics fish tanks.

Actually if you can plugged in somewhere (like a campground where electric is included) you could use an infrared electric heater. I also had an RV that had a roof AC/heater combo which only used electricity.

Hey Rusty,

Water is an incredibly effective "mass" for storing heat. It comes with a host of problems when so used... but still. If you use water tanks to contain your mass you could drain them for transporting the trailer then refill them for for use while you are parked and living in it. Just an idea. I'm sure you'll hear from the "safety wardens" on this one.

Tom Strode wrote:Hey Rusty,

Water is an incredibly effective "mass" for storing heat. It comes with a host of problems when so used... but still. If you use water tanks to contain your mass you could drain them for transporting the trailer then refill them for for use while you are parked and living in it.

This is exactly what I was thinking. Another aspect to consider is the balance of weight. The trailer was designed to be stable when towed. If you throw a few thousand pounds in random locations you might find yourself in a "tail wags dog" situation.

Are you sure the trailer was built "winterized"? Most aren't, and the water and waste tanks are often exposed to the weather.

Thank you for the prompt responses and the insight. I have absolutely considered the weight and balance issue. In fact, that's really the bottom line of what I'm trying to solve. I really do like the water and could possibly incorporate that into a hot water system. I'm still toying around with other ideas for heating the camper such as solar collectors and wood burning stoves. My main goal here is safety. With that being said, adding a few thousand pounds to the camper isn't an option unless I can remove it before hitting the road. That's why I am looking for a dry substance that holds heat well, but doesn't weigh much so I don't have to use any more water than I have to. I've spoken to a few chem majors and hope to meet with a chem professor today to see if such a substance exists, in mass quantity, at a very low cost. Worst case scenario is I'll have to get an additional solar panel and a few extra batteries to run an electric heater at night. Tom, I just purchased the camper a few weeks ago and parked it on the farm I am leasing. My university is 300 miles away from there so I haven't had a chance to really get into the guts of the unit but I highly doubt it is insulated to any extent. I have some ideas for that as well and now that you've got me talking about it, I think that's the issue I should be addressing first so thank you for that.

Light dry substances are called insulators. If you can find one that holds heat well, in mass quantity's, for a very low cost we all want to hear about it.

Insulation is your best bet. Stopping air infiltration is a biggie too. You don't want it too tight but if you block everything except what you let in, then heat that... Look at Bernhard Masterson's case study in the book. That small a space, well insulated, you may not need much more than body heat.

I camped out here (KY) during the winter while I was putting up the bldg. and I found that sweaters during the day (actually a down vest keeps your core temperature up without restricting arm movement) and taking a hot brick or two to bed with you (well wrapped in towels or blankets) at night can go a long way towards keeping you comfortable.

I tried a "space age" spray-on insulation on my metal bldg. Some ceramic like they use on the space shuttle, powdered, and mixed in epoxy. Big hype, but I couldn't tell that it did a thing. Then I glued up a foil-foam-foil on the inside, and taped the seams with that metallic duct tape, to match the foil. And, that worked way better, at under half the cost. Maybe because it did a much better job of blocking air infiltration. They make a foil-bubble-foil that's more common, but I was worried that the bubbles would deflate over time. Anyway, that stuff's thin so it wouldn't take up much of your limited space and I think you'd find it well worth the investment.

hi i have lived in a 40 coach for the last 14 years over that time i have done fair bit to keep warm. i live in a pretty warm area surrounded by the sea so it doesn't get too cold. i have used a wood stove for years but the last 2 years i have used a waste oil burner based on the design by spike. mine is a basic as it gets. 8 inch cast iron pot with 5 inch cast flue pipe 6 inches long welded to the lid. i just have a about 6 foot of flexy stainless flue stuck in the top of it. it has a needle valve and a tin can that supplies the fuel. waste oil diesel or kero. works a treat and is safe as long as you don't overfill it.
i don't know how your trailer is constructed but if it is like a caravan the insulation wont be much. i used 4 inch celotex under the floor and on the walls, and that stuff made from plastic bottles in the roof spaces.

i lived in the east of the uk before in a converted van. that by UK standards
was cold. i used plasterboard and fibreglass on that. i dont recommend that if you are driving as it will all end up in the bottom of the walls. use celotex instead.

Rusty-
Since you live in Michigan your camper might be more likely to have an insulated "basement". If when you look under the camper and you don't see exposed tanks (sewer drain outlet will still be exposed) then you're OK. If it's all exposed then either you'll need to put skirting all around it to seal up the under side (like a mobile home) or you won't be able to use the plumbing in the camper as it will freeze and break the tanks. I've had both kinds of campers and much prefer the "all season" models. My current one is not which kills the deer hunting trips lately.
Well a totally off the wall thought just occurred to me that you could maybe build the RMH under the camper (with insulated skirting) and heat the floor and the camper.

thats not too far off the wall. i have had the same thought. my bus has around 3 feet between the ground and the floor. i have thought i could remove the insulation from one area and build the mass under that part. i would lose insulation when the heater was not running ,but that shouldn't be a problem. be easier than reinforcing the floor to take the weight. bet the mice and rats would love it. hopefully so will the cats.!!!

Rusty,

One important question is whether you intend to be able to move the camper around or if it will be kept in one place?

Also, I don't think you could possibly generate enough solar power on top of your camper in Michigan in winter to keep yourself warm with electric heat.

to generate enough heat to keep ypu warm in a cold place would take a heck of a lot of panels. just some figures off the top of my head, apologies if they are not accurate. a good panel wil produce 15% total solar isolation is around 1000 watts per sq metre in winter that will drop to 150 200 watts or so. panel wil produce 15% of that 25/30 watts per square meter you need around 3 kw to keep warm. thats 100 panels at 1x1.5 meters ech you see where this is going? as i say the figures are off the top of my head so may be out a bit. silent genny would be cheaper and easier.