Heating with wood can actually be the most sustainable way we have of keeping our homes warm. Wood, of course, is a renewable resource as long as we harvest it responsibly and act as stewards of the forests. Rather than chopping down living trees, there are any number of fallen trees, fallen branches, and coppicing species (trees that can be cut and regrow from the stump) that can be used for acquiring firewood without killing a single tree.
Even better, nowadays there are an assortment of high-efficiency wood stoves that get the heating done with much less fuel wood than was once required. The other benefit to these high-efficiency stoves is that they cause much less pollution, burning up the wood entirely rather than sending a lot of smoke into air. Many people are beginning to lean towards wood heat as a supplement to conventional HVAC systems or as a means of self-reliance.
All that said, a lot depends on the firewood being put into the wood stove or fireplace. Good firewood isn’t gotten by simply cutting down a tree, chopping it up and burning it. The crux to producing heat with wood is using seasoned firewood. Seasoned firewood burns hotter, more easily and more safely than “green” or “wet” wood.
Why Just Any Wood Isn’t Good
Essentially, wood needs to dry out before it’s burnt. When a living tree is chopped down or a live branch is blown out of a tree, it has a lot of moisture in it. The water in the wood is both free (stored in the tiny, open cavities between cells) and molecular (stored in the cells). The free water evaporates off first, and it accounts for about 70% of what’s there. That leaves a moisture content of 30% in the wood. Ideally, seasoned wood has 20% (or less) moisture content. So, there needs to be some time for the molecular water to evaporate as well.
The reason this is important is because wet wood doesn’t burn efficiently. A lot of heat produced by the fire goes into boiling the water out of the wood so it can burn. This makes it a lot harder to keep burning, and it means the fire is not heating the house but the water. Green wood also produces a lot more smoke, causing air pollution. The moist smoke catches in the chimney, causing creosote buildup, which in turn can cause chimney fires. In other words, seasoned wood is much better.
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How to Season Firewood
The good news is that seasoned firewood is just the same wood as green firewood, only it has been given time to dry out. Generally, the minimum amount of time for seasoning is about six months, so cutting firewood in the spring or early winter (when trees are dormant they have less moisture) could supply for autumn fires. For some woods, particularly large pieces or hardwoods, a year or more of drying might be ideal. The point is that, when it comes to firewood, it’s good to have a little forethought.
And, there are a few things that can help to make the seasoning go well:
- Split the wood. It will dry it faster because air will reach more parts of it.
- Lift the wood. It won’t wick water from the ground, and it’ll also be protected from bugs and fungus. Plus, air will move beneath it, which helps with drying it out.
- Stack the wood in single rows. It allows air to flow around it better, and the air pulls moisture out of it. Squarish pieces of wood dry better when stacked crisscrossed with small space between each piece.
- Cover the wood with a roof. A roof keeps rain and snow off of the wood, so it dries out faster. However, don’t cover the sides of the pile as it prevents the sun and wind from helping the process.
- Locate the wood in a sunny spot, preferably with a breeze. The sun will evaporate the water, and the wind will pull it away.
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When Seasoned Wood Is Ready
If we are getting very technical about the moisture content of the wood being 20%, there are moisture content meters than can be used to measure this. Regardless, logs will have different moisture levels in different spots, such as the ends versus the middle. For those who like gizmos, meters can be purchased at hardware and home improvement stores for about $20-$40.
The less gadget-y way to tell is to use the senses to provide some clues.
- Sight: Cracks will begin to form at the end of logs due to the shrinkage from losing moisture. The bark should also fall off and be noticeably loose. The color will dull, typically into a cream, yellow or gray hue rather than bright white or green.
- Smell: The sappy smell of the wood should be gone. If scraped or split, it shouldn’t have that freshly cut aroma anymore.
- Sound: Once the wood is seasoned, it has much less moisture, so when two pieces are knocked together, they’ll sound hollow. Wet pieces sound dull when knocked together.
- Feel: With added moisture comes added weight, so seasoned pieces are detectably lighter than green wood.
- Taste: Maybe not.
Once the wood is seasoned, it will be a pleasure to burn, and it can provide inexpensive, clean, renewable energy for heating in the wintertime. Then, using the ash from it will make the winter garden greener as well.
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