Ways to be Fuel Smart: Fast Facts about Heating with Wood

Home | Insulation | Conserving Energy

Heating | Books | Links

Historically, when prices for conventional fuels rise, people consider the possibility of burning wood at home. Wood as a fuel source has advantages and disadvantages.

Advantage: Wood is considered a renewable resource. If we plant and harvest it wisely, we can keep using wood without using it up. Getting that down to personal terms, a well-man aged woodlot no bigger than 12 acres will provide enough fuel for an average home, every year, forever.

Disadvantage: We know that in many parts of the world wood is extremely scarce. Poor planning and harvesting too frequently can deplete this vital natural resource.

Advantage: Wood as a source of heat can feel so good. It’s toasty and homey to sit around a woodstove. After being out doors on a cold day, nothing feels better than sitting next to a warming fire.

Disadvantage: Wood smoke can contain pollutants that reduce the quality of the air we breathe. Some cities and towns now limit the number of households that can have woodstoves. When buying a woodstove, ask about emissions and efficiency. The catalytic and other stoves of the past 20 years burn much cleaner than older models.

Advantage: Advances in woodstove technology include wood- pellet stoves, which are more convenient to operate and burn more efficiently with lower emissions. These stoves have a longer burn time and are easier to load and control. The fuel for them is usually waste wood that is made into easy-to-handle pellets.

If you have a fireplace, you no doubt enjoy sitting in front of a wood fire. You need to know that a fireplace is an inefficient way to burn wood and requires some managing just to give you a net heat gain. We’ll explain that a little later. Even so, a fireplace is a start.

In fact, a fireplace can be a fine start, because it means you have a chimney — one of the essentials for using wood as fuel.

A number of good woodstove models are designed to fit on your fireplace hearth and be vented up the fireplace chimney, so if you get at all serious about wood fuel, a fireplace can be a substantial beginning.

It can be helpful to know which are the better kinds of wood to burn. A hickory log, for instance, has locked within it twice as much potential heat as a butternut log of exactly the same size. When looking for fuel efficiency, this kind of knowledge can be very useful, and it’s outlined in the paragraphs that follow.

Much wood-burning wisdom goes back to the very dawn of civilization, because wood was humankind’s original fuel and , in fact, was the dominant fuel in use in North America as recently as 150 years ago. The tools, equipments and know- how of using wood fuel are all readily available, both because there are many homes where wood has always been used for heating, and many more that are sprouting shiny new chimneys.

Incidentally, I don’t plan to get into the details of wood- stove installation and maintenance, which is the province of other volumes, but I feel compelled to offer one caution. By its very nature, an open fire in your home can be dangerous, and there are particular hazards inherent in the chimneys of fire places and woodstoves.

Before installing a stove get some expert advice, or at least start with an authoritative book on the subject. Be sure to con tact your building inspector or local fire department for guidance. I’d hate to think that your reading of this section might create an enthusiasm that would place your home in jeopardy.

With a conventional woodstove, you’re going to get some exercise. At the very least, you’ll be carrying logs to the fire place, or sticks to the stove, and later putting the ashes into a bucket or scuttle for removal. You may even be fully managing a woodlot and felling your own trees. How much effort you put into your woodstove will depend on how much time you have and how much energy you have to give.

Every part of the process you do yourself will save you money. Where I live, for instance, a cord of wood split, delivered, and stacked in yard or garage costs approximately $100. It takes about seven cords to heat my house for the winter, so getting my fuel that way could cost $700 to $1000, which would be cheaper than running the oil burner. However, I can cut the same wood on my own land for nothing.

I have bought wood already split; I have bought wood ready for splitting; and I have cut my own. What I do depends in part on my available time when the woodpile needs replenishing. For a cheery fireplace, or a complete wood heat sys tem, you’ll likely make your decisions that same way.

Open up the damper and fire the kindling. Here we go!

A More Efficient Fireplace

You have a fireplace? Let’s start there.

A fireplace is likely to steal more heat than it delivers. The necessary draft up the chimney pulls warm air from the room, resulting in a net heat loss. This is particularly true as the fire is dying down, radiating less heat into the room but still having a good draft up the chimney.

• Your fireplace should have a damper, a gate that closes off the chimney at the throat of the fireplace. As soon as a fire is out and no longer smoking, the damper should be closed. An open fireplace damper will drain heat from a house as fast as an open window.

• Glass doors on your fireplace will let you see the flames while minimizing the heat loss from the room. They are particularly valuable after you’ve gone to bed, because they cut off the heat loss from the room as the fire dies.

• Some woodstoves are designed to sit on your fireplace hearth and be vented up the fireplace chimney — an effective idea. Some models have an additional door on the side for firing up the stove while the front doors are shut. Some also have an interior baffle system for greater fuel efficiency. Some allow you to open the front doors and enjoy the open fire. Make sure to use a screen to prevent embers from flying. At all other times, be sure to close the doors.

• If you’re planning to build an open fireplace, consider including a sheet metal Heatilator box. It will draw in cool air from the floor, warm it around the firebox, and send it warm into the room through vents. By combining it with a glass screen, you can improve your heating efficiency relative to an ordinary fireplace.

• Another fireplace accessory is a grate that enhances airflow into and out of the fireplace, thereby increasing heat flow into the room. These grates come in several sizes to accommodate different fireplace designs and can be used with glass doors. A small fan with thermostatic controls can help regulate the heat.

• The greatest heat loss from a fireplace is during the night, after an evening fire, when the damper must remain open to let out the smoke. Caution: A slow-burning wood fire is a potential source of dangerous carbon monoxide. Make sure your fire is cold before you close the damper. Covering the fireplace opening with a fire-rated material will cut off the flow of heated air up the chimney.

Wood Facts

The chart below shows the actual fuel values in various types of wood. The differences are significant. In some parts of North America the fuel woods of lesser value are more readily available, and everywhere pine is easier to cut and split than beech. Get acquainted with what burns best and longest among the woods available where you live.

CHOOSING FIREWOOD

THE GOOD WOODS

Tree

BTUS per cord (in thousands)

Shagbark Hickory

Black Locust

Ironwood

Apple

Rock Elm

White Oak

Beech

Yellow Birch

Sugar Maple

Red Oak

White Ash

24,600

24,600

24,100

23,877

23,488

22,700

21,800

21300

21,300

21,300

20,000

SECOND-CHOICE WOODS

Tree

BTUs per cord (in thousands)

Black Walnut

White Birch

Black Cherry

Tamarack (Larch)

Red Maple

Green Ash

Pitch Pine

Sycamore

Black Ash

American Elm

Sliver Maple

19,500

18,900

18,770

18,650

18,600

18,360

17,970

17,950

17,300

17,200

17,000

HARDLY WORTH CUTTING

Tree

Red Spruce

Hemlock

Black Willow

Butternut

Red Pine

Aspen (Poplar)

White Pine

Basswood

Balsam Fir

BTUs per cord (in thousands)

13,632

13,500

13,206

12,800

12,765

12,500

12,022

11,700

11,282

Here’s a fact worth knowing — the actual dimensions of that mysterious measurement, the cord. Many homeowners don’t know that a full cord is 4 feet x 4 feet x 8 feet. Because of this, the wood seller can often get away with selling what he loosely calls a cord but what is really precisely what he felt like throwing on the truck that day. Knowing can be saving.

Burning fresh-cut wood will deposit creosote in your chimney and can result in a chimney fire. You’ll run less risk and wood that has been cut and split at least 6 months. You can be sure you’re burning dry wood when your home supply is stacked at least 6 months before you intend to use it.

Stacking wood in the side yard? Put down parallel poles with the bark still on and stack on top of them. Eventually they will rot, but that’s better than having the ground rot eat away firewood into which you’ve put the work of cutting and splitting. A covered pile will dry faster.

Split Your Own Wood

• Think about buying your firewood un-split. It will be less expensive. Good exercise, too.

• Splitting wood on the concrete floor in your basement or garage, or on a brick or stone hearth, is a sure way to ruin your axe, no matter how careful you think you can be.

• Some woods don’t split well. Birch and maple split beautifully. A piece of gnarled cherry is a tough one. Choose your fire- woods carefully if you’re going to do the splitting.

• Don’t try to split long sections of wood before cutting them into stove or fireplace lengths. Short lengths split much more easily.

• For splitting firewood, a slightly dull axe is better than one with a razor edge. There’s not only less risk of cutting your self but also less chance of getting the axe stuck in the wood.

• Hold the axe handle as near to the end as you can and take a full swing. The momentum of the weight of the axe-head, instead of just your muscle power, will be doing the work.

• Use an axe whose head tapers out to a flat wedge. A slender head is more likely to get stuck in the Jog. A double-bitted axe with two blades is not designed for splitting wood. It is dangerous to use and too slender for splitting well.

• For splitting big, knotty lengths of wood, a maul or a sledgehammer and some splitting wedges will do the trick. A maul looks like a sledgehammer with one side tapered to an edge. Splitting wedges look like fat slices of pie made from tempered steel.

• If you’re going to split a year’s supply of fuel wood for your home, consider a power log-splitter. You can probably get one at the tool rental shop in your town. Follow directions carefully.

• If you have a big, fat stump in your woodpile that looks as if it isn’t going to split easily, don’t bother trying. That’s just the one you need for a chopping block.

• For sawing trees or full-length cordwood into burning lengths, a chain saw will do the fastest job. Among the hand tools, a bow saw or a bucksaw is the best choice. Cutting firewood with a carpenter’s handsaw will wear you out, and chopping it to length with an axe is something you should try only if your doctor recommends an excess of violent exercise.

• Everyone misses a stroke now and then when splitting wood. Gather up those chips for starter kindling.

• Birch logs are pretty just as they are sawed from the tree, but they must be split promptly. Birch-bark is almost completely waterproof (the native Americans made canoes from it), and unless you split it, the inside wood will rot quickly and get “punky,” rendering it useless for firewood.

All of what has just been said about preparing wood for burning applies to stoves as much as it does to fireplaces, and a good woodstove is many times more fuel-efficient than a fireplace at its best.

The Helpful Woodstove

When choosing a woodstove, consider one with a flat top where a pot of water can simmer during the day. This will add needed humidity to your room, and you’ll have water for cups of tea or coffee without starting up the cooking range.

Some woodstoves burn wood more efficiently than others. Your stove’s workmanship and design are important features that affect efficiency. Make sure your new woodstove has a catalytic combustor or meets Environmental Protection Agency (EPA) emission standards. This increases the efficiency and reduces the pollutants sent into our air. All new stoves are now tested and rated for seasonal and combustion efficiency. Compare efficiencies when purchasing this major appliance. and remember to make sure your stove is correctly sized for the space it will need to heat.

If you’ll be using an older stove, look into installing a catalytic add-on to increase efficiency and reduce emissions. If you have a new stove in your plans, consider a wood-burning cookstove. Some models are very attractive, and all have the advantage of saving on kitchen fuel as well as providing room heat.

When starting a stove fire, use rolled paper, slender sticks of kindling, and one or two pieces of split wood. Open all the drafts, get a good fire going, and add more wood when this “starter set” has become a bed of coals. Then adjust the drafts and add more wood as needed when each firing has been reduced to hot coals.

In a well-made, cast-iron woodstove, a few sticks just smoldering on a bed of hot coals will still put out a lot of warmth, and they’ll quickly spring to a blaze even after several hours as soon as you open the drafts and add a little oxygen from the outside.

A woodstove is most efficient when installed near the center of the house, on the first floor, or down in the cellar. A stove in the cellar will help keep the water pipes from freezing in a winter emergency.

You can always start a stove fire with paper and well-split kindling. If you can’t, check for blockage in your stovepipe draft. Do not use lighter fluid, gasoline, or other flammables to start an indoor stove fire.

You can bum rolled newspapers in your woodstove. One stick of firewood with two “newspaper logs” makes a good combination, and laying this fire is easier than taking the old papers out to be recycled.

If you are using a woodstove regularly, two wood-boxes are a good idea: a larger one for the day’s fuel supply, and a smaller one to hold kindling splints. Neither woodbox should touch any part of the stove. Dry wood ignites very easily, so keep any woodbox 36 inches from the stove.

It’s tempting to use your woodstove as a trash disposal. Don’t. It’s an unnecessarily risky way to try to save money. In a fireplace or stove, paper trash and other flammables, like Christmas tree branches, burn too hot and with flames big enough to cause a chimney fire. Recycling your paper trash is a much better idea. Artificial logs made of pressed sawdust impregnated with wax or other artificial compounds can also be dangerous. If a fire gets out of control for any reason, artificial logs are almost impossible to extinguish.

A brick wall behind your stove will not only make it safer to operate but will also hold and radiate heat, multiplying your stove’s advantages. Be careful. Bricks one at a time may not seem particularly heavy, but even a modest brick wall can weigh several hundred pounds. Be sure your floor is braced underneath enough to carry the load of wall plus stove.

Someone taking down a dead tree in the neighborhood may create an opportunity for you. Check with the tree crew. Any part of the leftovers that they’ll put in your yard, or let you haul away, can be either kindling or firewood.

Better Wood Burning

Here are some ideas that may make your wood burning easier as well as safer.

• Don’t have a woodstove exhaust into a flue already in use. Each fire must have a flue of its own.

• Yes, it is possible to open the drafts on a wood fire and get it so hot it will warp the grates and even the top of your stove. This is most likely to happen when you’re trying to get a woodstove hot too fast. Take it easy. Your stove will get up to its best heat in due time. Don’t try to force it.

• Coal burns much hotter than wood. Don’t burn coal in a stove designed for wood.

• Clean your chimney at least once a year to keep creosote from building up. The frequency of cleaning depends on the amount of wood you burn and how well it is seasoned. Check the Internet Yellow Pages for chimney-sweep services.

• A smoldering fire can lead to increased creosote buildup.

This is more likely during the swing seasons — spring and fall — when you don’t want an extremely hot fire. A controlled hotter burn from time to time will help reduce this buildup.

• Install a magnetic temperature gauge on your flue pipe to help monitor the temperature of your fire.

Insulated, double-wall stovepipe is your best bet for an outside chimney. There will be less moisture condensation than with a single-wall pipe and therefore less buildup of the flammable carbons and tars that cause chimney fires.

• A heat exchanger for your woodstove flue pipe will increase the heat output. There are several designs which extract heat from the pipe before the smoke gets outdoors. Some have a fan to blow the trapped warmth into the room.

Final Thoughts on Heating with Wood

Your house design may allow for a small access hatch between the woodpile and your stove or fireplace. That will eliminate carrying wood in from outdoors, with the resulting opening and closing of doors.

• Spray a light mist of water on the ashes in stove or fire place before you remove them to minimize the “fly ash” spreading around the room. Recycle a “spritz” bottle for this job after it is emptied and well rinsed of its previous contents.

Next: Traditional Wisdom That Really Works

Prev: Rake in Savings from Your Garden

Top of page  All Related Articles     Products   Home