If you have a wood burning stove, now is the time to be thinking about next winter’s fuel.
If you’re an experienced woodburner, you may well have bought it in last year, and would be sitting with your feet up feeling smug if you weren’t already worrying about the famously hard winter of 2013/14 and how much fuel you’re going to need to see you through that. At any rate, you probably won’t be reading this blog.
The principle of the matter at hand is that, unless you buy kiln-dried, chances are your new load of wood is going to need more seasoning before you burn it; a lot more seasoning if you buy it green, less if you’ve bought what your supplier calls ‘seasoned’ (it’s probably been ‘seasoned’ in a pile in a dark barn).
All wood should be seasoned before burning as fuel; many woods will more than halve in mass as they dry out, while some, like ash, start out as low as 35% moisture (you want your wood to be around or under 25% ideally. In practice, it can be difficult to get lower than this in a maritime climate like the UK because the wood re-absorbs moisture from our damp air). If you let the sun and the wind do the hard work, you get to enjoy all the calorific value of what’s left. If you expect your stove to dry it out, you’ll have to boil out that water content before you get any appreciable heat from whatever’s left, as well as coating your flue in a nasty thick layer of tar and probably blackening up your stove window in the process.
Woods that start out with a low moisture content can be ready to burn after just one summer (or ‘season’). Softwoods, although less dense, have a different physical structure to broad-leafs, as well as being more resinous, and may require extensive seasoning. Removing the bark and chopping your wood to narrow diameter will help speed up the process. Store the wood facing the sun, preferably in an airy lean-to, and for ease of access, not too far from your stove! The best place is often where you have your outdoor seating area, but usually a compromise between chief woodburner and chief sunbather can be negotiated.
When a log is dry, the bark should come away fairly easily in your hand, the wood will have split as the fibres dry out, and rather than hearing a heavy thud when you strike two lengths together, you should get more of a hollow ringing sound. Alternatively, you can buy a moisture meter. Stick its prongs into a freshly split log and you’ll get a digital measure of its moisture content.
Once your fuel is seasoned, all you have to do is burn it properly. Burnt at high temperature, wood gases will ignite, unlocking a high percentage of a log’s calorific value. If you smoulder wood, either in a misguided attempt to eke out your fuel supply, or to keep your stove in overnight, you’re asking for trouble: instead of helping to keep you warm, those same gases will condense on any cool surface between your stove and the top of the chimney pot, releasing noxious odours and locking down their latent energy for a future chimney fire. Pictured below is the result of one such unfortunate’s history of wood-smouldering: the six-inch flue is reduced to a tiny gap by the build-up of tar.
So if you want to avoid the same predicament, 1. Season your wood, 2. Burn it properly, 3. Get your flue swept regularly. Amen.