Wood is looking good these days when it comes to home heating. The supply is local, the price is relatively stable (at least compared to oil), and the carbon in wood does not contribute to climate change (since it’s already in the biosphere.) But the recent influx of homeowners who’ve never burned wood into the firewood market has raised the age-old question: how much wood is there, exactly, in a cord of firewood?
The simple answer is 128 cubic feet. The exact answer is an 8-foot pile of 4-foot-long logs that are stacked 4-feet high. The real-life answer is that no two cords are alike.
The problems begin because almost nobody burns firewood in round, four-foot lengths. Job one for either you or your firewood supplier is to cut the 128 cubic feet of wood to stove length (usually 16-, 18-, or 20-inch) chunks. This process is going to increase the pile’s volume since the space between the cut ends is going to make the stack wider than the original four feet.
The next step is to split the stove-length chunks into manageable pieces. Splitting the wood is going to reduce its volume because the knots and other irregularities that were creating air space between the round logs are going to be reduced in size and packed tighter in the pile after they’re split. Unless, of course, the initial roundwood was extremely smooth, in which case splitting the wood will increase its volume.
Of course, the first person to actually measure the volume of wood in the cord is likely to be you, the homeowner, as you stack it into your woodshed. The person who initially sold the firewood “log length” made an estimate based on how many trunks can fit on the truck. Then the person who sold the wood “cut, split, and delivered” made an estimate of how deep the pile has to be in the bed of the dump truck to equal a cord. Many firewood purveyors use a rule-of-thumb of 200 cubic feet of piled wood, or two loads thrown into the bed of a full-sized pickup truck, as the equivalent of one stacked cord.
Adding to the confusion is the term you’ll hear sometimes, the “face cord,” which is defined as whatever the firewood dealer wants it to mean, usually being a stack of stove wood eight feet long by four feet high. If the stovewood is 16 inches long, the face cord is equal to one third of a regular cord. If it’s 12 inches long, it’s a quarter cord. Either way, it’s a fraction of a true cord.
Then there’s the dryness factor, since wood will shrink between 2% and 10% across the grain as it dries. How can you tell if the wood you are buying is “green” (wet) or “seasoned” (dry)? Green wood in general is heavier, has tight bark, and does not have any splits or cracks in it. Seasoned wood is lighter, often has loose or missing bark, and is cracked or “checked” from drying.
In short, a perfectly legal cord of wood – 128 cubic feet of green roundwood, four feet long, bark attached, casually piled – could conceivably be reduced to 90 cubic feet by the time it’s dried, debarked, cut and split, and neatly stacked under cover in your woodshed.
The key for the consumer is to know how much they’re being charged, and for what. In other words, “Trust, but verify.” A price of $350 per cord might be a relative bargain if that cord ends up filling 150 cubic feet in your woodshed, especially if it’s a high-BTU wood, such as oak, hard maple, or hickory. These species pack 20 percent more BTUs than cherry, paper birch, or soft maple, for example. Pay $150 for what’s really a 16-inch face cord, and you’ve been ripped off, regardless of the species.
The bottom line is that, when heating oil is selling for $4.00 per gallon, the equivalent BTUs in a cord of seasoned, mixed species hardwood are worth $557.08. If you’re paying less than that for 128 cubic feet, you’re ahead.