Owning and using a wood burning stove for the past 40 years has provided me with a history in the field of burning wood. Throughout this time, I have burned wood as the primary heat source for two different homes. This article outlines my personal experience and research I have done on the subject of the source of fires in homes.
Do wood stoves cause fires in homes? Wood burning stoves are NOT a primary source or cause of fires in homes. The most common cause of home fires (over 58%) is cooking incidents typically started around the range or stove. The second most common cause is heating appliances, but the vast majority of those incidents (32%) revolves around portable heating devices like electric heaters.
When wood stoves do play a part in a home fire, the vast majority of those incidents relate to a chimney that was improperly cleaned or not cleaned at all. The woodstove itself is rarely the primary cause of a home fire.
Wood Stoves
Many people are leary of even lighting a fire in a home when, in fact, most homes have fires burning inside on a regular basis. The natural gas furnace or hot water heater has an intense flame burning to heat the air or the water in a home. The difference is those fires are contained and out of sight. You also do not have to light them (unless you still have a pilot).
Lighting a fire in a wood burning stove may seem intimidating to some but is a safe and natural method for heating a home. When a woodstove “system” is properly installed and maintained, it is as safe as any other appliance in your home. I have outlined some tips that will make any home with a wood stove safer, listing common housekeeping and maintenance items that should be followed for any wood stove.
Stove Types
When purchasing a wood burning system, choose a system that will fit your home in type and size. A wood burning system needs to be purchased and installed as a complete system. The stove must fit the home, and the chimney must be the type and rating to properly vent the gases exhausted by the stove. All the pieces and parts must match and fit properly.
Here is a list of stove types: Catalytic and Non-Catalytic Wood Burning Stove, Pellet Burner, Fireplace Insert, Free Standing Stove, Hydronic Heater (Outdoor Boiler), Here is a brief explanation of each.
Wood Burning Stove
Basic wood burning stoves have been around since the early 1980s. They have evolved (I don’t believe in evolution but in the case of a steel stove that burns wood, OK) from a simple box with a chimney to the high tech models produced today. The big changes came with the regulations imposed by the EPA in 1988 that requires the manufacturer to sell only products that meet or exceed the output of PM (Particulate Matter) implemented by the EPA.
In order to meet those standards, several methods have been employed by the manufacturers.
The first method uses a catalytic converter (similar to a vehicle) to re-burn the emissions before they leave the stove. In the re-burn process, the PMs are reduced, and the smoke that leaves the stove is cleaner than the original stoves.
The other version is called a non-catalytic stove (very inventive). After the smoke leaves the main firebox, it passes over a plate in the stove where pre-heated air is introduced, and the PMs are again burnt up in a re-burn process.
Stoves that do not have one or both (combination) of these emission-reducing systems were either built in the early 1980s or have been homebuilt. Those stoves will produce a product formed in the smoke called creosote. All wood stoves will create some creosote, but due to the lower operating temperature and lack of emissions eliminating system, these stoves’ will naturally create more.
The danger of creosote occurs when it builds upon the inside of the stove walls and chimney lining. The tar-like substance is capable of igniting and burning at a very high temperature. A chimney fire, if contained is not dangerous in itself. Most chimney systems are designed to withstand the temperature and intensity of a 5-15 minute chimney fire.
A chimney fire becomes a hazard if:
1. The owner of the stove does not shut off all air sources to the stove. Removing the air to feed the fire will extinguish the fire quickly.
2. If the chimney does not have an adequate chimney cap to catch all hot debris that may exit the chimney. Hot and burning ashes may exit the top of the chimney, landing on the roof or in an ignitable surface such as wood chips or leaves. A good chimney cap with a heavy screen will help avoid this issue or at least break up the ashes into small pieces that burn out before landing.
3. The chimney lining has deteriorated, and the fire leaves the chimney into the chase or attic. A trained inspector will determine the condition of the chimney and should have the homeowner repair any defects that could cause such issues.
Chimney Cleaning
Cleaning the chimney, either by a professional or done by yourself, will reduce the possibility of a chimney fire exponentially. My recommendation is to clean the chimney every month in the winter and have it inspected at least one time a season. This ensures a clean, safe chimney system.
As mentioned earlier, creosote will build up in the chimney when the wood burner temperature is reduced. This generally happens in the fall and the spring when the temperature is warmer, and the heat required from the stove is reduced. This is when you have to pay more attention to the chimney and clean it more often.
Free Standing Stoves
Back to stove types. A free-standing stove is a wood burner (or pellet stove) that sets in a room with its own chimney system. The advantage of this system is the stove heats the room by radiating the heat from its surface. This system is efficient as only the heat up the chimney is wasted. The remaining heat is sent into the home to heat the space intended.
Fireplace Insert
A fireplace insert is placed into an existing fireplace (the least efficient heat source you can burn), closing off the opening and operating like a normal wood burning stove or pellet burner. The drawback is that you are only getting heat from one side of the stove. Most inserts have a blower system to send the heat out and away from the stove to heat addition square feet of the home.
Generally, the fireplace area is brick, and this large area of stone, brick, and mortar makes an excellent thermal mass. A thermal mass holds heat for many hours after the fire burns out and will continue to heat the home (on a long winter night).
Pellet Stoves
Pellet stoves are a fast-growing type of the wood burning industry. They are available in free-standing versions or as an insert for an existing fireplace. Pellet stoves are the cleanest burning stove generally due to the controlled nature of the fuel. The pellets are manufactured to have a very low moisture content. Reducing the moisture content also helps reduce the creosote buildup in the stove and chimney.
Reducing the moisture also reduces the emission output of the stove. Pellet stoves are typically able to meet the highest emission standards that will be introduced in 2020.
Since these stoves are controlled electronically, they can add fuel (pellets) and air (controlled by a fan), as necessary to produce the desired output temperature and a very precise rate. This makes the burn process more efficient and safe. The chance of a chimney fire is almost zero as the emissions are reduced unless inferior pellets (or other fuel like corn) are used.
The chimney system used for pellet stoves is similar to the chimneys used for an 80% efficient natural gas furnace. The output temperatures (250 – 300 degrees F) are also similar. A typical wood stove system will exhaust heat between 350 – 400 degrees F. The chimney system for a wood burning stove is recommended to withstand 1750 – 2300 degrees F.
Hydronic Heater
A typical hydronic heater is located outside a home. There are pros and cons to this arrangement. The pro is the wood does not need to be brought into the home. This makes less work as the last step in the process, moving and stacking wood, is eliminated. This also eliminates the dirt and bugs that may come in with the wood, Any bugs that hibernate tend to wake up when they hit 70+ degrees F for a few hours. The last positive note is there is no chimney to run through the roof or attic. This saves on installation, cleaning, and the possibility of a chimney fire near the house.
The negative aspect of the wood stove outside the house (and maybe 100 feet away) is you will have to go outside, up to three times a day to load the fire. They also require as much as three times as much wood as a standard wood stove. This is due to the lack of radiated heat and the loss in transfer of the heat from the firebox to water and sometimes back from water to heat exchanger.
Choosing the Correct Stove
Choosing the correct stove size and type is a critical factor in the safety of your home. You must choose a stove that fits the space and type that properly heats for the area. Lets’ look at the size of the stove first.
Stove Size
For a stove to burn efficiently and safely, it should be chosen carefully to warm the area. It was designed to heat. Just like gas furnaces, wood stoves are rated in BTU output. Stoves BTU’s are typically given as a range. Once you know the BTU’s required to heat an area (part or all of a house), choose a stove that meets that requirement in the upper ¾ of the range for that stove. This will provide some contingency heat for the really cold days (usually 1-2 weeks out of the winter).
Use this site to calculate BTU based on your home size and your location.
If you choose a stove that is too small, the stove will have to operate at a higher than designed temperature. This could cause stress fractures in the stove or chimney system. Burning at higher than designed temperatures can also damage the doors, glass, seals, or electronic systems of the stove or cause them to fail earlier than necessary.
Burning a stove that is too large for an area is also detrimental. If the stove is too large, and you are burning it at a lower temperature constantly, the emissions system can be damaged or fail prematurely. The recommended temperature of a stove is optimum to keep these systems operating clean and safe. Burning too low will typically clog the catalytic converter or cause it to fail early. For the converter to operate properly a minimum temperature must be reached and maintained for the emissions to be re-burned.
Also, creosote builds up when stoves are burnt at a lower temperature than recommended. The lower temperature of the fire does not consume the moisture that the wood has left, and it collects on the stove and chimney walls. Creosote that builds up can be ignited by a hot fire, and the stove and chimney will burn fast and furious.
Best Practices for a Safe Wood Burning
Pellet Stoves
For pellet stoves, the most important factor would be to purchase and burn a good quality pellet. The best pellets will have a consistently low moisture content, low amount of bark, and no dust in the bag when dumped out. Some moisture in the wood is required for it to burn correctly, but a 10-13% moisture content in pellets is ideal. This will allow the pellets to burn efficiently and clean. A hardwood mixture pellet with very little bark will burn hot and leave very little ash to be cleaned after the burn. It will also not leave any residue from emissions in the chimney which could be an issue.
Wood Stoves
You also need wood that is low in moisture content for your wood stove. 12-15% moisture is a good range to aim for. It is up to you to make sure that your firewood is dry. Wood must be cut, split, and stacked to dry for 6 to 12 months to dry depending on the type of wood and the climate where you are located. Dry air speeds up the process, and moist air slows the process.
Any type of stove requires properly seasoned wood to burn properly. Moisture in the wood carries the emissions in steam to the walls of the stove and chimney where it builds up and could become dangerous if not cleaned. Additional moisture in the wood also requires a hotter fire, which is cooled by the moisture as it is released from the wood. This wastes valuable BTU’s on reducing moisture and not heating the home.
Hydronic Heaters
Hydronic heaters are not an exception, other than the safety issue of the chimney is a non-issue when the stove is 20 or more feet from the house. A chimney fire is not an issue at this distance, and most hydronic heater chimneys are only 10 feet or less tall. I would still recommend well-seasoned wood as it is more efficient, and the boiler typically requires a hotter fire than an indoor wood stove.
Monitoring Your Stove
Regardless of the type of stove you have, knowing the temperature at all times is critical. If your stove burns 24/7 like many wood burners that use wood as the primary heat source, knowing the temperature of your stove is essential information.
Many factors can change throughout the day. The wind can pick up, or a vent can be left open slightly too much accidentally. Knowing the temperature will give you peace of mind when operating a wood stove while you are not at home. The TempSure wood stove digital monitoring system will give you that peace of mind. The digital monitor will connect to your home WiFi system. A free app on your smartphone will provide you with the temperature of your stove anywhere you have a wifi signal.
Pre-set high and low limits can be input, so you will receive an alarm anytime the stove temperature exceeds these limits. It is simple to use and easy to connect with a magnetic sensor that attaches to stove at any point you determine to be the hot spot.
This is a brand new product devised just for wood stove owners. Check out TempSure.net to order one today.
Conclusion
Burning wood is an efficient and safe alternative home heating source. Whether you burn wood as a backup to your furnace or burn wood as your primary heat source, it is a safe source of heat in any home. Just following a few simple steps to keep your stove and chimney clean.
Use dry, seasoned wood from fall to spring to keep a warm, consistent heat that will minimize creosote buildup.
Inspect the chimney regularly and clean the creosote and other buildups out as needed.
Monitor your stove with the only system available to view the temperature from anywhere, anytime with real-time alerts for high and low temperatures. Tempsure.net