I'm trying to set up a safe heater for an 8'x20' cabin. The cabin is based on a standard steel container. I want one that doesn't require electric, and exhausts any fumes to the outside. I'm in the process of insulating at R9. This is in Missouri to give you an idea of the temperatures involved. It was 16F this morning, but I probably wouldn't be using the cabin if it were much colder.

I have access to a wood stove, but that's really too big and hot. I have a catalytic heater, but that requires leaving a window open because of the use of oxygen.

An ideal soluton, if I could find it, would be a very small kerosene heater that would install on one wall, or better yet, like a window air conditioning unit. The heat would go inside, but the fumes outside. I haven't yet seen anything like that. I have seen a larger kerosene heater in an old Maine house that sat on the floor and exhausted through the wall, so a smaller, wall-mounted version of that is what I'm envisioning.

I want to avoid fire hazards and fumes. It could be kerosene, or some alternative.

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    Is gas or propane an option? – ThreePhaseEel Oct 29 '17 at 21:25
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    @threephaseeel I'd consider propane. I could run it off a 20lb tank sitting outside. Gas would be fine, too. – Don Branson Oct 29 '17 at 21:28
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    homedepot.com/p/… – Mark Oct 29 '17 at 22:02
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    The keyword you should look for is "sealed combustion" or "direct vent"- a heater which has an intake and exhaust path for the combustion air/fumes that is totally separate from the inside air. One of the more common variants of that sort of heater is also one of the least expensive for fuel - a pellet stove (you'd want a small one) but most of those do need electricity (a few don't) – Ecnerwal Oct 29 '17 at 22:58
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    @dandavis depends on your definition of "room". Most people running kero heaters are doing them in very drafty places, where there's lots of removal of combustion products and fresh air rolling in. Containers are much too tight. – Harper - Reinstate Monica Oct 30 '17 at 14:47

There's an absolutely fantastic heater called a wall furnace. It is a proper furnace that mounts in a wall, and is either one-sided or two-sided. You could mount a 2-sided unit on an interior joist wall. Or you could mount a 1-sided unit on an exterior wall by spacing it out from the wall 4", this would let you put a jog in the stack pipe and penetrate the wall instead of the roof. (I hate roof pens, especially on containers which have irregular roofs).

A slight variation is the floor furnace which mounts below the floor in a grating.

They typically are sized for 25,000 to 50,000 BTU and intended to heat an entire, modest sized California or Florida home of 500-1200sf (depending on how well insulated it is).

They use a millivolt thermostat, which means a thermopile (Peltier device) right on top of the pilot light, creating just enough power to operate the propane solenoid valve. The pilot must run 24x7. They come set up for methane, but can be jetted for propane.

Exhaust is straight up, via convection. Most are not "direct vent" and rely on some draft in the building to fuel them. Keep in mind there is no electricity to force air through the combustion chamber, so the airflow can't be too convoluted.

You cannot find these in the snowbelt. This is absolutely daft, because the furnaces they do have in the snowbelt all absolutely need AC power, and AC power fails a lot during the winter, often for days at a time. I would want one of these at least as a backup. It would also make a wonderful auxiliary heat for a heat pump system.

Combined with a modest but carefully designed DC battery/solar system, you could be toasty warm and watching Netflix while your neighbors are futzing with generators.


Adding to @Harpers writing, there are many heaters you could use. You could "GOOGLE" (direct vent gravity wall furnaces) for sealed combustion heaters that need no electricity, and do not use the air in the room for combustion or non-sealed combustion that uses room air for combustion. Some can be bought to use either natural gas or propane. They come for use with electricity or without electricity. Some standard brands are; Cozy heating systems,Empire, Williams and one I never heard of, House Warmer. Any of these would solve your heating problem and can usually be bought locally or shipped to you. Myself, I prefer the sealed combustion type heaters

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