I don’t know about where you live, but over here we’ve had an exceptional warm winter. So far we’ve had one week or so where temperatures dropped below freezing, but that doesn’t mean we haven’t made good use of our fireplace. That’s why for the month of February, all news will revolve around fire, one way or another. Let’s start with the fuel!
A little science
It’s basic chemistry everybody has seen at one stage during their time in the school system. To sustain a fire, you need three things:
- Something combustible, also known as the fuel
- Oxygen, used to actually burn said fuel.
- A source of ignition, usually a match or lighter, to fire the whole thing up.
One quick word about that oxygen before we move on: do not underestimate the amount you will be going through. That’s why an external supply of air really is recommended, if not present you’ll just suck cold air into the room you’re trying to heat (or worse, your fire will produce carbon monoxide…).
Enough of the science, on to the fun stuff: wood! There are many trees out there, each with their specific properties. For burning usage, what matters most is its density. The higher the density, the more a certain log weighs and the more energy is stored in it. This in turn means that log will burn longer and slower, due to the material being closer together which makes it harder to reach for the oxygen. As a rule of thumb: the longer it takes a tree to grow a certain size, the heaver the wood should be.
So, the heavier the better, right? Throw on a log every half hour and you’re set? Well, it depends. It depends on the type of fire you have or want.
If you have an open fireplace, or you want to build a camp fire, then yes, the heavier the better (the same goes for pretty much every fireplace where you have to keep the fire going if you still want its warmth). Oak, beech and ash are commonly sold around here for that purpose. In my experience it’s safe to say that wood purchased without explicitly mentioning the use should be fine.
However, as you might remember, we had to get something other than a regular stove: we got a heat-accumulating soapstone stove. And that changes the game. Completely.
In such a stove you want the fire to burn as fast and as hot as possible. This means either smaller pieces (which gets impractical really fast, as you’ll be constantly throwing wood on the fire), or a different kind of wood. When we ordered our stove, the seller recommended birch. Another option I’ve encountered when looking for wood for our stove is poplar. As that’s a whole lot lighter than birch, I’m not really convinced that the amount needed won’t be huge (instead of being just, well, large…). For now I’ve settled on trying to find birch for next winter. Or pallet wood (which should be fine too).
The amount of wood we got from our roof is vaporizing as I type, so for next winter I’ll need to get a new supply one way or another. The most economical way would be to get a patch of land with birch trees on it, plant new ones every year to make up for the ones I take down. Unfortunately I don’t have the time nor the skills to take down a tree safely, cut it all up in pieces and let it dry for a year or two. Nor do I have said patch of land. To buy wood, I must.
Again, this depends on the type of stove and the usage of it. For soapstone stoves I found a rule of thumb: if you fire it up every day, then you should provide roughly 1 kg of wood for every 100 kg the stove weighs. Our stove weighs roughly 1800 kg, so we need to feed it around 18 kg of dry wood daily (fun fact: for three months I kept records on how much weight I dropped in, and guess what, exactly 18 kg per day on average).
Now things get funny. You can’t just call up your local wood delivery guy and ask him to swing by and drop, let’s say, 200 x 18 kg of birch (yes, that’s 3,6 tonnes of wood, gone in a year!). It doesn’t work that way. They use a special unit called the stère. One cubic metre of wood blocks. But how much does a stère weigh?
First of all we have to take into account the air and empty space in a stère. Roughly 67% of it is wood, depending on how well it has been stacked, what length it has been cut into, etc… If I want birch, which weighs around 600 kg per cubic metre, then I get around 400 kg per stère, or I need 9 stère of birch for a year. Same exercise with oak: 750 kg per cubic metre, so 500 per stère or 7 stère in total needed.
To complicate things even more, some sellers work with cubic metres instead of stères, as they claim they can pile the wood so close that it actually is close to a cubic metre. Makes you wonder why the stère is still in use…
Once you have a pile of wood, delivered to your door preferably, you still need a solution to store it through the year. Ideally this should be a sunny spot, but still free from rain. Oh, and windy too, if possible. Your bottom row should be a little off the ground too, to prevent it from soaking up water. A trick I’ve encountered a number of times for this is to have a pallet upon which you start (or more than one as your stock can get larger than what fits on one pallet).
So you want a roof, large enough, with tilted siding so the wind can get through but the rain cannot, and pallets on the floor. If you’re building it against a wall, you best leave some space between your wood and the wall too. Or try hanging a pallet against it first.
Last but not least: how long do you need to store your wood for it to be perfect to burn? Again, it depends. First of all the size of the logs plays a role: the smaller they are cut, the faster they’ll dry out. Next is the moisture content. As far as I’ve been able to find, you can get three stages: wet, semi-dry and dry wood (from cheapest to most expensive). The only difference is the time the sellers has been able to store it himself. As a rule of thumb, take one summer to advance a stage, so to go from wet to dry you’ll need to be able to store it for two summers (and obviously the winter in between). If you have the space available, it can pay off though, as prices per stère go up 10–20% for each next stage…
Heating your house with wood can be very rewarding: the glow of the fire, the pleasant heat. However, it is not as convenient as heating with gas or oil: you need to plan your supply, you need to maintain the fire. We kicked of fire month with the first thing you need: wood. If sourced right, wood can be more economical and ecological as a source of heat than fossil fuels. I know I am willing to make the trade-off and invest a little of my time in it, do you too?
Be sure to check back next week, when we’ll be actually starting fire! Or just shoot any questions you might have in the comments below!