Firewood has been an effective way to warm a home since the beginning of time. Wood is a renewable resource, but it makes sense to take a few simple steps to use it efficiently. Practicing simple conservation techniques will increase your time enjoying the beauty of a warm fire and reduce the amount of time spent splitting and stacking the wood.
Why should I use consider using wood to heat my home?
Heating a home with wood can be enjoyable, efficient, safe, simple, and environmentally responsible. Correctly done, wood can keep you and your family warm during a winter power outage and even allow you to cook your food for an extended period. Heating with wood changes a dreary winter into a cozy, enjoyable time of year.
My Top 3 Tips for Efficiently Heating a Home with Wood
- Start with the right woodburning appliance—efficiency varies greatly by appliance.
- Correctly design the chimney—makes all the difference in your ability to enjoy the fire.
- Properly seasoned firewood—improves efficiency and reduces buildup of creosote.
In this post, I will share with you some of the helpful lessons that I have learned from years of working as a mason and helping customers design efficient wood burning appliances.
#1—Choosing the Proper Wood Burning Appliance
There are only a few options when it comes to heating your home with wood. You can use an outdoor wood boiler, a wood stove or pellet stove, or a masonry heater. Wood burning fireplaces are also possible if they are centrally located in a home. Some of these wood burning appliances are much more efficient than others.
Calculating Firewood Requirements
How much firewood will you need to keep your family warm through the winter? This will vary considerably based upon your climate, area being heated, level of insulation, and airtightness of the home.
For illustration purposes, let us consider an average home in the upper Midwest of approximately 2000 square feet where there are relatively longer and colder winters for each of these woodburning appliances.
Wood Consumption in a Pellet Stove
A pellet stove has a specific fuel requirement. The wood pellets must be purchased. The average cost to operate is between $1750 and $2250 each year. Pellet stoves will burn between 7 and 9 tons of pellets annually. Pellet stoves can certainly meet the enjoyable, efficient, and easy to do aspects of successful wood heating. However, pellet stoves have limitations that should be considered.
Considered environmentally responsible, pellets still take a lot of manufacturing to get into the form of a pellet, not to mention all those plastic bags. Pellet stoves must constantly burn hot to keep the home warm and could be a source of burns.
Pellet stoves require electricity to operate and would not be beneficial for keeping your home warm during a power outage without backup power. Pellet stoves are also not a backup source for cooking your food.
Wood Consumption in a Woodstove
A woodstove is like a pellet stove in operation and function. Cord wood can be acquired for free if you have a supply of trees. Anticipated wood consumption for a woodstove is between 6 and 8 cords of wood per year. Harvesting that much wood requires a lot of work, but it is cheaper than pellets.
A wood stove is dangerously hot during operation. If you purchase the right woodburning stove, you may be able to heat water or cook on the top surface. Not all wood stoves are effective for cooking food.
A woodstove is a great asset during a power outage to help keep you warm. Efficiencies vary considerably from model to model. Also, a wood burning stove has no ability to store any heat and much of the heat from the fire goes right up the chimney. The results in the need for constant stoking to maintain its heating ability, and the reason why so much wood will be necessary for your heating season.
Wood Consumption in Outdoor Wood Boilers
An outdoor wood boiler comes in at the top of the list for wood consumption at 8 to 10 cords on average, with much more not being uncommon. That is a tremendous amount of work and storage due to inefficient use of the wood.
Outdoor wood boilers have become popular for those interested in heating with wood. They can heat your home along with your water. The benefit is that you do not have to see a fire or have a fireplace in the house. A drawback is that you cannot enjoy the cozy environment that a nice fire brings into your home.
Outdoor wood boilers come in at the top of the pollution scale being known for their constant smoking chimney pipes and will need to be continuously stoked around the clock. They can hold substantially more wood than a woodstove however, and do not need to be reloaded as often. Outdoor wood boilers require electricity to operate and so, like pellet stoves, they cannot be used in a power outage event without backup power. You cannot use them to cook your food.
Wood Consumption in a Masonry Heater
Masonry heaters are the winners when it comes to efficient use of wood. You can heat your entire home and cook your meals with only 3 to 4 cords of wood per year. You can also add a water coil with a run to your water heater for domestic hot water usage.
Masonry heaters are a unique heating fireplace. They are both beautiful and functional. They burn hot by design and are therefore extremely efficient in the way they are used as well. Instead of sending the heat up the chimney, a maze of flue channels within the fireplace capture and store the heat for slow heat release over 12-24 hours.
Masonry heaters do not require electricity and are often built with a wood fired bake oven just above the firebox. Masonry heaters have been around for hundreds of years through Europe and our becoming increasing popular in America.
Here is what Mark Twain wrote about masonry heaters when he traveled to Germany:“All day long and until past midnight all parts of the room will be delightfully warm and comfortable, and there will be no headaches and no sense of closeness or oppression. In an American room, whether heated by steam, hot water, or open fires, the neighborhood of the register or the fireplace is warmest – the heat is not equally diffused throughout the room; but in a German room one is comfortable in one part of it as in another. Nothing is gained or lost by being near the stove. Its surface is not hot; you can put your hand on it anywhere and not get burnt…
…Consider these things. One firing is enough for the day; the cost is next to nothing; the heat produced is the same all day, instead of too hot and too cold by turns; one may absorb himself in his business in peace; he does not need to feel any anxieties of solicitudes about the fire; his whole day is a realized dream of bodily comfort…
…America could adopt this stove, but does America do it? The American wood stove, of whatsoever breed, it is a terror. There can be no tranquility of mind where it is. It requires more attention than a baby. It has to be fed every little while, it has to be watched all the time; and for all reward you are roasted half your time and frozen the other half. It warms no part of the room but its own part; it breeds headaches and suffocation, and makes one’s skin feel dry and feverish; and when your wood bill comes in you think you have been supporting a volcano…”
Masonry heaters are a unique, one-of-a-kind heating fireplace. The incredibly efficient design uses only 3 to 4 cords of wood per year. A masonry heater is an investment that will last a lifetime and pay for itself over the years in fuel efficiency. It also adds incredible beauty to a home.
Affordable do-it-yourself kits are available for those who would like to build one themselves at Temp-Cast Masonry Heaters. This is a great way to obtain a one of kind heirloom fireplace that will truly make winter something you look forward to, and not dread.
#2—Correctly Designed Chimney System
A proper chimney system is critical to enjoying your wood burning appliance. The last thing you want is to have smoke and poisonous gasses lingering in your home. Not only is this dangerous, but it prevents you from being able to comfortably enjoy your fire.
Place Chimney Inside Building Envelope
The first step in designing a good chimney system is to install the chimney inside the building envelope of the house. This means that a chimney should be within the heated area of the home as long as possible. In a best-case scenario, it will penetrate the home at the highest point of the heated area.
Establishing Good Draft
In order for the chimney to establish draft, several things need to happen. Let us quickly review these.
Air Temperature Effects on Draft
One of them is that the air inside the chimney itself is warmer than the outside air temperature. Imagine a hot air balloon. What happens if the air inside the balloon is cool? The balloon sinks, but when it is hot, the balloon floats and rises. Your chimney is much like this because it is a contained column of air, and if this air is cold, it will be easier for it to sink than to rise.
For this reason, using a chimney on the outside of your home does not work well. If the air in the chimney is the same temperature as the outside air on a winter day, then it is colder than the air in the house. This will make it so that your chimney will much more easily send cold air down, than to send it up.
Minimum Chimney Height
Going back to our hot air balloon example. It is not just any balloon that can carry humans through the air. It takes an enormous balloon because the volume of air matters. Likewise, not any chimney height is acceptable. A 10 to 12-foot chimney will rarely draft well because the volume of heated air is not sufficient for proper draft. A minimum chimney height for proper draft is 15 feet and is key to enjoying your fire.
House Air Pressure Effects
Another, and less understood, reality going on that affects draft is where the fireplace should be placed in the house. Considering the chimney as a column of air is understandable, but the house itself is often overlooked as also being a column of air, it is just a wider one! Because of this there is slight pressure within the house itself. The pressure is higher, or positive, near the top of the house, and slightly negative near the basement floor.
This can be seen easier if you imagine a two-story home with a basement. If you open a window upstairs and you open a window in the basement, how does the air flow in and out? Not considering any wind in this situation the air will flow out of the window upstairs and into the window downstairs. This air flow will be more profound as the temperature in the house is greater compared with the outside air temperature.
A way to understand how this affects your wood burning appliance is to understand that the positive pressure that is in the upstairs of a home “pushes” on your appliance. If you open the fireplace door the warm upstairs air will push its way up and through the chimney. Downstairs, this negative pressure “pulls” on your fireplace. If the door is open it will naturally tend to pull air down the chimney instead of sending it up.
This pressure that is created in a home by the temperature difference from inside of the home to the outside is called stack effect. The greater the temperature difference, the greater the stack effect. The greater the stack effect the more influence it will have on your wood burning appliance. If your appliance is upstairs, which is not very practical, it will aid the removal of smoke. If it is downstairs, it will make draft more difficult. So, what do we do, because minimally we want our fireplace on the main level of the home?
The middle of the home is generally where the neutral pressure plane is. This is the area that the stack effect of the home will have no influence upon the draft because the pressure is neither positive nor negative, it is neutral. This is the best area of the home to put a wood burning appliance because there is nothing inhibiting draft. The downstairs is naturally the hardest place to establish good draft with a wood burning appliance.
This is also why it is important to keep your chimney in the heated envelope of the house as long as possible. It keeps the column of air in the chimney warmer than the outside air temperature, and draft will naturally be strong. If the chimney is on the outside of the house and the fireplace is downstairs the column of air in the chimney will be cold and the stack effect will tend to pull the air down the chimney, this is the worst-case scenario. This combination of a downstairs fireplace and an exterior chimney is going to always be a struggle to enjoy.
A main level wood burning appliance with a chimney within the heated envelope of the home will almost always be a joy. The strong draft and neutral stack effect making the chimney system work the way you want it to. A downstairs fireplace with a chimney within the heated envelope of the house is also something that will work. This is provided that the chimney penetrates the highest point of the heated envelope of the home. The reason is because the air in the chimney will be warm and the draft pressure will be greater than the stack effect in the home.
Correct Chimney Design Means Enjoyable Fires
The best way to ensure that you will have a proper chimney system is during the planning stage. Once you have built your system, there is very little that can be done to remediate a poorly designed chimney system. Knowing the basics of draft and stack effect will ensure that you build yourself a proper chimney system. This will give you the ability to enjoy your fireplace every time you light it!
#3—Properly Seasoned Wood is Critical for Success
The final tip is to make sure that you only burn properly seasoned firewood. This is the most important aspect of burning wood once you have picked your wood burning appliance.
Why is Properly Seasoned Wood Important to Efficient Heating?
The first reason is that high moisture content wood cannot achieve a high enough temperature to burn efficiently. Excess water in the wood means that the fire must “boil off” the excess water before it can burn the wood. Water does not burn! In fact, neither does wood! Heat turns the wood into a gas, and it is the gas that burns. Therefore, the presence of too much water inhibits a clean burn, the heat cannot gasify the wood fast enough, and the fire smolders.
Another reason properly seasoned wood is that too much moisture causes excess pollutants to be sent into the atmosphere. It will also cause creosote to build up in your chimney and your wood burning appliance. This can cause chimney fires and make it impossible to enjoy the fire because your glass will be covered in black creosote and ash.
Properly seasoned firewood improves combustion, so the fire burns clean, and prevents the buildup of creosote. Creosote is the cause of chimney fires, and it also prevents your enjoyment of the fire because of the buildup on the glass. So be sure to properly season you wood for your fire enjoyment!
The Best Varieties of Wood to Use as Firewood
It is often thought that the type of wood is incredibly important, but in reality, the variety of firewood does not make much of a difference. All species of wood have remarkably similar Btu potential per pound of wood.
Oak is often thought to be one of the best woods to burn, and it is if you are looking to burn the least amount of volume of wood. However, per pound, oak has a similar Btu output as birch, maple, or even softwoods.
Avoid Kiln Dried Lumber in the Firebox
Kiln dried wood will burn faster because there is not as much, or any water. We want a hot fire, but not one that is as hot as possible. If it is too hot, then the heat will be so intense that it will not be sufficiently absorbed by the masonry. This will lead to excess heat going up the chimney and a loss of efficiency.
Secondly, because there is not the water in it to “slow” the burn, it will try to burn more quickly than the oxygen that we supply from our air supply door can keep up to. The fire will behave like it is oxygen deprived, and it will belch black smoke.
Split to Standard Cordwood Size
We design the fireboxes to burn standard cordwood. There is an averaged amount of air needed that we supply for. The proper sized wood and moisture content makes it so that the oxygen necessary is available for the burn. If you were to split all of your wood into kindling, and pack 50 pounds of kindling into the firebox and light it, there would be too much surface area. All of that surface area would try to gasify for the burning and you would have an oxygen deprived burn.
This is the same kind of thing that happens with kiln dried cordwood. There is not enough water to keep the gasification process slowed to a rate that the oxygen can keep up with, and if it could the fire would be far too hot to be efficient.
Hardwoods Take Less Storage Space
One factor to consider is that when it comes to storing wood it is easier to store hardwoods because they take up less space. But strictly speaking, whether you are going to burn pine or oak, pound for pound they have the same Btu potential.
Regardless of whether you are burning softwoods or hardwoods the important thing is that you take the time to properly season the wood.
What is Properly Seasoned Firewood?
Properly seasoned firewood requires advanced preparation that will pay off when the weather turns cold. Ideally, you will be harvesting your firewood in the early spring for the following season. Let us explore exactly how to season firewood correctly.
Cut, Split, Stack, and Cover Firewood
The right way to prepare firewood means that you cut it to the desired length, split it, and stack it under cover to protect it from the weather. Storing your cut and split wood under cover is extremely important. Wood that is exposed to rain or snow will absorb moisture. It needs to be covered.
Time Required to Season Firewood
Properly seasoned wood has a moisture content of 20% or less. To get this level of moisture content, it takes a minimum of 6 months in dry storage after the wood has been split and stacked. A more conservative estimate is to store the wood for a year before using.
If you are going to prepare wood for the coming winter, you need to finish preparation no later than the end of April. It is wise to check the moisture content with a moisture meter because it may not be finished, especially oak. Red oak can take up to two years to season! Most other woods will be ready in a year. Under ideal conditions some wood may be seasoned and ready to burn in as little as 6 months.
Protect Firewood from Moisture
Proper wood storage protects the wood from moisture, but still allows air flow around the wood to promote drying. The best method for storing firewood is in a woodshed. Other methods may work provided they allow for air movement and prevent moisture from reaching the stack.
Be careful when covering wood with a plastic tarp. Plastic will not allow the moisture to escape properly and keep the area under the plastic humid. This can lead to the growth of mold or mosses on the wood. Organic growth on your wood is an indication of moisture, and that will keep your wood from burning efficiently.
Learn everything you ever wanted to know about harvesting and storing firewood here.
A Note on Potential Pollutants
Wood burning devices have earned a bad wrap when it comes to polluting the air. You may be interested in this publication for policymakers to learn more.
Summary for Policymakers The Northeast States for Coordinated Air Use Management (NESCAUM) in collaboration with the Alaska Department of Environmental Conservation (ADEC) conducted a review of the US Environmental Protection Agency’s (EPA’s) program to certify that new wood stoves and central heaters meet air pollution standards.
Masonry heaters burn incredibly hot for a short period of time, producing significantly less pollutants than other wood burning options.
Baking and Warming Your Home with Wood
Carefully consider what your goals are before selecting and installing a wood burning appliance in your home. It makes sense to select one that will perform well for many years, is highly efficient, and that can warm your home safely during a power outage.
One of the great assets to a Temp-Cast masonry heater is the built-in oven option. It is an amazing way to cook your food all winter long without using any additional fuel.
Contact me at Temp-Cast and let’s explore how this ingenious masonry heater might just might be the perfect addition to your home.