Heating a home with a wood burning stove for the past 40 years, I have experienced and learned many lessons about wood heat. The most important lesson has been to keep my chimney clean and free from creosote and other harmful buildups in my chimney.
How do I reduce creosote buildup in my chimney? The primary means of reducing creosote buildup in a chimney is by burning dry, cured wood.
There are several other systems and procedures when burning wood that contribute, or should I say do not contribute to creosote buildup that I will also expand on in the article.
Burning Dry Wood
Dry firewood is the key to a proper burning fire, in a wood burning stove for heat, or just on an outdoor campfire. Some of the moisture in the wood will be eliminated, either by drying over time or by the heat from the fire.
The ideal moisture content for wood is around 20%. This allows for some moisture in the wood to control the burn. Wood should be cut and split at least six to nine months before it is burned to allow time for drying.
I prefer to cut my wood a year in advance. I then stack the wood on pallets (off the ground) and allow it to air dry. Air drying the wood in the sun and wind will give the best results and get the moisture content down to the ideal of 15-20% range.
Burning Wood that is too Wet
When burning wood that is to wet (moisture content of 30-40%), the higher moisture in the wood must be accounted for. It has to go somewhere! You have no doubt heard wood placed on a campfire and heard it sizzling. That is the excess moisture content being burned off as steam.
When that happens in a wood burning stove, it causes several bad things to happen:
- Heat is wasted by “burning” the excess moisture out of the wood.
- The heating temperature of the stove is hard to maintain.
- The moisture and other gasses that should be burnt up in the wood burner collect in the chimney flue pipe.
Wasted Heat
When burning firewood that is too wet, the first one or two hours of the burn may be just drying the wood to an acceptable moisture level. The heat is consumed on drying the wood and not on heating the home.
Heating Temperature
Fire requires three elements to burn: fuel, oxygen (air), and heat. When the heat is removed, the fire goes out. When the heat is reduced, by adding moisture to the wood, the fire has to have more heat. For the fire to have more heat, it must either have more fuel (wood) or oxygen.
Typically there is only so much room in a wood burning stove for wood (I like to stuff mine as full as I can get it), so adding fuel is not an option. Increasing oxygen (air) to the fire is the best way to get it burning faster and hotter.
Unfortunately, this creates several problems (or opportunities for you salesman readers).
- The air must come from somewhere, and typically it comes from the home. Opening the vents that feed the fire draws more air from the home and will cool the home down like an open fireplace that makes every room in the house cold except the room with the fireplace.
- If the wood stove is not watched closely, with the vents left open, the fire could quickly burn out of control. A new temperature monitor I recommend will help alleviate this worry.
Moisture Up the Chimney
When wood burns, the reaction sends particles
When too much moisture is in the wood, the temperature of the resulting chemicals going up the chimney is reduced. This allows the moisture as steam carrying multiple chemicals to collect and attach to the wall of the chimney.
This buildup is called creosote. When it dries, it is a tar-like substance that becomes highly flammable. If flames reach the creosote at the bottom of the chimney (from the firebox), the entire chimney can burn. This uncontrolled burn is called, believe it or not, a “Chimney Fire.”
Chimney Fires
Chimney fires are not something to joke about and result in the majority of fires in homes caused by wood burning stoves. Chemicals are available that can quickly be thrown into a wood stove to extinguish the chimney fire (by removing the oxygen).
Typically a chimney fire can be quickly stopped or slowed in a wood burning stove by shutting down the air input to the stove. Some air will still feed the fire from the top of the chimney down. This is where you have to be aware of your own stove, and the
Allowing Adequate Air Flow
One appeal of a wood burning stove over a fireplace is the ability to reduce air flow to the fire. This gives the owner the power to control the fire. Controlling the airflow is the primary means of regulating the temperature of the stove and the heat it produces for your home.
Reducing the air flow to the wood stove also reduces the amount of warm air we are pulling out of the home to feed the fire. You may have noticed in a home with a fireplace, areas of the home away from the fireplace are generally cool. This is because air to feed the fire is being drawn up the large chimney and out of the house.
This is not very efficient! It wastes wood and heat, although it is great to watch the fire burn! Just not a great way to heat a home.
The key to an efficient wood burning stove, is to burn the fire at a temperature that allows a good, continuous draft up the chimney, without wasting wood. A typical wood burning stove burns at 250 – 425 degrees F. Each brand, model, and size of stove will burn differently and will depend on the home or size of the rooms that require heating.
You will need to know your own stove, but you should monitor the temperature of the stove constantly when it is burning. A new product is available that allows constant monitoring of your wood burning stove.
With this device, a stove’s temperature can be monitored from your smartphone. This is a leap ahead in technology and protection for you and your home.
Proper Chimney Temperature
As mentioned, the
Several factors that affect the temperature of a chimney are:
- The height of the chimney. The taller the chimney, the greater the draft. If the chimney is too tall, the long inside surface will be difficult to clean. Ideally, the chimney is three feet above the tallest point on the roof. This is outlined in NFPA 211 which includes many guidelines to wood burner and chimney safety.
- The area (square in masonry or round in steel) of the chimney. A chimney that is too small in diameter for a stove will restrict the flow of the smoke. A chimney that is too large will not draw the warm air up as it should and also causes particle build up.
- The type of chimney. Masonry, triple wall, or double wall chimney. Each has it’s own positive and negative qualities, but typically a double wall chimney is the best type for a wood burning stove. Masonry generally looks the best as it has a permanent aspect to it.
- If the chimney is not masonry, the type of material insulating the outside of the chimney pipe is important. This makes a difference, primarily if the pipe is on the exterior of the home. If the pipe is too cold, the chimney will not draft properly and cause the smoke and particles to collect on the inside.
Additional Questions
On the topic of creosote buildup and chimneys, a few other questions are relevant. One is, do I need a damper on my chimney with a new wood burning stove? Typically, the new
If it is important to burn dry wood, what is the best type of wood to burn? That depends on what type of wood is available where you live. The best wood to burn in my area (the mid-west in the United States) of the country is oak. I will write more on this in additional articles soon.