PHOTO: Jan Faukner/Shutterstock
Dave Boyt
January 16, 2020

Trees are the ultimate solar collection and storage devices. Think of them as solar collectors (leaves) that cost nothing, manufacture themselves and integrate with a safe, reliable storage system that holds its charge for years.

The solar collectors and any unused wood automatically decompose into a beneficial soil amendment as new ones take their place. Why not put these solar collectors to work heating your home? Let’s take a look at how finding, splitting and storing wood for burning can heat you during cold winter days.

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Early Days

There have been a lot of changes since I first cut a winter’s supply of firewood back in 1981. Back then, hydraulic firewood splitters were a luxury I could only admire from a respectable distance before picking up my splitting maul and heading for the woods.

The McCulloch “Mac 10” chainsaw I had was finicky, refusing to start for days at a time, but had plenty of power once it started and the smoke cleared to the point where you could actually see the log. When the blade dulled to the point where it would no longer put out even a fine powder, I’d pull out the file and try to restore some semblance of an edge, and maybe take a couple of swipes on the raker teeth, if I thought of it.

Personal protection equipment (hard hats; face, eye and hearing protection; chaps; and steel-toe boots) was also unknown back then, and to this day, I have a constant ringing in my ears (tinnitus) from hours of exposure to the 115 decibel roar of the saw at full throttle.

(If you plan to cut wood and lack the equipment and training to use a chainsaw, by the way, check with your local chainsaw dealer. Also watch some chain saw safety videos on YouTube.)

As a sawmill owner, heating my home with firewood is a natural. Today I use a modern chainsaw that starts easily, up-to-date safety apparel and a hydraulic log splitter.

Although the old timers say that the winter’s supply of wood should be cut and split by the Fourth of July, it always seems I delay cutting wood for burning until well after the first frost. I not only cut and split the wood in subfreezing weather, but I also spend a great deal of time trying to coax a reluctant flame from wood that is nearly half water by weight.

stacked wood for burning
James R. Martin/Shutterstock

Firewood Factors

There are three factors that determine how much heat you get out of a stack of wood: the volume, moisture content and species. If you buy wood for burning, make sure you know the following:

  • What species are you getting?
  • When it was cut?
  • What’s the length?
  • Is the price is per full cord or face cord?
  • Can the seller deliver and stack the wood?

The biggest demand for seasoned firewood is in the winter, so you can save yourself some money if you plan ahead and purchase green wood in the spring and season it yourself. You will have the peace of mind that it’s taken care of. Plus, there will be no issues with moisture in the wood when it comes time to burn it.

In the U.S., the only consistent measure of firewood volume is the cord. This is 128 cubic feet of wood, typically stacked 4 feet deep by 4 feet high by
8 feet long.

A face cord is a stack of wood 4 feet high by 8 feet long by whatever the length of the firewood is. For example, a face cord of 16-inch firewood is one-third of a full cord. A face cord of 24-inch firewood is half of a full cord.

A “rick” is generally the same as a face cord, but there is no standard definition. So if you buy or sell wood by the rick, be sure everyone involved agrees to the amount. Some outfits might sell wood for burning by the ton. But if the wood is freshly cut, you’ll be buying a lot of water.

Moisture in wood is a complex issue, but for wood for burning, drier is usually better, as anyone who has tried to heat with freshly cut and split (green) wood will attest.

The first issue is the amount of heat in the wood, which combusts at around 450 degrees Fahrenheit. Before that can happen, it has to boil off any moisture, which occurs at about 212 degrees.

The energy required to remove the moisture can be over half the heat in green logs. In other words, once you do get the fire going, it will only give you half the useful heat as seasoned firewood.

The other downside to heating with green wood is that the poor combustion leads to rapid tar and creosote build-up in the chimney. This can choke off the chimney so that it doesn’t draw in air, making the wood even less efficient. More importantly, tar and creosote are highly flammable, and when they ignite—as can happen when you burn too much paper at once—you will have a flue fire.

I have had that happen once, and once was enough! All we could do was watch helplessly as 8-foot flames shot up from the chimney in an uncontrollable inferno. Fortunately, the chimney contained the blaze with only minor damage to the masonry.

But in 2016, roughly 25,000 chimney fires were reported, destroying more than 100 homes and causing over $125 million in damage.

Density

The best indicator of the heat value in seasoned firewood is density. A cord of a dense species, such as oak, hickory, hard maple and ash, contains roughly the energy equivalent of 200 gallons of gasoline. Elm, soft maple and birch contain the energy of about 150 gallons of gasoline, while lightweights such as Aspen, cottonwood and pine contain the energy of around 100 gallons.

In the Missouri Ozarks, where I live, Osage orange (hedge) is the top-rated firewood at the equivalent of 275 gallons of gasoline per cord. But it’s expensive and must be used carefully as it can overheat a stove—as I learned one cold winter night. The Osage orange burned so hot, the stove was actually glowing in the dark. The following morning, there was a big crack in the cast iron top.

The Utah State University Forestry Extension lists a number of species of wood by heating value.

Cutting your own firewood gives you control over the species, size—width as well as length—and seasoning time. For example, you can cut a variety of size and species to serve as everything from kindling to overnight logs. Pine, walnut and sycamore make great fire starters, because they catch fire easily and burn hot and fast. I like to split ash, oak and hickory into larger chunks, because they will hold a fire overnight, leaving a good bed of coals to start the fire the next morning.

While I do get a great deal of satisfaction from cutting and splitting firewood, it always seems to be a mad scramble to get the job done before cold weather sets in.

As a source, you might check with tree services and sawmills. Sawmill slabs are cheap and many sawmill operators will load bundles of slabs on your trailer. You can usually cut through a bundle pretty quickly, and the wood splits easily, even by hand. But there is typically a lot of bark on sawmill slabs, so they don’t have as much heating value as solid wood.

Fuel Savings

Your fuel savings for the first year will be pretty much offset by the purchase of equipment:

  • Chainsaw with an engine in the 50cc to 60cc displacement range and an 18-inch bar—around $500
  • Hydraulic splitter—$800 to $1,200
  • Chaps and logging helmet—roughly $150
  • A used trailer—approximately $200

Of course, you should figure in the value of the time you spend working with the wood. Is it worth it? Let’s crunch some numbers to see what some of the competing sources of energy would cost. Based on the heating value of a full cord of seasoned white oak with a heat content of 29.1 million BTUs, here is the equivalent amount of other heat sources and their cost.

Type Usage Measurement Per Unit Cost Total
Electricity 8,529 kilowatt hours $0.13 per kilowatt hours $1,134
Natural Gas 27,700 cubic feet $11 per thousand cubic feet $304
Propane 318 gallons $3 per gallon $954

 

My home, for example, goes through about 2 1⁄2 cords per year. Propane would cost us about $2,385 per year.

Equipment (fuel, maintenance, equipment replacement after 10 years) is about $180 per year. Time invested per year (including equipment maintenance, processing firewood, feeding the stove, taking out ashes, etc.) is 40 hours per year, so I’ll give it a value of $800. Rounding it to $1,000 per year, that still saves $1,385 on my heating bill. Even purchased wood for burning at $240 per cord is about a quarter the cost of propane.

Stacking Tactics

Stacking wood is an art and science that you will learn with experience.

Most people stack firewood in straight rows about 4 feet high. This has the advantage of giving a good visual indication of how much wood you have. A steel fence post every 8 feet helps hold the stack in place.

If you stack wood in multiple rows, set them about 2 feet apart for good air circulation.

Sheets of metal roofing weighted down with wood will speed up the drying process. It will also keep snow off in the winter so you’ll always have dry wood. A cheap alternative is to let the wood dry in the open and cover it with a tarp to keep the snow off in the winter.

We stack our wood in traditional circular holzhaus (German for “wood house”). It takes a bit of practice, but once you get the knack of it they build quickly and have good air circulation for drying wood. Plus, you can throw oddball pieces in the center. We build them 6 feet in diameter and roughly 41⁄2 feet high, which is very close to a cord per stack.

Of course, you could always stack your firewood in a wood shed … when you get around to building one! I’ve been meaning to build a wood shed for the last 20 years, but somehow have just not gotten around to it.

The old adage that firewood heats you twice—once when you split it, and again when you burn it—is much less appealing if you cut and split your wood for burning in the winter during the summer. But just seeing a pile of wood, knowing that whatever else happens, at least you’ll be warm this winter? That does warm the heart!

 

This story originally appeared in the November/December 2019 issue of Hobby Farms magazine.

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