Maine Firewood Values in BTU

Heat Values for Common Maine Firewood.

I grew up with a couple of woodstoves, and have gotten used to "just knowing" which wood is best for heating the house, and how much heat I'll get from a particular stove-load of firewood. I can tell how long I have before I should look at stoking the fire again, by what I've put into it, and how well it's burning. This becomes second nature after a while, honest. If you are new to wood heat, it may seem like just too many variables, too many maybes. Sometimes you go to bed with a stove full of wood and wake up to good coals, sometimes it's all gone by morning. Trust me, it will make sense after a while.

The heat generated by burning wood is measured in BTUs, or British Thermal Units. Briefly, a BTU is the amount of heat needed to raise a pound of water from 39 degrees to 40 degrees fahrenheit. Most of the world measures heat by joules, but the BTU hangs on in talk of furnaces and wood-stoves. Specifically, firewood is rated in milllions of BTUs per cord. To complicate things a little further, there's the factor of how much of the heat is expended vaporizing the water contained in the wood. Now to be frank, I ran into this in my research and thought, Huh. the heat doesn't leave the house other than up the chimney, whether it's vaporizing water in the wood or not. Why should it matter? I found lists showing the effective heating of wood after considering this factor, lists that showed the raw heat availability, and lists that showed both. Some of them seemed to conflict with my experience of the heating utility of the kinds of wood that I'm used to. The sources that most closely match my experience, using the wood I almost always burn, yield these results. In Maine, most of what your likely to burn is listed here, with the best heat-providers at the top.

To be clear, if you burn softwood, like dry pine or cedar, it will burn hot. But it will burn up and become ash very quickly, compared to the hardwoods. I include hemlock because it lasts a bit longer than that, and is a good wood to include in your firewood mix to use for morning fires, just getting the heat going quickly.


There are considerations, of course. Poplar starts to rot very quickly if it is not split right away, same as all kinds of birch. Hornbeam and oak, while great heat sources, are best added to a fire that is already hot and underway. It is much easier to start a fire with hemlock and maple. Smaller pieces burn up faster than bigger pieces. If you are new to wood heating, at least try to get the hang of this; when you are there to tend it, run a smaller fire, but hotter (more air, more flame). Tend it often, adding just a stick or two. This will be quick, hot fire that will be better for your chimney, and honestly more enjoyable to look at. When you go to bed, or when you leave for work, stuff your stove with larger pieces of wood from the top of this list, and give it less air. It will burn slowly, but long. The downside of those long burns is the creosote buildup in your chimney. You can combat this by running the fire hotter when you are at home.

 Another consideration is that while oak and ironwood are your greatest heaters, they also grow slowly, ironwood especially so. You can't use several cords of ironwood annually for very long before you run out of it, and have none left growing. A variety is good, and leaving the right blend of younger trees behind to mature is also good.