Tiny Home Heating Options Part 2
Part 2: Non-Electric Options
If you haven't already read Part 1 of this post, you can start here.
Electric heaters are usually only practical on-grid, with continuous use of a generator, or with a truly enormous solar array. For off-grid tiny living, direct use of fuel for heating is often more practical than using it to drive a generator. Some of these options also offer ambiance that you can't get with an electric heat source.
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Propane Heating Systems
Propane is a popular choice for both mobile and stationary homes. Propane is readily available for purchase in refillable propane cylinders, or it can be delivered to larger above-ground or buried tanks. Many homes already use propane to fuel a stove or range, or a propane fueled absorption refrigerator, so using it for heat as well is an easy choice.
Forced Air Propane Furnace
Propane fired forced air RV furnaces are popular standard equipment for RVs, and they can work in tiny houses too. Tiny houses are larger than RVs, but they're typically better insulated, so RV furnaces are worth exploring for tiny homes. Typically a furnace uses a 12 volt DC fan to force air through ducting, and distribute it throughout the space.
Some RVs or tiny houses with under-floor water tanks have a furnace vent and return in the tank area to keep fresh and waste water liquid in freezing conditions. It's important to have both a vent and return in an area if you want hot air to circulate from the furnace.
Furnaces are generally fairly loud, and tend to consume a lot of DC power to run the fan. If you're using a furnace to heat your home off-grid, it helps to have plenty of solar to keep your house battery topped up.
Hydronic Heating Systems
Some newer RVs are now coming standard with hydronic radiant heat systems. Companies like ALDE and PrecisionTemp offer systems that can provide both domestic hot water, and a separate glycol loop feeding radiators throughout your space. Hydronic heaters typically run on propane with an additional electric heating element for use when shore power is available.
Hydronic heating systems are versatile solutions that can provide even heating throughout a space or spot heating in particular areas. We'll explore some of the details of distributing hydronic heat in part 3.
Propane catalytic heaters are a popular option for off-grid spaces. A catalytic heater uses a special surface to decompose propane into CO2, water vapor, and heat without any actual flame. They provide radiant heat very similar to electric infrared heaters.
Since catalytic heaters feed from and exhaust to the living space, they can have big impacts on indoor air quality if misused. Water vapor is one of the decomposition products of propane, so catalytic heaters can cause problematic humidity build-up and condensation inside the living space. Worse, but less common, catalytic heaters can potentially use up all the oxygen in the room and create a hypoxic environment.
If you think you'll notice when you start to run out of oxygen, watch this Youtube video on hypoxia, and you'll understand why hypoxia is so dangerous. There is no feeling of suffocation with hypoxia—that feeling you get when you hold your breath is from the build-up of carbon dioxide in your blood, not from lack of oxygen. A person in a hypoxic environment quickly becomes too confused to realize what's happening. If you use a catalytic heater in a small space, it's critical that the space is well ventilated, and an oxygen sensor is a good idea.
The catalyst surface needs to be kept clean to work, so catalytic heaters should be covered when not in use.
If you like the idea of a catalytic heater, but want to avoid oxygen and moisture problems, you can go with a vented catalytic heater. A vented catalytic heater works the same as a standard one, but it uses a fan to vent the combustion gasses outside, so water vapor is removed and oxygen is replenished with outside air.
Direct Vent Propane Burners
Non-vented propane burners are available for indoor use in both freestanding and wall mount configurations. These burners don't require any electricity, but they have the same problems associated with catalytic heaters since they both feed from and exhaust into the room air. A better option for a tiny home is a direct vent propane burner.
Wall mounted direct vent propane burners are self-contained units that typically require no electricity, and vent all combustion gases through the wall behind them. The Williams Direct Vent Furnace is sold for natural gas, but can be converted to propane with an optional kit. It includes a thermostat, which is a basic feature that surprisingly few propane burners offer. This Martin Direct Vent Wall Furnace also has a built-in thermostat, and it has a ceramic viewing window so the fire is visible while the heater is running.
Dickinson Marine Newport P12000 direct vent propane fireplace is a lightweight wall-mounted design that has a visible flame, which can add to the ambiance of the room. Since it's propane fired, the Dickinson Marine propane fireplace will continue heating your space as long as you have propane in the tank. Unfortunately, there's no thermostat, so you can only select between "low" and "high."
Another option for a small direct vent gas stove is the Mini Franklin gas stove. Its 8,000 BTU/hour rating might not be enough for primary heat in most tiny homes, but it would make a nice addition to a room for supplemental heat and ambiance.
The Jotul GF 305 is a more serious direct vent gas fireplace option in the 18,000 to 28,000 BTU range. With a free-standing cast iron body and a large fire viewing window, the GF 305 could make a nice focal point for a living area with a design similar to a wood stove, but with the convenience of gas heat.
Small Wood Stoves
Small solid fuel stoves (wood or coal) provide wonderful warm, dry heat, and create ambiance that can completely transform the feel of a space. They require zero electricity to function, can be used for cooking as well as heating, and use a readily available renewable fuel source. Since wood heat is becoming more popular in the tiny living community, small stove choices and install parts are becoming more abundant and easy to obtain.
Salamander Stoves now has USA distributors for the British designed Hobbit Stove (shown in the title photo) and the smaller potbelly-style Pipsqueak. Tiny Wood Stove based in Hayden, ID and founded by Nick Peterson (of LivinLightly fame) distributes their own Dwarf Stoves in three sizes, along with solid fuel install kits for tiny houses and RVs. Cubic Mini stoves from Canada makes the small Grizzly and even smaller Cub stoves, and sells some 3" double-wall pipe that fits their stoves, though you have to source all your other flue parts elsewhere. Navigator Stove Works hand-builds their enameled marine stoves to order in Orcas Island, WA, and will provide installation parts, but only for their own stoves. Dickinson Marine out of BC, Canada has a solid fuel version of their Newport stove available. Fatsco Stoves from Mesick, MI makes the miniature potbelly style Tiny Tot and Pet stoves.
I'd be remiss not to mention the futuristic looking and heavily marketed Kimberly wood stove. The sell price of the stove is way out of line with their competitors, and they have a page of rationale here. I'll leave it to the reader to check their math.
Some larger stove options like the Hi-Flame Shetland, the Morso Squirrel, and the Jotul F 602 are pushing the limit of practical size for a tiny house, but can work well for larger spaces and colder climates. Antique potbelly stoves can sometimes be used in small spaces, but they're often too big for the space.
Aside from safety, the most important consideration in installing a wood stove is to match the stove's heat output to the needs of your space and lifestyle. Wood stove output can only be controlled within a certain range. Too large a stove, and it's difficult to run your stove efficiently without overheating your space. You can under-fire or choke down a larger stove to some extent, but burning cool or choked fires causes creosote build-up in the flue, which can lead to a chimney fire. It's best to select the smallest stove that can adequately heat your space, and burn it hot and efficiently.
Some wood stoves have options for using outside air for combustion rather than air from inside the living space. If a stove is consuming inside air, it can create cold drafts around windows and doors where the combustion air is being replaced with outside air. Connecting a stove directly to outside air can be helpful where a space is too airtight for the stove to properly draft from inside air. But exchanging outside air is good for indoor air quality, so you may be better off having the stove exchange air. We'll discuss indoor air quality strategies further in part 3.
Some small wood stoves have water boiler options, which can be connected to a hydronic heating system. If your stove doesn't have that option available, you may be able to use a commercially available flue water jacket, or just wrap a coil around your stovepipe or the stove itself. You should use glycol in the hydronic loop to prevent freeze damage, and you need a pressure relief valve for safety. We'll discuss hydronic heating systems further in part 3.
The smaller a wood stove is, the more frequently it requires stoking. Wood stoves sized for tiny houses are typically too small to keep burning for an entire night without any stoking. If a small wood stove is your only heat source in a cold climate, plan on waking up a couple of times a night to stoke the stove, or just sleep under some warm blankets and start the stove back up in the morning.
Many small wood stove models are also approved for burning coal. Coal burns relatively slowly and has very high BTU content, so it can be very helpful for longer overnight burns if coal is available in your area. Coal is a fossil fuel, so it's generally not as environmentally friendly as a renewable fuel source like wood.
Check if the area you'll be living has burn bans before deciding to use a solid fuel stove as your primary heat source. Densely populated areas and valleys where smoke tends to get trapped will sometimes have temporary burn bans, which could be a problem if your stove is your primary heat source.
Rocket mass heaters are a type of wood stove that can be a good option for heating a small cabin or off-grid space. A huge mass of soil or clay is used to soak up heat from the rocket stove's combustion gases, which provides long-lasting, efficient, even heating. Since the mass of the rocket mass heater usually weighs thousands of pounds, it's not a practical solution for any structure on wheels.
If you're considering a wood stove for a tiny space, check out Tiny Wood Stove's free guide to wood stoves for tiny spaces, which reviews all the considerations for sizing, sourcing, and installing a small wood stove in a tiny space.
Heaters using diesel fuel are available, which could be useful if you're already storing diesel fuel for use in a vehicle or a generator. Household diesel appliances usually use a day tank with a gravity feed supply line, but those mounted in vehicles often use pumped fuel from the vehicle's tank. Most diesel appliances can also run on bio-diesel or various kinds of waste oil. Diesel heater options could be ideal for preppers, since diesel is a versatile fuel that's easy to store in quantity. Downsides for diesel appliances include the odor, and the fact that diesel and oil can get viscous when it's cold, so you may need to heat your fuel before firing your heater.
Dickinson Marine makes a diesel variation of their Newport stove, as well as a marine diesel cookstove. Various floor mounted marine diesel heaters are available, some of which also have water coils for potable or hydronic heating.
For some tiny spaces, especially small vehicles with on-board diesel like Sprinters, a forced air diesel heater could be a good option. For smaller spaces and those located in warmer climates, the Espar Airtronic D2 for might be a good choice, with an output of 3,000 to 7,500 BTUs. For larger spaces, the Espar Airtronic D4 tops out at around 13,500 BTUs, the Airtronic D8LC at 27,000 BTUs, and the Airtronic V7S at 41,000 BTUs.
Passive Solar Heating Panels
While solar electricity is an inefficient method for powering a space heater, solar heat can be captured and directly used to heat a room. Package solar heating panels are available, but often surprisingly expensive. A more cost-effective approach might be to install a DIY system into the exterior wall of your tiny house while you're building.
Since passive solar only heats when the sun is shining, you'll want to have at least one additional heat source. But if implemented well, passive solar heat can significantly decrease your need for supplemental heat. You'll be able to heat your house with a smaller, cheaper secondary heating system, and use significantly less fuel or electricity to heat your home each Winter.
Liquid Fuel Space Heaters
Some liquid fuels are able to be burned inside since, like propane, they burn cleanly enough to produce only carbon dioxide, water vapor, and heat. The same warnings that apply to catalytic heaters also apply to these devices—since they feed from and exhaust to inside air, they can create a hypoxic environment, and even if properly ventilated can cause excessive buildup of moisture in the living space.
Some kerosene heaters are designed for use indoors. An attractive, though probably less practical heating option is a tabletop ethanol fire pit. As with any open flame, these heaters should not be burned unsupervised.