Keep these tips in mind while seasoning firewood to heat your home.
Want to heat your rural home without gas or coal? In Wood Heat (Firefly Books, 2014), author Andrew Jones provides a useful guide to using wood to heat your home. Jones dissects the environmental and economical upsides and downsides of heating with wood while providing advice and instructions that are necessary to help you successfully produce enough energy to keep your home warm during the winter. This excerpt, which discusses drying and seasoning firewood for use, is from Chapter 2,”Wood.”
You can buy this book from the MOTHER EARTH NEWS store: Wood Heat.
Tips for Properly Seasoning Firewood
Wood is essentially a mass of tiny long tubes, or cell cavities, that run the length of the tree. Moisture exists both as “free water” in these cavities and as molecular water that is locked in the cell walls. When a tree is felled, the slow process of drying begins, and the free water is the first to evaporate. Once the free water evaporates, the moisture content of the wood is around 30 percent. This is called the “fiber saturation point.” After this, water begins to leave the cell walls, and the wood starts to shrink and crack.
For optimal burning, firewood should be dried, or “seasoned,” until its moisture content is less than 20 percent. Firewood with a moisture content higher than that may eventually burn, but it is devilishly hard to light and just as hard to keep burning. Also, your new high-efficiency wood-burning stove or furnace is guaranteed to perform sluggishly as it struggles to burn freshly split, or “green,” firewood—much of the heat and energy content produced are wasted in drying the wood’s excess moisture. Just as important, the stove does not burn the tars and creosote in the smoke produced by the fire, and they end up lining the inside of your flue pipes and chimney. They also blacken the glass windows of your wood-burning appliances and produce a lot of blue-gray smoke, fouling your house and annoying your neighbors.
Seasoning wood has another important but less obvious benefit—when wood is properly cut and stacked right away, mold has less opportunity to establish itself. Throwing unseasoned firewood into a pile allows mold to spread throughout the logs, mold that you unwittingly release into your home’s environment when you bring the firewood inside throughout the heating season.
You can buy already seasoned firewood or buy it green and season it yourself. How can you tell whether wood is properly seasoned? It's possible to test the wood with a moisture meter, which measures resistance to a small current and converts it into a moisture-content reading, yet this reading can vary widely from one area of the log to another. With a little practice, however, you can use the following tips to judge accurately for yourself whether your wood is dry. Use as many as you can for the best results.