How to Choose Firewood that is Safe for Your Chimney
Maintenance of your chimney is important as a safety precaution. The narrow passage through which combustion materials are carried out of your home can be clogged by creosote, among other things. Other than installing a chimney cap with mesh that keeps animals, debris, and rain out, the one thing you can control in your chimney is how much creosote is deposited in the flue. What you burn in your fireplace or wood stove is the main factor which determines the amount of creosote in your chimney.
Dangers of Creosote
For homeowners with chimneys, creosote is something to take seriously. Creosote is a brownish tar-like deposit. It is highly flammable and can be ignited by embers in the chimney lining. If not removed in a timely manner, creosote takes on a second and then a third form, each of which is more difficult to clean and remove than the one before.
In its initial stage, creosote has a high percentage of soot. Soot consists mostly of carbon and is a black flaky or powdery substance. Stage one creosote is easily removed using a chimney brush during an annual chimney cleaning. The second stage looks like black glistening flakes and is largely composed of hardened tar; it is more difficult to remove but can be done. The third stage of creosote looks like tar has been poured down the chimney. It is extremely difficult to remove; until it is removed, it poses a danger of creating a persistent chimney fire.
Minimizing Creosote with Firewood Choices
There are two things about firewood to consider, when trying to reduce the amount of creosote that will be deposited in your chimney: moisture and density.
Trees are about 45% moisture when they are first cut, and the firewood should ideally be about 12% moisture. When firewood is properly dried out, it is referred to as “seasoned firewood.” The process of drying out firewood is normally achieved by stacking it in a way that it can benefit from air and sunshine while being protected from rain. Depending on the type of firewood and the method of drying, it can take about six to twelve months to season it. The reason it’s important to avoid burning unseasoned firewood is because when there is a lot of moisture, gallons of acidic moisture are released into your chimney. The acidic deposits together with creosote are highly flammable and can accelerate deterioration of your chimney lining.
The two types of firewood are softwood and hardwood. Softwood burns more quickly and therefore produces less heat, which means that it can leave behind more creosote in the chimney. To produce hotter fires and greater warmth, dense hardwood should be used because it basically requires twice the softwood to produce the same amount of heat.
The recommended method for keeping a close watch on the creosote in your chimney is to get your chimney inspected by a professional chimney sweep annually. Have the chimney cleaned, as needed, to prevent creosote from advancing into more difficult and dangerous forms.