Since I purchased my first home in 1981, I have heated my homes with wood burning stoves. Some were very efficient, while others were better than the alternative of electric baseboard heat (my first house). With all of them, wood heat has been a comfortable, inexpensive source of winter warmth. I have also learned how the stove and chimneys work properly together by trial and error and research.
Do I need a damper on my wood burning stove? Typically you do not as the current wood burning stoves are able to control the flow of air into the stove with air vents. To further explain, the way a stove works and the types of chimney your stove is connected to is also a factor. I will expand on this in the article.
The Beginning of Air Tight Stoves
Back in the early 1980s, as the “energy crunch” was starting to loosen its grip, we started to look for alternative ways to heat our homes. Turning the thermostat down to “save energy” was getting old. Fireplaces were just not efficient as most of the air feeding the fire; literally just went up the chimney.
The glass doors on fireplaces helped a little but fireplaces still burnt too much wood for the small amount of heat that radiated about 5-7 feet from the hearth. The fireplace had a damper in the chimney, but closing it, even a little would generally send smoke into the house. That never went over well!
Some clever inventors began welding up steel boxes on legs with a door that could be shut to seal the air from entering. The box was lined with firebrick, and a smokestack was added. A sliding or spinning air vent was added, generally to the door and the “Air Tight” stove was born.
Most of those early wood stoves still leaked some air into the firebox. To control the flow of air, a damper was added in the stove pipe to reduce the flow of air and smoke out of the stove. Today’s stove can nearly shut off the flow of air into the firebox, and so, the need for a damper has all but been eliminated.
Reducing the airflow did however create an issue that eventually caught the attention of our government. By reducing the air flow, which made the stove more efficient, the fire did not burn as hot and caused two issues.
- Wood burning stoves, starved for air, began to build up a tar-like substance on the insides and on the chimney known as creosote. Creosote, when introduced to enough heat and direct fire, will burn extremely hot and can easily burn out of control.
- The reduced air flow also caused an increase in PM or Particulate Matter, to be sent up the chimney and out into the atmosphere. Some of the PM is harmful to breath.
Stove Types
In the mid-1980s, the United States EPA became involved, and wood stoves began to change. Manufacturers were required to limit the output of the PM or Particulate Matter of the stove. The rules took effect in 1988. The regulations were tightened in 1998 and then again in 2015. Stricter regulations will be enacted in 2020 and manufacturers are working to reach those standards.
Two types of wood burning stoves are currently manufactured that meet the EPA standards. They are Catalytic and Non-Catalytic. This is a basic description of how they work.
Catalytic
Catalytic stoves have a device inside that works like a catalytic converter on a vehicle. When brought to a required temperature, the catalytic device will re-burn the smoke and burn off the excess PM’s before the smoke exits the stove.
Non-Catalytic
Non-catalytic stoves do not have a catalytic device but instead have a baffle that the smoke must pass over. Heated air, is introduced above the baffle and the PM’s are burnt off in this section of the stove.
Both types of stoves reduce the PM to make them efficient enough to pass the EPA standards.
Fireplace
So you may ask, what about a fireplace or campfire?
A fireplace will burn 35 pounds of hardwood, in about two hours. In my wood burning stove, 35 pounds of hardwood will last eight to ten hours depending on the air flow and heat my entire home to 72 degrees (depending on the outside temperature).
Creosote
As I mentioned earlier, the reduced airflow will cause creosote buildup in the stove and chimney. Several factors will reduce this buildup. The primary factor to reducing creosote buildup in the stove and chimney is the moisture content in the wood that is being burned.
Dry, seasoned hardwood is essential to keep the chimney clean and free of creosote. I would recommend that firewood is cut, split and stacked a minimum of nine months before burning. I prefer my wood to set for a full year before burning. This gives the sun and the wind time to do its job and pull the moisture out of the wood.
The vast majority of fires in homes with wood burners start in the chimney. The cause of the fire is creosote build up that was not properly addressed or cleaned out.
In older stoves, if a chimney fire started the homeowner would close the damper to try and stop the flow of air to the chimney. Stopping the airflow would generally cause additional issues.
The fire would still be burning in the wood burner, and the smoke in the stove would have to go somewhere. So it would “leak” out the chimney pipes below the damper and into the house.
Now, with the efficient control of air flow into the wood burner, the input air can be shut off, the fire is quickly cooled, and the chimney fire will burn out from a lack of oxygen.
This makes the newer wood burning stoves safer and more efficient. So if the stoves are safer, why do we still have fires in the chimneys? Generally, it is caused by burning wood that has too high
Chimneys
The three types of chimneys typically used for a wood burning stove are; masonry, triple wall, and double wall chimney pipe. Each has its advantages and reasons for use.
A masonry chimney looks great on most homes and is by far the most expensive to install. It is usually built while the home is under construction or is a construction project of its own. A
If you are not able to complete this inspection yourself, have a professional do it. Even for the hardcore do-it-yourself homeowner, completing a masonry chimney inspection is one of the most important maintenance items to be completed on a regular basis.
A triple wall chimney is the next most common chimney for wood burning stoves. The outer wall is kept cool by the air pockets between the two inner walls. It works well and can handle most wood stove types.
The premium chimney for a wood burning stove is a double wall chimney. A double wall chimney has high-temperature insulation between the two walls and is typically rated for up to 2300 degrees F. This type of chimney still requires inspection and regular cleaning but is built to handle the high heat of a catalytic stove and the cold from the outside air.
If You Really Want a Damper on Your Stove
So you still want a damper on the chimney of your stove. Here is my recommendation. Dampers can be installed as a stand-alone damper that is added to your existing chimney pipe or as an 8″ long pipe addition with the damper already installed.
When a damper is installed in a wood burning system, it would be in the single wall connecting pipe. This is a pipe that connects the stove outlet, to the double or triple wall chimney that runs from the ceiling to the exterior of the roof or wall. This single wall pipe will typically be from five to nine feet long. The damper would be installed in the middle of this vertical pipe.
Additional Questions
Can I clean my own chimney? If you are capable of safely getting to the top of your chimney pipe and handling the chimney sweeping equipment at this height, then yes. If you are not good with heights and do not know what to look for in your style of chimney, then no, have a professional inspect and clean your chimney.
Can a wood burning stove be modified? Modern wood burning stoves are built as a system. This system requires all the equipment in the stove to work properly. Modifications should only be made by a knowledgeable; professional that understands the physics of a modern wood burning stove.