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Thursday - December 04, 2014

From: austin, TX
Region: Southwest
Topic: Trees
Title: Is it safe to burn Cedar in a fireplace?
Answered by: Guy Thompson

QUESTION:

Is it safe to burn Cedar in our fireplace? I'm trying to thin out the population of Ashe Junipers on my property in Spicewood Tx. to give the young Live Oaks a chance to compete for sunlight and water. I can cut them down quickly, but I can't haul them out fast enough. The cut Cedar has been stacking up pretty fast. Meanwhile, I have a wife and daughter who love to sit by our wood burning fireplace. I love to indulge them, so I've been hauling in bundles of rather expensive cut firewood. Ironically, most of it looks like Live Oak. We'll go through a lot in the winter months. I can't haul it in fast enough. This whole arrangement strikes me as ridiculous. I've heard that you should only burn hardwoods in your fireplace, but I haven't found any evidence to support that. The internet is overrun with conflicting information from sources of questionable authority on the subject. Some say Cedar lights quick and makes great firewood. Others say it's concentrated with oils that can build up in your flue or even cause flash fires. I want to do the sensible thing, but I don't want to risk burning my house down. What does Mr. Smarty Plants say? Your authority and that of the Lady Bird Johnson Wildflower Center are above reproach around here. Can you give me a definitive answer? Please help.

ANSWER:

Mr. Smarty Plants knows more about growing plants than burning them. However, after reading what the experts say, I feel that it is safe to burn cedar Juniperus ashei (Ashe juniper) under the right circumstances. I have been burning cedar, usually mixed with oak, for years and have not seen a creosote buildup in my flue.

It is important to burn cedar that has been cut into approximately 2 foot lengths and seasoned for at least 9 months. This allows much of the moisture to escape from the wood. If the wood is burned "green", it will burn cooler because much of the fire's heat will be used the evaporate the substantial amount of water present in freshly cut wood. This cooler fire will volatilize much of the natural oil rather than burning it, and these oils could then end up settling as creosote deposits in the flue. See the discussion at this web site.

The key, therefore, is to have a hot-burning fire. A good plan is to use a mix of well-seasoned cedar, which is fairly easy to get burning, and seasoned oak, which has fewer oils and gives a more sustained, but still hot, burn. However, avoid such a huge fire that flames leap up into the flue, where even traces of creosote could ignite.

Every fireplace is different from the rest. So you should make an annual inspection of your flue for any sign of a creosote buildup.