What features does one expect to find embodied in a small wood burning stove used to heat a tiny home? The obvious ones are an efficient use of small amounts of fuel for a maximum heat output, a small footprint with a well-insulated stove pipe, and small clearances to combustible walls and furniture nearby. Less expected features include an efficient way to remove burned fuel ash, a lighter overall weight, and a reduction in air polluting emissions in the stove’s smoke. These are all features of the Kimberly™ gasifier wood burning stove shown below, which is used as an example of a small stove that is suitable for a tiny home. (See our blog on gasification to learn more about this process. Link)
Specifications for the Kimberly™ gasifier wood-burning stove.
- Height is 25.5 inches.
- Diameter is about 10 inches.
- Weight is 56 pounds.
- Flue is 3 inches in diameter with a double wall.
- Holds two logs 3 inches in diameter x 10 inches long.
- Heats up to 1,500 square feet of well-insulated space.
- Has a cook top for heating water or a can of soup.
- Approved for just 6 inches of clearance on sides and back of flue.
- Exhaust gasification, with an emission of only 3.2 grams/hour.
- Certified by both the EPA and the CSA.
Having used larger wood burning stoves and fireplaces for the last half century, I have a few observations and suggestions that may help you and other readers better understand some of the peculiarities of wood burning stoves. The recommendations that follow apply especially to smaller stoves such as the Kimberly™.
Although each stove seems to have a “personality” of its own, they all need fully dried wood in order to burn well and efficiently. In general, the wood should be cut, split, and allowed to dry for at least one year before using. This is especially true for smaller wood stoves that have small fireboxes. All types of wood, but especially softwoods such as pine and fir, will cause the deposition of creosote on the cooler surfaces both inside the firebox and in the chimney system, if they are burned before being fully dried.
During the initial phase of starting a fire, there will be less buildup of creosote on the stove’s interior walls and glass door panel if the firebox is preheated by burning a small amount of paper or cardboard. Let that fire die back, and then proceed to build and start the main fire.
Let that second fire heat the firebox to around 250o F. This simple trick will do two things that improve the performance of any wood-burning stove, large or small. First, it results in less smoke and creosote forming during the creation of the fire, and secondly, it produces a fire that is hot enough to burn off the small amount of creosote deposited during the fire’s startup phase. (Please note that a temperature of 250o F in the firebox may be too hot for your tiny home except during the coldest days of the year. If this is a problem you face, then bring it up to this temperature briefly to get rid of the creosote buildup, and then cool it back down before the heat buildup in the home itself drives you out. Alternatively, open all the windows and turn on all of the fans.)
For a gasifier stove, this action rapidly gets the interior heat inside the stove high enough for the gasification process to begin. It also will keep the chimney system cleaner and reduces the frequency of your absolute need keep the chimney free of creosote. If you forget to clean the chimney pipes at least once a year, you are guaranteeing that there will be a chimney fire that may burn down your tiny home!
A final note that applies to all wood-burning stoves whose airflow can be controlled. In order to extend the burn time so that you can get a good night’s sleep or leave your tiny home to cut more wood for those winter fires, you must close the air input vents. This will convert your wood stove from an efficient burning machine to one the produces charcoal. Because this also significantly reduces heat production, this action will shut down the gasification process and increase the deposition of creosote. This is unfortunate, but essential if you don’t like to restoke the fire every hour or so during one of those long winter nights.
Kendall W. Corbin
October 23, 2017