Heating a Tiny House: Wood Stoves
When choosing wood heat for your tiny house, details such as the output of the stove, the source of intake air and the type of wood you burn become critical concerns.
One of the great benefits of a tiny house is that you should have a modest heating and/or cooling bill. Unless you're a real comfort wimp, I suggest yout choose one advanced system or --heating or cooling--and use a low-tech solution for the other (off season) In this first in a series of articles on heating/coooling, I'm going to quickly run through the pros and cons of various options, starting with wood. For our prototype tiny house, I've chosen a 280 sq. ft. living space.
Wood stoves are inexpensive to operate (if messy), and throw off a tremendous amount of steady btus, so much heat, in fact, that you want to be careful not to overpower your space. A typical recommendation is that a well insulated 1,300-sq. ft. home can be heated with a 42,000 btu wood stove. Extrapolate that down to 280 sq. ft. and you're looking at a heating requirement of just 9,046 btu.
Petite Heater. Designed for shipboard use, the Navigator Sardine can provide the modest wood heat needed in a tiny house, but it will require special wood sizes and a custom direct air source.
Fortunately, there are at least a couple of small, nice looking woodstoves that fall into this range, including the Navigator Sardine (7,500-18,000 btu), the Shipmate Skippy (9,000 – 28,000 btu). One thing I like about both of thes stoves (which were designed for nautical use) is that they have built in flat top burners for cooking.
Air to Burn
One problem with both of these stoves, however, is that they do not have a built-in intake for fresh air. If your tiny house is tightly built, wood stoves can literally suck the air out of the room very quickly. Open a window and you not only let cold air in, you risk creating a "loop" with the stove that pulls in pollutants from the stovepipe.
One solution is to provide your own makeup air system, which can be as simple as an insulated pipe to the outside. The only relatively small stove I could find that has a built-in direct air option is The Hobbit by Salamander Stoves, but it's rated at 14,000 btu. That's a lot of firepower for a tiny space, and you'd have to burn it very conservatively.
Tiny Stove=Tiny Wood
One drawback to the tiny stoves above is that you're getting into custom log sizes, which means you can't just buy a cord of seasoned wood from your local forester. You'll have to either cut your own or order a special, shorter length. The Navigator, for example, takes logs that are 6 inches long, split to under 3" widths. Even the larger Hobbit won't take a standard 16-inch log.
One option for "slowing down" the heat is to burn woods that are lower in btu output, such as oak or spruce. You may be aware that certain softwoods such as spruce can create a lot of creosote problems. That's just one reason why buying a modern, EPA-certified stove with built-in catalytic converter is important.
Wood Smoke is Not Quaint
There's a reason a lot of areas have now banned those outdoor, standalone wood stoves. Wood burning produces a LOT of airborne particulates--bad stuff for the lungs, especially for children. Don't even think about putting an old woodstove into your new tiny house. The difference between an old wood burner with no catalytic converter and a new EPA-certified model is huge. Modern stoves produce less than half the particulates per hour as their predecessors. These stoves combust the smoke twice, essentially burning up most of the creosote that will otherwise clog up your stovepipe. That doesn't mean they are clean-burning, when compared with other fuels, but they're a big step up. The key is to keep those emissions away from living and working areas, which means you'll have to be aware of local micro-climates and wind patterns. So burning wood in a tiny house begins a the earliest design stage. You'll also want the height of the stovepipe to match the conditions (not to mention the local building/fire code).
So should you burn wood in your tiny house? Wood, unlike coal, natural gas and fossil-fuei powered electricity, is a rapidly renewable resource. Growing trees also absorb CO2 pollution. But burning wood has a higher direct health risk than other fuel sources, although operational and installation costs are low. Weigh all the options, including solar and geothermal, before you decide on your heating system. We'll follow up with information on these other sources, so stay tuned.
SLOW BURN. As you can see, different species of wood produce more or less heat per lb. In the case of tiny houses, this may work to your advantage. By burning lower btu woods, you can run the stove more consistently without overheating your space.
CLEANER BURNING. Wood stoves with catalytic converters produce much less air pollution than older models, which have been linked to asthma and other health conditions.