Few cold winter evening experiences are as pleasant as sitting before the woodstove soaking up the warmth of a fire. That heat is essentially solar energy captured by the tree through photosynthesis on past summer days and released by fire in the dead of winter.
There are plenty of good reasons to consider wood heat and lots of reasons to forget it. Heating with wood is a lifestyle that requires elbow grease to cut, move, split, and stack firewood. Wood needs to constantly be fed into the stove and ashes must be removed every couple of days. Although attractive and cozy, burning wood brings pieces of bark and dirt into the home. These can be downsides, but many people love to work with wood, and cutting and splitting are pleasures, not chores. Wood heat can also save heating money, especially if the fuel comes free.
We have two woodstoves at Winding Pathways. Years ago we ditched our romantic but inefficient fireplace and added a stove. They are much more efficient than fireplaces, meaning that more of the energy in a chunk of wood ends up making a room comfortable and less goes up the chimney.
Now is a great time to plan for wood heat for next winter. It takes time to buy a stove and have it installed. To lay in next winter’s wood supply nearly a year in advance is critical.
The wood of living trees contains water that must be removed before it will burn well. Cut and split firewood stacked in a dry breezy place takes six months to a year for evaporation to remove enough water to transform it into efficient fuel. Late winter is a great time to process wood for next winter. We like to have all of next winter’s wood ready by the end of this March.
Wood is solidified sunshine mixed with minerals. Not all wood is created equally. The energy contained in a chunk is directly proportional to its weight. Dry hickory, for example, is about twice as heavy as the same size hunk of cottonwood and contains double the energy. To learn the heat value of different tree species simply Google Sweep’s Library Firewood BTU Comparison Charts. This chart lists heat values of wood by both alphabet and heat (BTU) value.
Utah State University’s link includes heat value, ease of splitting, smoke emissions, how much a wood sparks and fragrance.
For example, a cord of Maple (Sugar) weighs 3740 pounds and contains 23.2 million BTUs. In contrast a cord of Cottonwood weighs 2040 pounds and contains 12.6 million BTUs of energy. This relationship shows a homeowner would need process and store about twice as much Cottonwood as Sugar Maple to yield the same amount of heat.
Wood is usually sold by the cord or 128 cubic feet. That’s a stack eight feet long, four feet high and four feet deep. Hickory, black locust, white oak and sugar maple are the heaviest common woods of eastern and central North America. Cottonwood, basswood, aspen and most pines and spruces are the lightest. Elm, cherry, silver maple, hackberry and ash fall in between. In a normal Iowa winter we burn about three cords of a blend of oak, black cherry and maple. We’ve burned our share of “poorer” woods like cottonwood and box elder because it was available and we were short of heavier species. Lighter wood generates wonderful heat. It just takes a lot more of it than if we had hickory or oak. Wood is our main, but not only, heat source. We have a natural gas furnace and installed a gas insert into the old fireplace. Both work well and keep the house warm when we go on winter trips and are not around to feed wood into the stoves.