Are you unsure of how much wood you'll need for the burn season? Wood consumption varies greatly depending on the type of fireplace or stove in use. An ideal baseline is to figure 1 cord per 7 full days of burn for a large open fireplace. Non-catalytic wood stoves will use 1 cord every 30 to 60 days and catalytic wood stoves will use 1 cord per season for high efficiency models. Further into this guide, we will cover how consumption varies, how to build a more efficient fire, and why cord measurement is important to understand.
We'll also cover how to measure the volume of the firewood you are buying, tips for sourcing and storing firewood, and strategies for building efficient, clean-burning fires.
Researching Your Firewood Source
The first step in estimating the amount of wood you'll need is understanding how firewood is measured and sold. The standard unit for measuring firewood is the cord.
What is a Cord of Wood?
A cord is defined as a pile of wood 4 feet tall, 4 feet wide, and 8 feet long. This corresponds to a volume of 128 cubic feet (including the small gaps of space between the pieces of firewood). In order to qualify as a true cord, the firewood must be neatly stacked with minimal gaps between the logs.
- 1 cord = 4 feet tall x 4 feet wide x 8 feet long = 128 cubic feet
Sometimes the logs are stacked with a shallower depth. If the width of the pile is only 2 feet instead of 4 feet, you would need a pile that was 16 feet long and 4 feet high in order to make a cord.
Full Cord, Face Cord, Stove Cord
There is some confusion with the term cord since there are other variants such as "stove cord", "kitchen cord", and "face cord". These terms do not have standard, agreed-upon meanings.
For example, a "face cord" is sometimes used to mean 1/3 of a full cord, but it can also refer to a full cord that is made up of 16 inch logs.
When you are comparing prices and buying firewood, make sure that you know exactly what the dealer means when they say "cord". Not only should you clarify the quantity of wood that you are buying, but you should also make sure that the width of the logs will fit in your fireplace or stove—unless you are willing to go to the extra work of cutting it.
Avoid vague descriptions such as "truck load" or "pile" unless you are able to accurately compare what you are getting to the standard cord. Otherwise you may end up over-paying for firewood.
How Much Heat is Produced by a Cord?
One of the main advantages to buying wood by the cord is being able to calculate the amount of heat the wood will produce when it burns. The heat produced is measured in MMBtu, which is the same unit used for selling quantities of natural gas.
(Btu stands for British thermal unit and represents the amount of heat required to raise one pound of water one degree Fahrenheit. One MMBtu = one million Btu.) Different varieties of wood produce different amounts of heat, but you can refer to this chart to compare the MMBtu per cord for different varieties of wood.
Average Cost of a Cord
The average cost for a cord of wood varies depending on the species and quality of the wood, the time of year, and where you live.
In the southern U.S., a cord of hardwood might cost $150 to $200 in the spring and summer and $250 to $300 in the winter. Prices in northern states could range from $300 to $400, depending on supply and the season.
Spring and summer are typically the best time to source firewood, since the lack of demand often lowers prices. You can also try doing a Google search to find arborists or tree-trimmers in your area that sell firewood on the side. These vendors often have lower prices since the wood is a by-product of their services.
Hardwoods are more expensive than softwoods because they make better fires. Storage and seasoning also affects firewood quality and price. Fresh cut wood has a very high moisture content, so it is difficult to burn and creates lots of smoke. Seasoned wood is wood that has been cut and left to dry until it reaches a more ideal moisture content (around 20%). If you are seasoning wood yourself, you should expect softwoods to take around 6 months and hardwoods to take a year to dry.
Buying and Storing Firewood
Wood varieties with mid to high density (hardwoods) are more desirable because they burn slower and create less smoke. Some examples of hardwood include:
Conifers (softwoods) like pine, fir, spruce, larch, and hemlock are not recommended because they burn fast and hot. The higher burn temperature could damage some wood-burning stoves, and the faster rate makes them less cost effective. They also produce more smoke and contribute to the buildup of ash and soot in chimneys due to the high volume of sapwood they contain.
If possible, inspect the wood in person before making a purchase. This way you can ensure the quality of the wood that you are buying, as well as whether the wood is stacked neatly and sold by the cord.
When storing firewood, it is best to keep the pile 20 feet from the nearest door in order to keep pests and any small rodents from having a direct path from the woodpile to your inside your warm house. Don't stack the wood directly on the ground; instead, you can use a firewood rack or wooden pallets to keep it off the ground. This will allow for airflow and will also cut down on the insects. Never spray your wood with pesticides since you don't want to burn the pesticide chemicals inside your house.
When stacking wood, allow for airflow on all sides. You can use a tarp on the top to protect from rain, but leave the sides of the pile at least partially exposed to allow for airflow. It is also a good idea to have an organizational system so that you use the older, dryer wood first.
If you want to store some wood inside next to your stove for easy access, you'll want to avoid storing it within 3 feet of your stove to avoid an increased fire hazard.
Open Wood Burning Fireplaces and Fire Pits
Traditional masonry fireplaces and other open fireplaces are the least efficient wood-burning appliances due to the fact that they offer very little control over the fire's oxygen supply. The average 36 inch open fireplace can burn four 16 inch logs per hour and consume an entire cord of wood in just one week. Open fire pits have no air restriction and will consume firewood at a similar rate.
Arranging Logs for a More Efficient Fire
The configuration of logs also affects how quickly the wood will burn. Crisscrossing the wood "log cabin" style is less efficient and will make the logs burn faster because it creates a chimney effect. One way to achieve a longer burn time is to build a top-down fire like the one below:
How to Build a top-down fire
- Start with a layer of the largest logs
- Place a layer of medium-sized logs directly on top and perpendicular to the larger logs
- The next layer should be small (1 inch diameter) pieces laid perpendicular to the medium logs
- Place kindling on the very top and wedge newspaper in the kindling.
- Light the newspaper
Since the burn will progress downward, away from the flow of oxygen, the top-down burn arrangement can extend the burn time of the fire significantly. A properly built top down fire can double burn time over a log cabin style fire, effectively halving your fuel consumption. Standing the logs with their ends all pointing toward the middle (teepee style) creates a similar effect that will result in a slower burn time.
Modifying an Open Fireplace
If you already own an open fireplace and are interested in making it more heat efficient, there are some modifications you can add in order to gain more control over the fire's oxygen supply. This includes adding glass doors with a built-in vent control.
Don't attempt any modifications unless approved by a professional. Altering the airflow of your fireplace must be done properly to ensure appropriate ventilation and safety.
Closed Combustion Fireplaces and Stoves
Closed combustion appliances are far more efficient than open fireplaces because they allow for strict air control. Most models feature a sealed chamber where the fire burns behind glass doors and adjustable air vents to regulate the oxygen supply. Since the air intake is limited to only the amount needed to keep the fire going, the burn is more efficient and there is far less heat lost up the chimney.
Non-catalytic appliances typically burn cleaner and more heat-efficiently at moderately high temperatures (higher air settings). The average non-catalytic closed combustion appliance can last 3 to 4 hours on three 14 inch logs at a high air setting. Decreasing the air supply to a low or "overnight" burn setting can achieve 6 to 8 hours, depending on the model.
Depending on how often you use the high or low burn settings, a non-catalytic model can go 30 to 60 days on 1 cord of wood.
Catalytic stoves are even more heat efficient than non-catalytic appliances. Smoke and other byproducts of combustion are passed through a metal-plated grate that causes the smoke to ignite. This increases the amount of heat available and cuts down on the amount of smoke and creosote.
Although they are more heat efficient, these models work best at lower temperatures and are suited for situations where a long-lasting, low temperature fire is preferred over the higher temperature fires of most non-catalytic stoves.
At low temperatures, an average catalytic stoves can reach 30 hours of burn time without having to add more wood. On higher settings, the burn time is approximately 8 to 12 hours. With such high efficiency in the catalytic stove models, it is possible for a cord of wood to last an entire season.
One downside of catalytic stoves is that they require some maintenance of the catalyst. If using the proper fuel (i.e. not burning treated lumber, glossy paper, or other things that might clog up the catalyst), the catalyst should last around 5 years. Catalytic stoves also require you to preheat the catalyst to a certain temperature before closing the damper.
The average consumption for different fireplace models can give you a guideline for estimating what you should expect to use during one season, but it is important to remember that burn time and wood consumption can vary from stove to stove. Even appliances from the same category may have different efficiency ratings.
Since wood is usually more expensive in the winter, it is a good idea to purchase a little more than you think you will need to make sure that you will have plenty. If stored properly, you can use any leftover wood the following season.
If you are experiencing unanticipated wood consumption or have questions about new appliances, our techs are available to assist you and would be glad to help you troubleshoot any issues you might have.